Examining social isolation and loneliness in combination in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

Verena H Menec; Nancy E Newall; Corey S Mackenzie; Shahin Shooshtari; Scott Nowicki

doi:10.1371/journal.pone.0230673

. 2020 Mar 23;15(3):e0230673. doi: 10.1371/journal.pone.0230673

Examining social isolation and loneliness in combination in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

Verena H Menec ^1,^*, Nancy E Newall ², Corey S Mackenzie ³, Shahin Shooshtari ¹, Scott Nowicki ¹

Editor: Simone Reppermund⁴

PMCID: PMC7089537 PMID: 32203553

Abstract

Background

Although a large body of research has focused on social isolation and loneliness, few studies have examined social isolation and loneliness together. The objectives of this study were to examine: 1) the relationship between four groups derived from combining social isolation and loneliness (socially isolated and lonely; only socially isolated; only lonely; neither socially isolated nor lonely) and the desire for more social participation, and social support; and 2) the relationship between the four groups and psychological distress.

Methods

The study was based on the Comprehensive Cohort of the Canadian Longitudinal Study on Aging. Using CLSA baseline data (unweighted N = 30,079), ordinary and logistic regression analysis was used to examine the cross-sectional relationship between the four social isolation/loneliness groups and desire for more social participation and four types of social support (tangible, positive interaction, affection, and emotional support). Prospective logistic regression analysis was possible for psychological distress, which was derived from the Maintaining Contact Questionnaire administered about 18 months after the baseline questionnaire (unweighted N = 28,789).

Results

Findings indicate that being socially isolated and lonely was associated with the most social support gaps; this group also had an increased likelihood of psychological distress, relative to those who were neither socially isolated nor lonely. Participants who were only socially isolated, and those only lonely also perceived some social support gaps. In addition, the only lonely group was more likely to be psychologically distressed than the only socially isolated group and the neither isolated nor lonely group.

Conclusion

Examining the four social isolation/loneliness was useful, as it provided more nuanced risk profiles than would have been possible had we examined social isolation and loneliness separately. Findings may suggest avenues for interventions tailored to the unique needs of at-risk individuals.

Introduction

Social isolation and loneliness have been studied extensively over the past four decades, with numerous studies showing that both have negative mental and physical health consequences [1–5]. Similarly, the factors that place people at risk of social isolation and loneliness have been studied extensively [6–8]. Policy makers are also increasingly recognizing that social isolation and loneliness are important public health concerns that need to be addressed. In Canada, the federal government has allocated funding for projects designed to reduce social isolation [9]. The United Kingdom has launched a loneliness initiative and implemented a Minister for Loneliness [10]. As part of this initiative, physicians will be able to offer “social prescribing” and direct patients to community workers who provide tailored support, for example.

Recently, we [11] argued that examining loneliness and social isolation in combination may provide important insights into people’s social needs, and possible interventions that cannot be gained from examining the two concepts separately. The present study was designed to examine the association between four groups derived from combining social isolation and loneliness, and social factors and mental health in a sample of middle-aged and older Canadians who participated in the Canadian Longitudinal Study on Aging (CLSA). More specifically, given the CLSA data that were available at the time this study was conducted, we examined the cross-sectional relationship between social isolation and loneliness groups in relation to desire for more social participation, and perceived availability of social support, as well as their prospective relationship to psychological distress.

Conceptualizing social isolation and loneliness

Consistent with previous literature, we conceptualized social isolation, loneliness and social support by drawing on distinctions between the structure (e.g., number of contacts; frequency of contact) and function (social support) of social networks [2,12–14], as well as the differentiation between objective assessments versus subjective perceptions of social relationships [14–16]. In line with this literature, social isolation can be defined in terms of people’s social network structure, reflective of the objective state of a lack of social relationships [16]. In contrast, loneliness is typically defined as a subjective phenomenon that reflects the perception that emotionally intimate needs, or social needs are not being met [15–17]. As suggested by the discrepancy perspective of loneliness, loneliness arises when there is a mismatch between the quality and/or quantity of social relationships that people have versus what they want [17]. Hence, a person could be lonely despite having a relatively large social network, or be socially isolated and not feel lonely. That the two concept are distinct is supported by several studies that show that they are only weakly correlated with each other [18–21].

The health-related outcomes of social isolation and loneliness

It is well established that social isolation and loneliness are health risks. For example, social isolation is associated with an increased risk of coronary heart disease and stroke [5], dementia [22], and mortality [2]. That social isolation is as much a risk factor for mortality as other well-known lifestyle risk factors, such as smoking, was noted over 30 years ago [12], a conclusion that was reiterated more recently on the basis of a meta-analysis of over a hundred studies [2]. Loneliness has also been shown to be associated with a wide range of physical and mental health outcomes, such as reduced cognitive function [23], depression [24–26], and mortality [3]. Moreover, both social isolation and loneliness have been shown to be related to negative health-related behaviors, such as reduced physical activity and smoking [24,27–29], as well as physiologic responses, including increased blood pressure and heightened inflammatory reactivity to stress [30–34]. Health behaviors and physiologic mechanisms are likely, in part, responsible for the negative health outcomes associated with social isolation and loneliness [31–34].

The relationship between social isolation/loneliness and social support has also been examined extensively, as it may be an important factor that ultimately leads to poor mental or physical health outcomes [12,34–37]. Social support refers to the types of assistance or help social network members provide, such as instrumental support with everyday tasks, or emotional support [12,13,36]. Both loneliness and social isolation are related to reduced social support availability [25,26]. For example, in a recent study, we [38] showed that a restricted social network structure, reflective of social isolation, was negatively related to several types of social support, including instrumental or tangible support (e.g., help with activities of daily living), emotional/informational support (e.g., having somebody to talk to or confide in), positive interactions (e.g., having somebody to have a good time with), and affectionate support (e.g., having somebody who gives love or affection). Lower perceived availability of certain types of social support was, in turn, related to increased depressive symptoms [39], a finding that is consistent with numerous studies that show that perceptions of having social support available is protective against depression [25,40].

Social isolation and loneliness groups

Researchers have recommended that social isolation and loneliness should be examined together [3,21], and the two variables are sometimes included simultaneously in analyses [20,21,27,29,41–43]. However, few studies to date have examined the combined effect of social isolation and loneliness on health and health-related outcomes [11].

Victor and colleagues [44], based on research conducted in the 1950s and 1960s reported the prevalence of four social isolation/loneliness groups as 69% for people who are neither socially isolated nor lonely, 22% for the only socially isolated, 6% for the only lonely, and 3% for the socially isolated and lonely. However, no further information was provided regarding the four groups, such as how they differ in terms of their socio-demographic make-up or health outcomes.

Recently, Smith and Victor [45], using clustering analyses based on measures of social isolation, loneliness and living alone, found six groups of people. The largest group (47% of the sample) experienced no loneliness or social isolation. This group also had the least physical health problems and depressive symptoms. On the opposite side of the spectrum, a small proportion (4%) of the sample were both lonely and socially isolated and had a substantially increased likelihood of physical and mental health problems, relative to the majority group. In between these two extremes were four groups that experienced either social isolation or loneliness. These groups were also more likely to have physical and mental health problems compared to the majority group. How these groups fared relative to each other on physical health or mental health was not examined, however.

In other relevant research, social isolation and loneliness were treated as continuous measures, and researchers examined how the interaction between the two measures relates to various social and health outcomes. Lee and Ko [46] examined the interaction between social isolation and loneliness in relation to people’s social interactions. Among other measures, they assessed in detail the types of social interactions participants had in their daily lives, including whether they considered the persons they interacted with as ‘weak’ or ‘strong’ social ties. Results showed that greater loneliness, combined with a large social network was related to having fewer strong social network interactions. In other words, participants who were lonely, but not socially isolated, tended to have social interactions, but not with individuals they felt close to. From an intervention perspective, this suggests that these individuals may benefit from establishing new, meaningful relationships after, for example, loss of a spouse [46,47].

In other studies, researchers examined whether social isolation interacts with loneliness to impact mortality [18,20,48]. Beller and Wagner [18] showed a significant interaction, with the effect of social isolation becoming stronger at higher levels of loneliness, suggesting that being both socially isolated and lonely confers a much higher mortality risk than being only socially isolated or only lonely. However, no significant interaction between social isolation and loneliness on mortality was found in other studies [20,48].

The present study

In the present study, we explored the relationship between social isolation, loneliness and social and mental health variables. Consistent with previous research [20,49–54], we treated social isolation and loneliness as dichotomous, rather than continuous variables, to create four social isolation/loneliness groups: 1) the ‘socially isolated and lonely’; 2) the ‘only socially isolated’; 3) the ‘only lonely’; and, 4) the ‘neither socially isolated nor lonely’. We took this approach, as it allows identifying individuals who might be most at risk of experiencing social support gaps and psychological distress and who may benefit from interventions that are tailored to their needs [55].

The objectives of this study were to examine:

the cross-sectional relationship between the four social isolation/loneliness groups and the desire for more social participation, and social support; and,
2. the prospective relationship between the four social isolation/loneliness groups and psychological distress.

First, we focused on the desire for more social participation to gauge whether individuals in the different groups would actually want more social contact. Social isolation and loneliness interventions presume that people desire more social interaction; if they do not, however, then offers of help may be declined [11]. This issue is particularly relevant for the only socially isolated group, a group that has a small social network but does not feel lonely. Are individuals in this group perhaps choosing to have a small social network [47]? Given that they do not feel lonely, this group may lack the impetus to look for more social contact. Cacioppo and colleagues [31] argued that loneliness, like physical pain, serves an important role by functioning as an aversive signal that motivates people to reduce its negative consequences. Hence loneliness serves as a motivator to seek more social contact. If that is the case, then the only socially isolated may express little desire for more social participation, which may make them a difficult to reach group for interventions.

We hypothesized, therefore, that both the neither socially isolated nor lonely group and the only socially isolated group would be the least likely to want more social contact, but would not differ from each other. In contrast, given the double risk of social isolation and loneliness, the socially isolated and lonely group was expected to be the most likely to want more social interaction. The only lonely were also expected to want more social participation than the neither socially isolated not lonely and the only socially isolated, but less so than the socially isolated and lonely group.

Second, we examined the relationship between the four social isolation/loneliness groups and different types of social support (tangible, emotional, affective, and positive social interactions) [38,39,56], given the importance of social support in people’s mental health [40]. Given that both social isolation and loneliness have been linked to less social support [25,38,39], we expected that the neither socially isolated not lonely group would report the most social support availability and the socially isolated and lonely group the least. As such, the socially isolated and lonely group, was expected to be the most at risk, similar to previous research that shows that social isolation and loneliness have a synergistic effect [18,45]. In considering the two middle groups (the only socially isolated and only lonely), we took into account that perceptions of social support, like loneliness, reflect individuals’ appraisal of a situation [57]. We therefore expected loneliness to be more strongly associated with perceptions of social support than social isolation, with the only lonely group consequently reporting lower social support availability than the only socially isolated group.

Lastly, we examined whether the four social isolation/loneliness groups differ in terms of predicting psychological distress. As such, we build on an extensive literature that has examined social isolation and loneliness in relation to mental health [1,21,24,58]. Psychological distress includes symptoms of both depression and anxiety [59–61]. Given its association with psychiatric disorders and use of mental health services, psychological distress is frequently used as a measure of mental health in population studies [61,62]. Similar to social support, we expected the neither socially isolated nor lonely group to be least at risk of psychological distress and, conversely, the socially isolated and lonely group to be most at risk. The only socially isolated and only lonely were, again, expected to fall in between these two extremes, with the only lonely group expected to report more psychological distress than the only socially isolated group, given the strong association between loneliness and mental health [1,58].

The hypotheses can be summarized as follows:

Neither socially isolated nor lonely group = only socially isolated < only lonely < socially isolated and lonely for desire for more social participation.
Neither socially isolated nor lonely group > only socially isolated > only lonely > socially isolated and lonely for social support.
Neither socially isolated nor lonely < only socially isolated < only lonely < socially isolated and lonely group for psychological distress.

Methods

Data source

This study was based on data from the Canadian Longitudinal Study on Aging (CLSA) [63–65]. CLSA consists of a Comprehensive cohort and a Tracking cohort. Both cohorts were 45 to 85 years of age at baseline. Exclusion criteria for participation in CLSA were: not being able communicate in one of the two national languages (English or French); cognitive impairment at time of contact; resident of the three territories; full-time member of the Canadian Armed Forces; resident in a long-term care institution at the time of recruitment; and living on Federal First Nations reserves or other First Nations settlements. All participants provided written consent for participation in the study. Further information about the CLSA and participant recruitment is published elsewhere [63–65].

In the present study, only the Comprehensive cohort was used (see below for rationale). The Comprehensive cohort consists of participants who were randomly selected within age/sex strata from among individuals residing within 25 to 50 kilometers of a CLSA data collection site in eleven locations across Canada (Victoria, Vancouver, Surrey, Calgary, Winnipeg, Ottawa, Hamilton, Montreal, Sherbrooke, Halifax, and St. John’s). The participants were first interviewed in their own homes with computer-assisted interview instruments and subsequently came to a data collection site for additional computer-assisted interviews and comprehensive assessments, such as physical measures, and to provide biological samples.

Baseline data for the Comprehensive cohort were collected between May 2012 and May 2015. Approximately 18 months following the baseline interview, all participants (Comprehensive and Tracking) were re-interviewed via computer-assisted telephone interviews with the Maintaining Contact Questionnaire (MCQ). At the time the present study was conducted, only CLSA baseline data and data from the MCQ were available. The MCQ contains questions not asked at baseline. Although most of the measures in both the baseline and MCQ questionnaires are identical for Comprehensive and Tracking participants, some measures are included in one cohort only. This is the case for psychological distress, which was assessed only in the MCQ of the Comprehensive cohort. Because psychological distress was a key outcome measure in this study (and no other mental health measure was available in the MCQ), we restricted our analyses to the Comprehensive cohort. This allowed for an 18-month prospective analysis for psychological distress. As desire for more social participation and social support are assessed at baseline only, and are not included in the MCQ, analyses are cross-sectional for these outcome measures.

The present study received ethics approval from the University of Manitoba’s Health Research Ethics Board. Data access was approved by the CLSA Data and Sample Access Committee.

Study sample

The baseline data of the CLSA Comprehensive cohort contains 30,079 participants, representing over 3.7 million Canadians. Of these participants, 28,789 completed the MCQ. Given missing values on some measures, the actual sample size used differs somewhat across measures (see Analytic approach section for further information).

Measures

Social isolation/loneliness groups

Four social isolation/loneliness groups were created by combining measures of social isolation and loneliness. Social isolation was defined based on a social isolation index that was derived based on individuals’ contact with different social network groups. Including different social network groups is consistent with previous research that shows that a variety of social network members play an important role in people’s lives, ranging from family members (spouses, children, siblings) to other relationships (friends, neighbors) [38,39], Similar to previous research [20,29,41,53,54], we allocated one point when each of the following conditions applied: 1) living alone and not married or in a common law relationship; 2) got together with friends or neighbours “within the past 6 months” or less frequently, or reported having no friends or neighbors; 3) got together with relatives/siblings “within the past 6 months” or less frequently, or reported having no relatives or siblings; 4) got together with children “within the past 6 months” or less frequently, or had no children; 5) being retired and having participated in none, or only one of eight social activities at least once a month or more often (e.g., family or friendship based activities, church or religious activities, sports or physical activities, and educational and cultural activities) (for a more detailed description see 53 and 54). The resulting social isolation index ranged from 0–5, where higher scores reflect greater social isolation. The index was subsequently dichotomized. To allow a sufficient sample size in each of the four groups, individuals with scores 2 or more were classified as socially isolated and those with 0 or 1 as not socially isolated, similar to previous research [20,27,54].

The CLSA baseline questionnaire does not contain a loneliness scale. We therefore used a single-item loneliness question that is part of the CES-D10 depression scale [66]: [Over the past week] “How often did you feel lonely?” (1 = all of the time [5-7days]; 2 = occasionally [3–4 days]; 3 = some of the time [1–2 days]; 4 = rarely or never [less than 1 day]. Similar single-item measures are commonly used in the literature [1]. The item was dichotomized, with “all of the time” and “occasionally” responses classified as lonely and the remaining categories as not lonely.

The dichotomized social isolation index and loneliness measure were subsequently combined to create four groups: neither socially isolated nor lonely; only socially isolated; only lonely; and neither socially isolated nor lonely.

Desire for more social participation

In the baseline questionnaire, after responding to the eight questions related to social participation (see above for description), individuals were asked: “In the past 12 months, have you felt like you wanted to participate in more social, recreational, or group activities?” Yes/no.

Social support

Perceived social support was measured in the baseline questionnaire with the Medical Outcomes Study (MOS)–Social Support Survey [56]. This validated scale contains 19-items that focus on: tangible support (e.g., “someone to help you if you were confined to bed”); positive social interaction (e.g., “someone to get together with for relaxation”); affectionate support (e.g., “someone who hugs you”); and emotional/informational support (e.g., “someone you can count on to listen to you when you need to talk”). Responses are coded as: 1 = none of the time, 2 = a little of the time, 3 = some of the time, 4 = most of the time, 5 = all of the time. Mean scores were derived for each of the four subscales (range = 1–5).

Psychological distress

Psychological distress was measured in the MCQ questionnaire using the 10-item Kessler (K10) scale [59,60]. The scale is designed to assess non-specific psychological distress, with questions focusing on anxiety and depressive symptoms in the previous 30 days; e.g., “How often did you feel nervous?”; “How often did you feel hopeless?”; How often did you feel depressed?” [1 = none of the time; 2 = a little of the time; 3 = some of the time; 4 = most of the time; 5 = all of the time]. Summing across the 10 times creates a score ranging from 10 to 50. Consistent with previous research, we dichotomized the variable, such that participants with scores <20 were considered as having low distress and those with scores > = 20 as experiencing high distress [59,67,68].

Covariates

Several socio-demographic variables were included in the analyses, given their known relationship with social isolation and loneliness [6–8,53,54]. All variables were derived from the CLSA baseline questionnaire: age, sex, education, and household income. Age was categorized into four categories (ages 45–54, 55–64, 65–74, 75–85). Sex was coded as 0 = women and 1 = men. Education was dichotomized as: 0 = secondary school or less, and 1 = at least some post-secondary education. Household income was measured by asking participants to give the best estimate of the total household income received by all household members, from all sources, before taxes and deductions, in the past 12 months. The variable was categorized as 1 = less than $20,000; 2 = $20,000 or more, but less than $50,000; 3 = $50,000 or more; and “missing” for those who did not answer the question.

We also included several baseline health measures (chronic conditions, functional status, and depressive symptoms) in analyses, as physical and mental health is not only an outcome of social isolation and loneliness, but also a predictor [6–8]. For example, chronic conditions predict an increase in loneliness over time [69], and there is a reciprocal relationship between both functional limitations and loneliness, and depressive symptoms and loneliness [70].

The Older Americans Resources and Services (OARS) Multidimensional Functional Assessment Questionnaire [71] was used to assess functional status. The scale includes seven questions related to Activities of Daily Living (e.g., getting out of bed, dressing, and eating) and seven questions related to Instrumental Activities of Daily Living (e.g., using the telephone, shopping, and preparing meals). Participants were asked whether they can complete the task without help, with some help, or are completely unable to perform it. After categorizing individuals as having no functional impairment, mild impairment, moderate impairment, severe impairment, and total impairment, a dichotomized variable was created with: 0 = no functional impairment, and 1 = at least some functional impairment.

Chronic conditions were measured with a list of 33 conditions, such as osteoarthritis, respiratory conditions, and cardiac/cardiovascular conditions. For each condition, participants were asked if a doctor had diagnosed them with the condition. “Yes” responses were summed to create an overall index.

A baseline mental health variable was also included in multivariable analyses. Ideally, we would have included psychological distress as both a covariate and outcome variable. However, as that measure is not available in the baseline CLSA questionnaire, we used a single item from the CES-D10 scale instead: [Over the past week] “How often did you feel depressed?” (1 = all of the time [5-7days]; 2 = occasionally [3–4 days]; 3 = some of the time [1–2 days]; 4 = rarely or never [less than 1 day]. This single item was included, rather than the full CES-D10 scale, given that the loneliness item from the scale was used to derive our four social isolation/loneliness groups. We chose the depression item because it had the highest item to total CES-D10 scale correlation (r = .60). Turon and colleagues [72] recently concluded that a single item depression measure may be useful in ruling out the need for further psychological assessment or intervention.

Analytic approach

Data were analyzed using survey weights provided by CLSA. As recommended by CLSA, we used trimmed weights in the descriptive analyses and analytic weights in inferential analyses [73]. All analyses were conducted using SAS version 9.4. First, we conducted bivariate analyses to compare the four social isolation/loneliness groups in relation to all the other variables. Because we were interested in all possible comparisons between the four groups, we used the LSMEANS option for regression analysis. The option calculated simultaneously all six possible pairwise comparisons between social isolation/loneliness groups. The generated parameter estimates are equivalent to those derived from individual regressions with different reference groups specified. The LSMEANS option for bivariate logistic regression was used to compare the four social isolation/loneliness groups in relation to dichotomous variables (sex, education, functional status, desire for more social participation, psychological distress). The option was used in bivariate ordinal regression involving ordinal variables (age group, household income), and in bivariate ordinary least squares regression for continuous measures (chronic conditions, depressive symptoms, social support). To reduce the likelihood of a Type I error, each set of multiple comparisons was evaluated for significance using a Bonferroni adjustment (p = .01 divided by 6 comparisons = .0017).

Second, the outcome measures (desire for more social participation, social support, and psychological distress) were analysed with the four social isolation/loneliness groups as key predictor using multivariable analyses, adjusted for covariates. The province of residence was also controlled for in these analyses, as recommended by CLSA when using survey weights [73]. Again, the LSMEANS option was used to test all possible comparisons between the four social isolation/loneliness groups, using a Bonferroni adjustment (p = .01 divided by 6 comparisons = .0017). Missing values were deleted list-wise in the multivariable analyses. Missing values were minimal, ranging from <1% to 2.6%.

Results

Descriptive statistics for the sample are shown in Table 1.

Table 1. Sample description.

Measures	Weighted N	Weighted % or Mean	Standard Error
Age groups
Ages 45–54	1,563,066	42.0	0.38
Ages 55–64	1,108,198	29.8	0.31
Ages 65–74	638,899	17.2	0.23
Ages 75–85	407,614	11.0	0.18
Sex
Female	1,869,254	50.3	0.37
Male	1,848,523	49.7	0.37
Education
Less than postsecondary	1,179,197	31.7	0.34
Postsecondary	2,538,392	68.3	0.34
Household income (yearly)
< $20,000	161,709	4.4	0.13
$20,000 to < $50,000	655,621	17.6	0.25
> = $50,000	2,694,978	72.5	0.30
Missing response	205,468	5.5	0.16
Functional status
No functional impairment	3,413,505	92.3	0.18
Mild, moderate, severe, total impairment	286,007	7.7	0.18
Number of chronic diseases	3,744,848	2.94	0.02
Depressive symptom	3,734,419	1.29	0.00
Desire for more social participation
No	1,886,290	50.5	0.37
Yes	1,849,218	49.5	0.37
Social support
Tangible support	3,740,050	4.27	0.01
Positive interactions	3,740,399	4.26	0.01
Affection	3,740,263	4.49	0.01
Emotional support	3,740,602	4.23	0.01
Psychological distress
Low	3,089,408	87.2	0.26
High	455,251	12.8	0.26

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In this sample, 74.7% of participants were neither socially isolated nor lonely, 15.6% were only socially isolated, 6.7% were only lonely, and 3% were socially isolated and lonely (Table 2). Descriptive statistics (and associated bivariate analyses) for the four groups show some differences on covariates. For example, the neither socially nor lonely group was younger than the other three groups, although the latter did not differ significantly from each other.

Table 2. Social isolation/loneliness groups by covariates and outcomes measures: Weighted percentages (within each group) or weighted means.

	Total Sample	Neither isolated nor lonely	Only isolated	Only lonely	Isolated and lonely
	100	74.7	15.6	6.7	3.0
Covariates
Ages 45–54	42.0	44.3^a	35.4^b	37.1^b	32.3^b
Ages 55–64	29.8	29.4	30.4	31.9	31.9
Ages 65–74	17.2	16.5	20.0	16.4	20.3
Ages 75–85	11.0	9.8	14.1	14.6	15.5
Women	50.3	49.6^a	49.9^a	60.0^b	47.9^a
Men	49.7	50.4	50.1	40.0	52.1
Low education	31.7	30.8^a	31.2^a	39.9^b	40.0^b
High education	68.3	69.2	68.8	60.1	60.0
< $20,000	4.4	2.1^a	10.2^b	7.6^b	21.7^c
$20,000 < $50,000	17.6	14.8	25.4	25.3	31.9
> = $50,000	72.5	78.0	58.0	60.4	38.5
No response	5.5	5.1	6.4	6.7	7.9
No functional impairment	92.3	93.7^a	89.6^b	86.4^c	82.2^c
Mild/moderate/severe/total functional impairment	7.7	6.3	10.4	13.6	17.8
Number chronic conditions	2.94	2.79^a	3.23^b	3.58^c	3.76^c
Depressive symptom	1.29	1.2^a	1.26^b	1.90^c	1.95^c
Outcome measures
No desire for more participation	50.5	52.7^a	50.6^a	33.2^b	33.6^b
Desire for more participation	49.5	47.3	49.4	66.8	66.4
Tangible support	4.27	4.41^a	3.93^b	3.89^b	3.30^c
Positive interaction	4.26	4.39^a	4.04^b	3.76^c	3.37^d
Affection	4.49	4.65^a	4.16^b	4.09^b	3.42^c
Emotional support	4.23	4.33^a	4.06^b	3.78^c	3.49^d
Low psychological distress	87.2	89.9^a	86.9^b	66.6^c	62.7^c
High psychological distress	12.8	10.1	13.1	33.4	37.3

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Percentages or means that do not share a superscript are significantly different from each other based on weighted, bivariate least square mean comparisons derived from regression analyses (logistic regressions for dichotomous outcomes, ordinary least squares regressions for continuous outcomes, and ordinal regressions for ordinal level outcomes) using a Bonferroni adjustment (p value of .01/6 = .0017).

Differences between the four social isolation/loneliness groups also emerged for our outcome measures in bivariate analyses (Table 2). For example, the neither socially isolated nor lonely group reported more positive interactions and emotional support than the only socially isolated group, who in turn reported more positive interactions and emotional support than the only group who, in turn, reported more positive interactions and emotional support than the socially isolated and lonely group (see Fig 1). A slightly different pattern emerged for tangible support and affection, in that the only socially isolated and the only lonely groups did not differ from each other. (See S1 Fig for other measures).

We next conducted multivariable analyses for the three outcome measures. As the results shown in Table 3 indicate, including covariates in the analyses did not change the results for desire for more social participation. In both unadjusted and adjusted analyses, the neither socially isolated nor lonely group did not differ from the only social isolated group, but both groups were less likely to desire more social participation than the only lonely and the neither socially isolated nor lonely groups. The only lonely group and the neither socially isolated nor lonely group did not differ from each other.

Table 3. Comparisons of social isolation/loneliness groups for desire for more social participation.

	Desire for more participation (vs. no desire)
Social isolation/loneliness groups	Unadjusted¹	Adjusted
Neither isolated nor lonely vs. only isolated	-0.10 (0.03)	-0.10 (0.04)
Neither isolated nor lonely vs. only lonely	-0.86 (0.05)	-0.78 (0.06)
Neither isolated nor lonely vs. isolated and lonely	-0.82 (0.07)	-0.71 (0.08)
Only isolated vs. only lonely	-0.76 (0.06)	-0.68 (0.06)
Only isolated vs. isolated and lonely	-0.72 (0.08)	-0.61 (0.08)
Only lonely vs. isolated and lonely	0.04 (0.09)	0.07 (0.09)

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¹Parameter estimates are shown and, in brackets, standard errors. The analysis is based on Baseline data, unweighted N = 29,784. Parameter estimates are derived from a weighted logistic regression and test differences in least squares means between groups. Adjusted analyses control for: age group, sex, education, household income, functional impairment, chronic conditions, depressive symptom, and province of residence at baseline. Statistical significance was assessed using a Bonferroni adjustment, p value of .01/6 = .0017. Significant results are bolded.

Multivariable (adjusted) results also mirrored those from bivariate analyses for social support (Table 4) and psychological distress (Table 5). There was only one exception to this pattern. For psychological distress, no difference emerged between the neither socially isolated nor lonely group and the only socially isolated group in adjusted analyses. A sensitivity analysis showed that the results for psychological distress were the same when the baseline depression measure was excluded from the analysis.

Table 4. Comparisons of social isolation/loneliness groups for social support.

	Tangible support		Positive interactions		Affection		Emotional support
	Unadjusted¹	Adjusted	Unadjusted	Adjusted	Unadjusted	Adjusted	Unadjusted	Adjusted
Social isolation/loneliness groups
Neither isolated nor lonely vs. only isolated	0.47 (0.02)	0.39 (0.02)	0.34 (0.01)	0.26 (0.01)	0.48 (0.01)	0.40 (0.01)	0.27 (0.01)	0.20 (0.01)
Neither isolated nor lonely vs. only lonely	0.51 (0.02)	0.34 (0.02)	0.62 (0.02)	0.43 (0.02)	0.54 (0.02)	0.38 (0.02)	0.54 (0.02)	0.37 (0.02)
Neither isolated nor lonely vs. isolated and lonely	1.13 (0.04)	0.87 (0.04)	1.03 (0.03)	0.74 (0.03)	1.24 (0.04)	0.96 (0.04)	0.87 (0.03)	0.60 (0.03)
Only isolated vs. only lonely	0.04 (0.03)	-0.05 (0.03)	0.28 (0.02)	0.17 (0.02	0.06 (0.03)	-0.02 (0.03)	0.27 (0.02)	0.17 (0.02)
Only isolated vs. isolated and lonely	0.66 (0.04)	0.48 (0.04	0.69 (0.04)	0.48 (0.03)	0.76 (0.04)	0.56(0.04)	0.59 (0.03)	0.39 (0.03)
Only lonely vs. isolated and lonely	0.62 (0.04)	0.53 (0.04)	0.42 (0.04)	0.31 (0.04)	0.70 (0.05)	0.59 (0.04)	0.33 (0.04)	0.23 (0.04)

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¹Parameter estimates are shown and, in brackets, standard errors. The analyses are based on Baseline data, unweighted N = 29,644 for tangible support and positive interaction; unweighted N = 29,642 for affection; and unweighted N = 29,645 for emotional support. Parameter estimates are derived from weighted ordinary least squares regression and test differences in least squares means between groups. Adjusted analyses control for: age group, sex, education, household income, functional impairment, chronic conditions, depressive symptom, and province of residence at baseline. Statistical significance was assessed using a Bonferroni adjustment, p value of .01/6 = .0017. Significant results are bolded.

Table 5. Comparison of social isolation/loneliness groups for psychological distress.

	High psychological distress (vs. low distress)
Social isolation/loneliness groups	Unadjusted¹	Adjusted
Neither isolated nor lonely vs. only isolated	-0.30 (0.06)	-0.11 (0.06)
Neither isolated nor lonely vs. only lonely	-1.51 (0.06)	-0.66 (0.08)
Neither isolated nor lonely vs. isolated and lonely	-1.65 (0.08)	-0.65 (0.10)
Only isolated vs. only lonely	-1.21 (0.08)	-0.56 (0.09)
Only isolated vs. isolated and lonely	-1.35 (0.09)	-0.55 (0.11)
Only lonely vs. isolated and lonely	-0.14 (0.10)	0.01 (0.12)

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¹Parameter estimates are shown and, in brackets, standard errors. Psychological distress is derived from the Maintaining Contact Questionnaire; unweighted N in the analyses = 28,042. Parameter estimates are derived from a weighted logistic regression and test differences in least squares means between groups. Adjusted analyses control for: age group, sex, education, household income, functional impairment, chronic conditions, depressive symptom, and province of residence at baseline. Statistical significance was assessed using a Bonferroni adjustment, p value of .01/6 = .0017. Significant results are bolded.

We further conducted sensitivity analyses to determine if results were similar for middle-aged (45–64 years old) versus older (65–85 years old) individuals, and women versus men, respectively (see S1 and S2 Tables). This was generally the case with one exception. Among individuals aged 65–85, no differences emerged between the only socially isolated group and the only lonely group for tangible support, positive interactions, and emotional support. However, the only socially isolated group reported receiving less affection than the only lonely group.

Discussion

Although social isolation and loneliness have been examined alongside each other in previous studies [21,27,29,41,58], there is a paucity of research that has considered the two concepts in combination [18,20,45,46,48]. That differentiating between the four groups could be useful is based on the assumption that depending on whether people are socially isolated or lonely or both, they may have specific social support gaps and needs [11]. Understanding these gaps and needs could, therefore, provide valuable information to help tailor interventions. Conversely, it may help understand how to prevent social isolation and loneliness so that people remain neither socially isolated nor lonely.

The prevalence of the neither socially isolated nor lonely, only socially isolated, only lonely, and socially isolated and lonely groups was 74.7%, 15.6%, 6.7% and 3%, respectively, in the present study. These prevalence rates are quite similar to those reported by Victor et al. [44] for the four groups, which were 69%, 22%, 6%, and 3%, respectively. They are also in line with results by Smith and Victor [45]. In that study, 3.9% of the sample was both socially isolated and lonely and had a high likelihood of living alone. In contrast, less than half of the sample (47%) was neither socially isolated nor lonely. This lower prevalence compared to the findings in the present study could be due to a number of factors, such as different cut-offs to define loneliness (Smith and Victor differentiated between moderately and highly lonely people), the measures included in their Latent Class Analysis (living alone was included as a separate variable), and the analytic approach per se (statistically derived groups versus an a priori classification used in the present study).

The four groups differed on socio-demographic characteristics in the present study, although the pattern of findings was not entirely consistent with previous research across all measures. The neither socially isolated nor lonely group was younger and had a higher household income than the other groups, similar to Smith and Victor’s findings [45], but did not differ from the only socially isolated group in terms of sex and level of education. For the other groups, a few findings stand out. The only lonely group was composed of more women than the other groups, whereas the socially isolated and lonely group had the highest proportion of low-income individuals. In terms of baseline physical and mental characteristics, cross-sectional, bivariate analyses show that the neither socially isolated nor lonely group was less likely to be functionally impaired and had fewer chronic conditions and depressive symptoms than the socially isolated group, who in turn fared better on these measures than the only lonely group and the socially isolated and lonely group. The latter groups did not differ from each other. Overall, the findings suggest that the four groups had unique socio-demographic and health characteristics at baseline.

Turning to our outcome measures, our hypotheses were, in part, confirmed. Our findings indicate that being either socially isolated, lonely, or both, were all associated with some risk. The socially isolated and lonely group was clearly the most at risk group, as expected, consistent with previous research [18,45]. Although this group represents a small proportion of the population, they are an important target for intervention as they have the most social support gaps, and are likely to experience psychological distress. That individuals in this group were also likely to express a desire for more social participation is, on the one hand, positive as it suggests that they are motivated to have more social contact. On the other hand, the finding that a large proportion of individuals in this group are on low income and have health problems suggests that structural barriers to social engagement need to be addressed. For example, making affordable transportation options available could help them attend social programs. Programs that can be accessed from home may be also be appealing to this group. For example, technology interventions whereby individuals receive computer training or social interaction via videoconferencing have been found to reduce loneliness [74,75]. Low-tech, inexpensive approaches, including delivering programs via telephone may also be beneficial, particularly for home-bound individuals [76]. Home visits may also be useful for this group.

The only lonely were the second most at-risk group. This group also desired more social participation, reported some social support gaps and had a high likelihood of psychological distress. This is consistent with previous research that shows that loneliness has health-related impacts even when social isolation is controlled for [42,43]. Given that individuals in this group do not have their social needs met, despite having a relatively large social network, they may benefit from developing new friendships that are more meaningful to them, for example by exploring new activities that expose them to new social networks. For instance, interventions that provide activities, such as visual arts discussion or music participation show promise [74]. Barriers to social participation, such as functional limitations, may also need to be addressed by providing transportation. This group may also benefit from counselling to help improve existing relationships with others. For example, even though these individuals may have a spouse, the marital relationship may be strained, which can have major negative consequences for well-being [77]. This group may also benefit from interventions designed to address maladaptive expectation and social cognitions in relation to the people in their social network [55].

The only socially isolated group was expected to be somewhat at risk as well. Like the only lonely, they perceived some social support gaps relative to the neither socially isolated nor lonely group, but did not want more social participation. Although they were more likely to prospectively experience psychological distress than the neither socially isolated nor lonely group in unadjusted analyses, once we adjusted for baseline socio-demographic and health measures, this difference was no longer statistically significant. These findings suggest that pre-existing sociodemographic and health characteristics associated with social isolation, rather than social isolation per se, predicted psychological distress. This group, therefore, presents a somewhat mixed picture. That they report social support gaps places them at some risk should the need for help arise, a scenario that is not unlikely, given their health problems. That individuals in this group may not want more social contact could, at the same time, make them the most difficult to reach group from an intervention perspective, as they may decline opportunities for more social participation. The potential for these individuals to become lonely therefore exists. In this respect, it would be important in future research to examine people’s group membership over time to determine what factors lead somebody to become both socially isolated and lonely.

The differences that emerged between the only socially isolated and only lonely groups warrant discussion at this point, specifically the differences for the four social support measures. We hypothesized that the only socially isolated would report relatively more availability of all four types of social support than the only lonely group. This hypothesis was only partially supported. As expected, the only socially isolated group reported more positive interactions and emotional support than the only lonely group. To the extent that loneliness reflects not having social needs met, it makes sense that the only lonely group rated their positive interactions and emotional support lower than the only socially isolated. The finding also underscores our conclusion above that the only lonely group could benefit from establishing new friendships. Previous research suggests that positive interaction is gained mainly from friends, rather than family [38].

However, the only socially isolated and only lonely groups did not differ from each other on tangible support. Tangible support focuses on the availability of somebody to help with daily activities (e.g., having somebody to prepare meals or help with daily chores). That the two groups did not differ for this type of support suggests that support with everyday tasks does not depend on the size of the social network [36]; presumably, as long as there is one person available, tangible support needs can, at least to some extent, be met. Another consideration is that we assessed the perceived availability of social support in the present study, not actual support received. An important issue for future research would be to examine what actual support people receive in situations of need. Do the only socially isolated have as much actual social support as they think they have? And what is the actual support available to the only lonely who, even though they have a relatively large social network, are not satisfied with it?

The two groups also did not differ in terms of affectionate support. Affectionate support focuses on having an intimate relationship with somebody; for example, having somebody who shows the person love and affection. Perhaps the two groups showed some affectionate support gaps (relative to the neither socially isolated nor lonely group) for different reasons; the only socially isolated because of their small social network, the only lonely because their social needs are not met, despite having a relatively larger social network. In this respect, it is also noteworthy that, although our sensitivity analyses showed similar results for women, men, and younger individuals, findings were somewhat different for older adults aged 65 to 85. Among these older individuals, the only socially isolated group reported less affectionate support than the only lonely group, but no differences emerged for tangible support, positive interactions, and emotional support. Older adults are at risk of losing their spouse or close friends. Such intimate relationships cannot easily be replaced; however, connecting individuals with social groups may satisfy at least some social needs. Overall, the complex findings suggest that it would be important in future research to gain a more in-depth picture of relationship patterns and social support in different age groups, such as the quality of people’s relationships, actual support received, and who provides support.

Limitations

The present study was based on the Comprehensive Cohort of CLSA only, as psychological distress was measured only in this cohort. The Comprehensive cohort consists of randomly recruited participants residing within a certain radius of data collection sites in eleven Canadian cities. The results of this study may, therefore, not be generalizable to the Canadian population; for instance, our study includes only a small proportion of rural residents. The large sample size may also mean that although effects are statistically significant, they may not be clinically significant. Although CLSA contains measures of participants’ social networks and social support, it does not include measures of the quality (positive, negative) of social relationships and actual support received. We were therefore not able to examine, for example, how the quality of relationships was related to social support gaps and whether, and what types of social support people received. Moreover, we classified participants in an a priori way into the four groups. It would be useful in future research to determine if the same groups emerge using clustering analysis. Using different cut-offs to identify socially isolated and lonely individuals could also change the results. Furthermore, the single item assessing the desire for more social participation does not allow examination of what types of social activities participants would have liked to engage in (e.g., more contact with family or friends, or more group activities). The baseline CLSA data also does not include the Kessler psychological distress scale. As such, we used a proxy mental health item (depressive symptoms) from the CES-D10 depression scale to control for baseline mental health in our prospective analyses. We were able to conduct a prospective analyses for psychological distress in the present study, as this measure was part of an 18-month CLSA follow-up questionnaire. However, this was not possible for social support and desire for more social participation, as follow-up data were not yet available at the time this study was conducted. It will be important in future research to examine social isolation/loneliness, social support, and mental and physical health trajectories over time. Examining whether social isolation and loneliness impacts people differently before and after retirement would also be useful, as retirement represents a major life transition.

Conclusions

We draw several conclusions from our findings. First, examining social isolation and loneliness together was useful, as the findings suggest that there are some differences between the four groups. Second, the study suggests a number of areas for future study. For example, how does group membership change over time and what factors predict these changes? How does the quality (positive, negative) of social relationships intersect with social support and mental health? And what is the relationship between the four social isolation/loneliness groups and other outcome measures, such as physical health or life satisfaction. Third, examining the four social isolation/loneliness groups may suggest avenues for interventions tailored to unique needs. The present study represents a first step in this direction.

Supporting information

S1 Table. Adjusted analyses for middle-aged (age 45–64) versus older individuals (age 65–85).

(DOCX)

Click here for additional data file.^{(19KB, docx)}

S2 Table. Adjusted analyses for women versus men.

(DOCX)

Click here for additional data file.^{(16.5KB, docx)}

S1 Fig. Social isolation/loneliness groups by desire for more social participation and psychological distress.

(JPG)

Click here for additional data file.^{(55.4KB, jpg)}

Acknowledgments

This research was made possible using the data/biospecimens collected by the Canadian Longitudinal Study on Aging (CLSA). Funding for the Canadian Longitudinal Study on Aging (CLSA) is provided by the Government of Canada through the Canadian Institutes of Health Research (CIHR) under grant reference: LSA 9447 and the Canada Foundation for Innovation. This research has been conducted using the CLSA Baseline Tracking Dataset 3.2, Baseline Comprehensive Dataset 3.1, under Application Number 170303. The CLSA is led by Drs. Parminder Raina, Christina Wolfson and Susan Kirkland.

The analyses presented in this paper were funded by a CIHR grant for V. Menec (#373098).

Data Availability

The data used in this study come from the Canadian Longitudinal Study on Aging (CLSA). All interested researchers can access these data through CLSA, subject to review by the Data Access Committee, ethics approval, and signing of a data sharing agreement. Data are provided only once a data sharing agreement is in place between McMaster University (the custodian of the data) and the researchers’ institution. For more information about data access, see https://www.clsa-elcv.ca/data-access. Applications are submitted to access@clsa-elcv.ca.

Funding Statement

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PLoS One. doi: 10.1371/journal.pone.0230673.r001

Decision Letter 0

Simone Reppermund

2 Jan 2020

PONE-D-19-26452

Social isolation and loneliness groups: Associations with social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

PLOS ONE

Dear Dr. Menec,

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: N/A

Reviewer #3: Yes

Reviewer #4: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This is an interesting analysis that examines the meaning of the potential combinations of presence or absence of loneliness and social isolation in an adult population in Canada.

Specific comments

Title: You may consider deleting the word “groups” from the title, because the meaning may not clear to someone who is only viewing the title. It could mean an intervention group for this population. You mean subtypes rather than groups.

Abstract. The referral to “loners” or “lonely in a crowd” is not clear to the reader who has not yet read the introduction.

Page 4. Personally, I do not like the term “lonely in a crowd”. People who have a social network but are lonely are not “in a crowd”, but rather miss a certain intimacy within their social network which may not be that large, but does not qualify for social isolation.

Page 5 “the discrepancy theory of loneliness” sounds more like a definition than a theory.

Page 9, line 171 consider replacing ‘group’ with ‘groups’8

Page 34, in my opinion, the main limitations are not mentioned. Those pertain to

• dichotomizing continuous variables - . social isolation and loneliness are not dichotomous variables and using different cutpoint could change the results.

• Because of the large sample size, effect sizes could be very small despite significant results

• The sample mixes pre-retirement and post-retirement ages despite the differences between those age groups concerning processes concerning loneliness and isolation

• The percentage of lonely people in this sample (6.7%+3%=9.7% line 392 on page 20) is much lower than in most other reports of loneliness, especially in the older population.

Reviewer #2: This paper makes a significant contribution of characterizing the “isolated but not lonely” and the “lonely but not isolated” groups on sociodemographic variables and adjustment outcomes.

Introduction

Overall, the arguments can be streamlined by expressing the meaning of certain sentences and paragraphs more clearly.

1. Line 54: Minister “for” loneliness

2. The sentence from line 61 to 68 is unclear in meaning.

3. Line 71 to 11: it unclear whether the “on the one hand… on the other hand…” comparison meant to characterize the distinction between social isolation and loneliness only, or also between these two terms and social support. Hence the sentence need to be written to improve its meaning.

4. The paragraph from 152 to 161 can be written to express its meaning more clearly. The sentence from line 154 to 156 is particularly unclear.

Methods

5. The way in which participants have been split into four groups can be prone to type 1 error. Do the results hold if the analyses performed were continuous instead of categorical?

6. The authors mentioned that other similar studies have used cluster analysis. Have the authors tried cluster analysis on this dataset to see whether the four groups emerged?

7. Are the variables marital status and living arrangements (e.g. living alone vs with others) available in this dataset? These variables are quite important for studies on social isolation and loneliness.

Results

8. Could graphs be included for all outcome measures?

Discussion:

9. The take-aways, whether in terms of characterizations of or intervention for each group, needs to be made clearer. Currently, the findings read like lists of observations about each group. It will help the readers digest findings if the observations are organized in a more structured and coherent manner.

10. Technology-based interventions for the vulnerable group does not sound realistic or sustainable, given that this group has the largest proportion of “low education” and “low income”. Will regular home visits be a more suitable intervention?

11. Line 534 – 537: “Given that individuals in this group do not have their social needs met, despite having a relatively large social network, they may benefit from developing new friendships.” This sentence does not make sense. Why give people more of what is currently not working for them? It needs to be made clearer how the new friendships are different from existing ones.

12. Line 537: It is curious that the line “As for the vulnerable group…” appeared in the middle of a paragraph ostensibly about the lonely in a crowd group. Is the content in the rest of the paragraph that appears after this line about the vulnerable group or lonely in a crowd group?

13. What are the intervention implications of the results from age-based sensitivity analysis for older adults?

Reviewer #3: It is a great paper about the association of social isolation and loneliness with psychological distress, social support and civic participation. The topic is very interesting and there is a lack in the literature. However some aspects sohould improve:

1.-I think that the introduction should be shorter and focused on the topic (the association between social isolation and loneliness and their effect on civic participation, social support and health)

2.-It would be more clear to call the groups: 1)Neither lonely nor isolated 2)Only isolated 3)Only lonely 4)lonely and isolated.

3.-The authors should clarify the statistical analysis. I think that they used chi squared and anova tests for the comparisons in the descriptive analysis, adjusted and unadjusted ordered logistic regresssions models with the social support outcomes and, finally, adjusted and unadjusted logistic regressions models with participation and psychilogical distress as outcome. I also think that they used diferen sratifications of the samle to compare the effect between sepcific groups. But according to the methods section all this things are not clear.

4.-Authors should also clarify why the analysis wit psicological distress as outcome is prospective (like they say in the introduction)

5.-In my opnion, the main results are that loneliness but not social isolation showed a significant effect on psychological destress as well as that the effect of loneliness seem to be greater than those of social isolation in most of the outcomes.

6.-The authors should make further cites on rellevant literature such as:

Holwerda, T. J., Beekman, A. T. F., Deeg, D. J. H., Stek, M. L., van Tilburg, T. G., Visser, P. J., … Schoevers, R. A. (2012). Increased risk of mortality associated with social isolation in older men: only when feeling lonely? Results from the Amsterdam Study of the Elderly (AMSTEL). Psychological Medicine, 42(4), 843–853. https://doi.org/10.1017/S0033291711001772

Holwerda, T. J., Deeg, D. J. H., Beekman, A. T. F., van Tilburg, T. G., Stek, M. L., Jonker, C., & Schoevers, R. a. (2014). Feelings of loneliness, but not social isolation, predict dementia onset: results from the Amsterdam Study of the Elderly (AMSTEL). Journal of Neurology, Neurosurgery, and Psychiatry, 85(2), 135–142.

Reviewer #4: Review for PLoS One Journal

Social Isolation and Loneliness Groups: Associations with Social Support and Psychological Distress using Canadian Longitudinal Study of Aging (CLSA) Data

The purpose of this paper was to combine measures of social isolation and loneliness to create different groups and determine their association with social support and psychological distress. The four groups created were the majority group, the loner group, the lonely in a crowd group, and the vulnerable group (individuals in this group are dually socially isolated and lonely). In general, the majority group seemed to have the most positive and beneficial associations with social support and psychological distress.

I applaud the authors of this paper as it is innovative and will contribute to the social isolation and loneliness literature. The authors are correct in that many peer-review manuscripts have not examine social isolation and loneliness together, and this aspect of the manuscript alone greatly contributes to its innovation.

In my review of your manuscript, I have found some critiques which I believe will enhance the quality of the manuscript. The biggest issue in my opinion is regarding the methods. More detailed explanations are necessary for the type of analysis utilized, and also differentiating between the cross-sectional analyses and the prospective analyses.

The critiques of your manuscript organized by each section of your paper, from the abstract to the conclusion. I have included line numbers for where I find these issues.

ABSTRACT:

In the methods subsection of the abstract, it would be helpful to include the type of analyses done in the paper. This includes listing which analyses are prospective and which analyses are cross-sectional, and the type of regression modeling utilized (ordinary least squares, logistic, etc.)

INTRODUCTION:

Line 97: This study is actually over 30 years old now, so it should read over 30 years.

Lines 123-125: The authors raise a very important point here, in that most studies have not examined the interactive effects of social isolation and loneliness on health. That being said, the authors should also consider including studies by Cornwell and Waite (2009) and Coyle and Dugan (2012). These studies have simultaneously examined social isolation and loneliness (or Cornwell and Waite’s notion, social disconnectedness and perceived isolation) on health. Please include these studies when covering the literature.

Lines 162-167: Steptoe and colleagues (2013) also examined an interaction effect between social isolation and loneliness on mortality, and the interaction (I believe) was found to be non-significant.

Lines 260-263: There needs to be substantially more information on the amount of missing here. In particular, which measure had the most missing and what measure had the least missing? Were the missing enough to substantially affect the analysis? In general, if the missing are greater than 10%, this can represent a significant problem in the analysis.

Also, how were missing data handled? (I assume through listwise deletion?) If this is the case, then it should be stated.

Also, a final sample size should be stated for each of the analyses.

METHODS

In lines 354-363, the authors discuss having a baseline mental health variable to control for the effects of mental health at baseline. I agree with the authors and think, overall, it would be better to include psychiatric distress at baseline and as an outcome. That being said, I believe it would be helpful to include (in supplementary analyses or aside from the main analyses) another set of analyses without the baseline mental health variable. It would be helpful to do this to determine the consistency of the results and to determine if any of the relationships change.

In lines 380-385: There needs to be a stronger description of the analytic methods used in these analyses. If these are prospective analyses, then that should be stated. For example, if this is a lagged variable analysis or hierarchical modeling analysis, then this should be stated as well.

RESULTS

No changes necessary.

DISCUSSION

Overall, the discussion is written very well.

From lines 537 to 543 is somewhat of a weird transition. A few lines above, it starts with the most vulnerable group, and then it transitions to the lonely in a crowd group. From 537-543, it then goes back to the most vulnerable group. I would suggest discussing one group at a time instead of going back and forth between groups to increase clarity.

**********

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

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PLoS One. 2020 Mar 23;15(3):e0230673. doi: 10.1371/journal.pone.0230673.r002

Author response to Decision Letter 0

28 Jan 2020

PONE-D-19-26452

Social isolation and loneliness groups: Associations with social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

PLOS ONE

Dear Dr. Reppermund;

We have revised our manuscript in line with the two Reviewers’ helpful comments. Below please find responses to the Reviewers’ comments. Please note that the page numbers indicated in our response refer to the unmarked manuscript without tracked changes.

Thank you for re-considering our paper.

Journal requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

________________________________________

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: N/A

Reviewer #3: Yes

Reviewer #4: Yes

________________________________________

3. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #1: Yes

Reviewer #2: No

CLSA data are available via application to the Data Access Committee (see https://www.clsa-elcv.ca/data-access). Data are made available to researchers through a data sharing agreement for the purposes of a specific project and cannot be shared with others.

Reviewer #3: Yes

Reviewer #4: Yes

________________________________________

4. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

________________________________________

5. Review Comments to the Author

Reviewer #1: This is an interesting analysis that examines the meaning of the potential combinations of presence or absence of loneliness and social isolation in an adult population in Canada.

Specific comments

Good point. We have changed the title of the paper to: “Examining social isolation and loneliness together in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data”

Abstract. The referral to “loners” or “lonely in a crowd” is not clear to the reader who has not yet read the introduction.

We are now referring to the four groups more descriptively as ‘socially isolated and lonely’; ‘only socially isolated’; ‘only lonely’; and, ‘neither socially isolated nor lonely’ throughout the paper.

As noted above, we are no longer using any labels for the four groups.

Page 5 “the discrepancy theory of loneliness” sounds more like a definition than a theory.

We have changed this to ‘perspective’, a term that is commonly used in the literature when describing the discrepancy perspective of loneliness (p. 5).

Page 9, line 171 consider replacing ‘group’ with ‘groups’8

This typo has been corrected.

Page 34, in my opinion, the main limitations are not mentioned. Those pertain to

• dichotomizing continuous variables - . social isolation and loneliness are not dichotomous variables and using different cutpoint could change the results.

• Because of the large sample size, effect sizes could be very small despite significant results

• The sample mixes pre-retirement and post-retirement ages despite the differences between those age groups concerning processes concerning loneliness and isolation

We have added these points in the limitations section (pp. 34/35).

• The percentage of lonely people in this sample (6.7%+3%=9.7% line 392 on page 20) is much lower than in most other reports of loneliness, especially in the older population.

The prevalence of loneliness varies widely in the literature, depending on the sample, measure, and cut-off used. Our cut-off is quite stringent; i.e. participants who indicated that they are 3 or more days per week lonely were identified as being lonely. Moreover, our sample included both middle-aged and older adults. Our prevalence estimate of 9.7% lonely is not inconsistent with previous research; e.g., Beutel et al. (2017) found a loneliness prevalence of 10.5% in a sample of 35-74 year olds; Wenger & Burholt (2004), in a sample of older adults, found a prevalence of 9% who were very lonely; and Dykstra (2009) showed a wide range in the prevalence of loneliness across countries: <5% in Denmark; 5-9% in Finland, Germany, Netherlands, and UK; 10-14% in Belgium, France, Ireland, Luxembourg, and Spain; and >19% in Greece and Portugal.

Introduction

Overall, the arguments can be streamlined by expressing the meaning of certain sentences and paragraphs more clearly.

1. Line 54: Minister “for” loneliness

This mistake has been corrected.

2. The sentence from line 61 to 68 is unclear in meaning.

We have revised this section to make the meaning clearer.

We have revised this sentence.

4. The paragraph from 152 to 161 can be written to express its meaning more clearly. The sentence from line 154 to 156 is particularly unclear.

We have revised this section.

Methods

5. The way in which participants have been split into four groups can be prone to type 1 error. Do the results hold if the analyses performed were continuous instead of categorical?

We did not conduct analyses with social isolation and loneliness treated as continuous measures for two main reasons: 1) As noted in the paper (p. 8), social isolation and loneliness are often used as dichotomous variables. This approach, as opposed to keeping then continuous variables, is particularly useful as it allows identifying at-risk individuals who could, potentially benefit from interventions. 2) Creating four groups by combining social isolation and loneliness follows the same logic; i.e. it allows identifying specific groups of individuals who may be at risk. We have now revised the introduction to make this rationale clearer (pp. 8/9).

In terms of type 1 errors, we certainly agree with the Reviewer. This is why we used a conservative Bonferroni adjustment to test for significant differences between the four groups for each of the outcome measures, with each test evaluated at an alpha of .01/6=.0017. That is, our family-wise error rate is controlled at alpha of 01. Given the conservative nature of the Bonferroni adjustment, it is possible that we therefore committed type 2 errors.

6. The authors mentioned that other similar studies have used cluster analysis. Have the authors tried cluster analysis on this dataset to see whether the four groups emerged?

We have at this point not conducted cluster analysis to determine whether the four groups emerged, but simply used an a priori approach to create the four groups we had discussed in a previous, conceptual paper (Newall & Menec, 2018). We recognize that there are many other studies that could be conducted to further explore the four groups. We have added the idea of conducting cluster analysis in the Discussion section (p. 35).

Yes, these variables are in the dataset and were used to create the social isolation variable. See p. 14.

Results

8. Could graphs be included for all outcome measures?

We have added graphs for desire for social participation and psychological distress in Supplemental Figure 1.

Discussion:

We have revised the Discussion and hope this addresses the Reviewer’s concerns.

Technology-based interventions do not need to be expensive or difficult – and can be as simple as using the telephone. We have clarified this in the Discussion (p. 31). Home visits are an option, but would be more resource intensive. We have added home visits as another option in the Discussion (p. 31).

We have revised this sentence to make it clearer that we mean developing new, meaningful social relationships (p. 31).

We have revised this sentence (p. 38).

13. What are the intervention implications of the results from age-based sensitivity analysis for older adults?

We have added a comment regarding this (p. 34).

In response to the Reviewer’s comment, we have streamlined the introduction.

2.-It would be more clear to call the groups: 1)Neither lonely nor isolated 2)Only isolated 3)Only lonely 4)lonely and isolated.

We have adopted the suggested terminology throughout the paper.

We have revised the Analytic approach section to clarify the analyses.

4.-Authors should also clarify why the analysis wit psicological distress as outcome is prospective (like they say in the introduction)

The reason why psychological distress, but not desire for social participation and social support was analyzed prospectively was simply because of data availability. We have clarified this in the introduction (p. 4).

We agree with the Reviewer that loneliness has important health implication, beyond social isolation. We have added a comment to that effect in the Discussion (p. 31).

6.-The authors should make further cites on rellevant literature such as:

We have added these citations.

Reviewer #4: Review for PLoS One Journal

Social Isolation and Loneliness Groups: Associations with Social Support and Psychological Distress using Canadian Longitudinal Study of Aging (CLSA) Data

The critiques of your manuscript organized by each section of your paper, from the abstract to the conclusion. I have included line numbers for where I find these issues.

ABSTRACT:

We have added this information in the abstract.

INTRODUCTION:

Line 97: This study is actually over 30 years old now, so it should read over 30 years.

Thanks for catching this mistake. We have revised this accordingly.

We have added these citations.

Lines 162-167: Steptoe and colleagues (2013) also examined an interaction effect between social isolation and loneliness on mortality, and the interaction (I believe) was found to be non-significant.

We have added this article. The study did, indeed, not find a significant interaction.

Also, how were missing data handled? (I assume through listwise deletion?) If this is the case, then it should be stated.

We have added a comment re missing data (which was less than 3%) and also now note that we used list-wise deletion of missing data (p. 19).

Also, a final sample size should be stated for each of the analyses.

We have added the unweighted sample size in the tables 3-5.

METHODS

We have conducted a sensitivity analysis that did not include baseline depression in the model. The results remain the same (p. 24).

We have revised the methods section to clarify the analyses (p. 18).

RESULTS

No changes necessary.

DISCUSSION

Overall, the discussion is written very well.

We had revised this section (p. 37).

________________________________________

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PLoS One. doi: 10.1371/journal.pone.0230673.r003

Decision Letter 1

Simone Reppermund

27 Feb 2020

PONE-D-19-26452R1

Examining social isolation and loneliness together in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

PLOS ONE

Dear Dr. Menec,

==============================

Please proofread the manuscript very carefully and address the minor changes suggested by reviewer 1. Once these minor edits are corrected, the manuscript will be accepted for publication.

==============================

We would appreciate receiving your revised manuscript by Apr 12 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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We look forward to receiving your revised manuscript.

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Simone Reppermund, PhD

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #4: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #4: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #4: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #1: (No Response)

Reviewer #2: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #4: Yes

**********

6. Review Comments to the Author

Reviewer #1: Title: In my opinion, the word ‘together’ should be deleted.

Abstract

Line 20 – the word ‘respectively’ should be deleted.

Line 81 – Note that there are multiple references showing them to be strongly related to each other. I suggest either deleting this sentence or adding some references to the contrary as well.

Line 145. I recommend deleting the word “indeed”

Line 147-149 There are multiple studies showing a significant relationship between social isolation and loneliness. Those should also be cited.

Line 553 – you still use the ‘lonely in a crowd’ term, which should be changed.

Line 562 - “support with every tasks” – a word seems to be missing

Line 615. The first conclusion is simply self-congratulatory and could be deleted. The other conclusions should convince the reader whether this analysis was worth while, without the author telling the reader that.

In general – I was not able to read all sections very carefully, yet I found some needs for editorial changes. I suggest the author consider having an editor review the manuscript carefully to detect any other editorial needs.

Reviewer #2: (No Response)

Reviewer #4: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Reviewer #4: No

PLoS One. 2020 Mar 23;15(3):e0230673. doi: 10.1371/journal.pone.0230673.r004

Author response to Decision Letter 1

4 Mar 2020

PONE-D-19-26452R1

Examining social isolation and loneliness together in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

PLOS ONE

Dear Dr. Menec,

==============================

Please proofread the manuscript very carefully and address the minor changes suggested by reviewer 1. Once these minor edits are corrected, the manuscript will be accepted for publication.

Dear Dr. Reppermund;

We have made the suggested edits and have also reviewed the paper for typos. See below for responses to the suggested edits.

Sincerely,

Verena Menec, PhD

RESPONSE: ==============================

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

Please include the following items when submitting your revised manuscript:

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• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

We look forward to receiving your revised manuscript.

Kind regards,

Simone Reppermund, PhD

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #4: All comments have been addressed

________________________________________

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #4: Yes

________________________________________

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #4: Yes

________________________________________

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #1: (No Response)

Reviewer #2: Yes

Reviewer #4: Yes

________________________________________

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #4: Yes

________________________________________

6. Review Comments to the Author

Reviewer #1: Title: In my opinion, the word ‘together’ should be deleted.

We have changed the wording to “in combination”

Abstract

Line 20 – the word ‘respectively’ should be deleted.

This change has been made.

Line 81 – Note that there are multiple references showing them to be strongly related to each other. I suggest either deleting this sentence or adding some references to the contrary as well.

We have edited the sentence to say that several studies show that social isolation and loneliness are only weakly correlated.

Line 145. I recommend deleting the word “indeed”

This change has been made.

Line 147-149 There are multiple studies showing a significant relationship between social isolation and loneliness. Those should also be cited.

The point in this section was not to discuss how social isolation and loneliness are related to each other, but rather how the interaction between the two variables is related to mortality. We have edited the sentence to make this clearer.

Line 553 – you still use the ‘lonely in a crowd’ term, which should be changed.

This change has been made.

Line 562 - “support with every tasks” – a word seems to be missing

This change has been made.

We have revised this sentence.

We have reviewed the paper for typos.

Reviewer #2: (No Response)

Reviewer #4: (No Response)

Attachment

Submitted filename: reviews 2.docx

Click here for additional data file.^{(17.9KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0230673.r005

Decision Letter 2

Simone Reppermund

6 Mar 2020

Examining social isolation and loneliness in combination in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

PONE-D-19-26452R2

Dear Dr. Menec,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication.

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With kind regards,

Simone Reppermund, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

PLoS One. doi: 10.1371/journal.pone.0230673.r006

Acceptance letter

Simone Reppermund

10 Mar 2020

PONE-D-19-26452R2

Examining social isolation and loneliness in combination in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

Dear Dr. Menec:

I am pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please notify them about your upcoming paper at this point, to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

For any other questions or concerns, please email plosone@plos.org.

Thank you for submitting your work to PLOS ONE.

With kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Simone Reppermund

Academic Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 Table. Adjusted analyses for middle-aged (age 45–64) versus older individuals (age 65–85).

(DOCX)

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S2 Table. Adjusted analyses for women versus men.

(DOCX)

Click here for additional data file.^{(16.5KB, docx)}

S1 Fig. Social isolation/loneliness groups by desire for more social participation and psychological distress.

(JPG)

Click here for additional data file.^{(55.4KB, jpg)}

Attachment

Submitted filename: Response to Reviewers.docx

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Attachment

Submitted filename: reviews 2.docx

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Data Availability Statement

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PERMALINK

Examining social isolation and loneliness in combination in relation to social support and psychological distress using Canadian Longitudinal Study of Aging (CLSA) data

Verena H Menec

Nancy E Newall

Corey S Mackenzie

Shahin Shooshtari

Scott Nowicki

Roles

Abstract

Background

Methods

Results

Conclusion

Introduction

Conceptualizing social isolation and loneliness

The health-related outcomes of social isolation and loneliness

Social isolation and loneliness groups

The present study

Methods

Data source

Study sample

Measures

Social isolation/loneliness groups

Desire for more social participation

Social support

Psychological distress

Covariates

Analytic approach

Results

Table 1. Sample description.

Table 2. Social isolation/loneliness groups by covariates and outcomes measures: Weighted percentages (within each group) or weighted means.

Fig 1. Social isolation/loneliness groups by social support.

Table 3. Comparisons of social isolation/loneliness groups for desire for more social participation.

Table 4. Comparisons of social isolation/loneliness groups for social support.

Table 5. Comparison of social isolation/loneliness groups for psychological distress.

Discussion

Limitations

Conclusions

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Decision Letter 0

Simone Reppermund

Roles

Author response to Decision Letter 0

Decision Letter 1

Simone Reppermund

Roles

Author response to Decision Letter 1

Decision Letter 2

Simone Reppermund

Roles

Acceptance letter

Simone Reppermund

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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