Dyadic effects of distress on sleep duration in advanced cancer patients and spouse caregivers

Abstract

Objective:

Short sleep duration is a common problem for both advanced cancer patients and their spouse caregivers. Sleep and distress have been shown to be interdependent in patient-caregiver and spouse dyads, yet virtually no work has explored the dyadic effects of psychological distress on sleep in advanced cancer patients and spouse caregivers. The goal of the present study was to examine the dyadic impact of anxiety and depression on sleep duration in a sample of advanced cancer patients and their spouse caregivers. It was hypothesized that, for both patients and caregivers, anxiety and depression in individuals would be associated with sleep duration in both themselves (actor effects) and in their spouses (partner effects).

Method:

Advanced cancer patients and their spouse caregivers (N = 87 dyads) completed cross-sectional questionnaires assessing demographic variables, subjective health, subjective sleep duration, and anxiety and depression symptoms.

Results:

Controlling for sex, age, and subjective health, individuals’ anxiety was negatively associated with their own and their partner’s sleep duration. No significant actor or partner effects were found for depression.

Conclusions:

Results provided partial support for hypotheses. Although past work has demonstrated links between subjective sleep disturbance and anxiety/psychological distress, this is one of the first studies to examine partner effects of distress on sleep disturbance in advanced cancer patients and spouse caregivers.

Background

Sleep disturbance—broadly defined as difficulty falling or staying asleep—is a highly prevalent and bothersome problem in individuals diagnosed with cancer.¹ Up to 75% of cancer patients report poor sleep, and research suggests that the prevalence of sleep problems is approximately two times higher in cancer patients compared with the general population.² Disturbed sleep in cancer patients has been associated with numerous negative mental and physical health outcomes, including anxiety and depressive symptoms, pain, and increased mortality.^{3, 4}

Sleep difficulties are similarly prevalent and harmful for family caregivers of cancer patients, particularly among caregivers of those with advanced cancer. It is estimated that over 95% of advanced cancer caregivers experience sleep disturbance.⁵ Poor sleep may contribute to difficulties actually executing daily caregiving tasks and to increased caregiver burden.^{2, 6, 7} It has also been linked to anxiety, depression and worse physical health in caregivers, as well as interference with the grieving process and difficulty returning to pre-caregiving responsibilities after the patient’s death.^{5, 7–9}

Sleep Duration

Short sleep duration is one of the most commonly-reported forms of sleep disturbance among cancer caregivers,¹⁰ and previous work has demonstrated that both cancer patients and caregivers report getting less than the recommended minimum amount of sleep per night.^{3, 6, 11, 12} Subjective sleep duration is directly associated with meaningful clinical outcomes, including many physical health conditions,^{3, 13, 14} all-cause and cancer-specific mortality,^{14, 15} as well as survival in advanced cancer patients.³ Importantly, sleep duration is also associated with various mental health conditions, including anxiety and depression.^{13, 16, 17} While anxiety is associated with shorter sleep duration (e.g.,¹⁸), depression—along with some negative physical outcomes like mortality—is associated with both short and long sleep duration^{3, 14, 16} (generally defined as < 7 hours and > 9 hours per night, respectively^{11, 14}). Past work suggests that the relationship between anxiety/depression and sleep disturbance in general is bidirectional,¹⁹ although much less work has examined the direction of the relationship between anxiety/depression and sleep duration specifically.

Sleep duration is also significantly correlated with other elements of sleep disturbance, including wake time after sleep onset and sleep efficiency, and with validated measures of overall sleep disturbance.²⁰ However, sleep duration, independent of insomnia more broadly, has been found to predict the course of depressive and anxiety disorders,¹⁷ suggesting that sleep duration may provide unique information above and beyond more global measures of sleep disturbance.

Sleep in a Dyadic Context

Sleep is often conceptualized on an individual level; however, most adults share a bed, and often a regular nighttime routine, with a significant other.²¹ Thus, the effect that spouses or partners have on each other’s sleep may be particularly strong, though few studies (e.g.,²²) have systematically investigated sleep on a dyadic level. Interdependence theory²³ suggests that individuals that are part of the same social system—such as spouses/partners, or patients and caregivers—influence one another. This pattern has been observed in the existing literature and in large nationally-representative sleep surveys. For example, 26% of cohabiting adults report that their own sleep suffers due to sleep disturbance in their partner, and 23% of cohabiting couples sleep in separate beds or bedrooms due to one partner’s sleep problems.²¹ There is reason to believe that the patterns of interrelated sleep problems observed in the general population exist in the cancer population as well.²⁴

Importantly, an individual’s sleep may be impacted not only by a partner’s sleep, but also by a partner’s psychological well-being. Distress and sleep disturbance have been found to be highly interdependent in spouses.^{24, 25} Specifically, among healthy heterosexual couples, anxiety and depression symptoms in husbands predict lower sleep duration and poorer mental health for wives a year later, and anxiety in wives predicts lower sleep duration in husbands a year later.²⁵ In a review of the literature, Troxel et al.²² noted a “small but consistent literature” (p. 397) suggesting an association between relationship quality and sleep quality. When a cancer patient and caregiver both experience disturbed sleep, this may exacerbate its deleterious effects, leading to worsened relationship quality and impaired dyadic coping.²⁶

Current Study

Most research on sleep disturbance in cancer caregivers has focused on early-stage disease.²⁷ However, the biological and psychological processes influencing sleep in cancer patients may be exacerbated in the context of advanced cancer. For example, advanced cancer patients often undergo more arduous treatments or have more pain than earlier-stage patients, both of which can impact sleep.¹⁸ Similarly, advanced cancer patients may experience greater psychological distress, which has also been shown to result in worse sleep disturbance (e.g.,^{4, 18}). Additionally, caregivers of advanced cancer patients have demonstrated higher rates of sleep disturbance than caregivers of earlier-stage patients.¹⁰ These differences may limit generalizability of previous findings related to sleep in early-stage cancer. Adequate sleep is an important contributor to maintaining quality of life (e.g.,⁹), a priority for many patients with advanced cancer and their caregivers. Thus, identifying and managing sleep disturbance should be an important part of advanced cancer care; yet, sleep problems are often unaddressed by clinicians.²⁸

As noted above, disturbed sleep is a pervasive problem among advanced cancer patients and their caregivers. Patients and caregivers can substantially impact each other’s sleep; yet, little research has examined sleep in this dyadic context. Even less work has examined the dyadic effects of psychological distress on sleep in patients and caregivers, particularly in the setting of advanced cancer.²⁷ To address this gap in knowledge, this study sought to determine how psychological distress impacts sleep in a sample of advanced cancer patients and their spouse caregivers.

Specifically, it was hypothesized that increased anxiety would predict greater sleep disturbance for both patients and caregivers. It was expected that depression would exhibit a non-linear relationship with sleep disturbance, such that both high and low levels of depression would be associated with greater sleep disturbance for both patients and caregivers.

Consistent with interdependence theory, it was also hypothesized that increased anxiety would also predict increased sleep disturbance in one’s spouse. It was expected that depression would also exhibit a non-linear relationship with sleep disturbance in one’s spouse, such that both high and low levels of depression in the patient would predict greater sleep disturbance in the caregiver, and both high and low levels of depression in the caregiver would be associated with greater sleep disturbance in the patient.

Methods

The present study is a secondary analysis of data that were gathered as part of a larger observational study of advanced cancer patient and spouse caregiver couples; a more detailed description of recruitment and study procedures can be found in Reblin, Sutton, et al.,²⁹ and Reblin, Heyman, et al.³⁰

Participants

Participants were recruited from outpatient thoracic and gastro-intestinal clinics at a National Cancer Institute-designated Comprehensive Cancer Center. Patient inclusion criteria included a diagnosis of stage III or IV non-small cell lung, colorectal, pancreatic, esophageal, gastric, gallbladder, hepatocellular, or bile duct cancer; Eastern Cooperative Oncology Group performance status score of 0–2 or Karnofsky Performance Status scores of at least 70; a life expectancy of at least six months; undergoing active cancer treatment (i.e., chemotherapy, immunotherapy, or radiation therapy); and no current severe anxiety or depression documented in the patient’s electronic medical record. Patients were required to have a cohabiting spouse or partner who reported providing at least some care to the patient and who also agreed to participate in this study. Both patients and caregivers were required to be at least 18 years old and able to communicate in English.

Procedure

All study procedures were conducted in accordance with ethical guidelines and were approved by an Institutional Review Board (Chesapeake IRB #MCC18495). As part of the larger study, consenting patient and caregiver participants each completed a battery of self-report questionnaires. Questionnaires assessed demographic variables, including age, gender, and race/ethnicity. Participants each also reported on their subjective health, which was assessed with a single item (“How would you describe your overall health?”); participants responded on a 5-point Likert-type scale ranging from 1 (“Excellent”) to 5 (“Very Poor”). Sleep disturbance was operationalized as subjective sleep duration, which was assessed with a single item: “How many hours of sleep did you receive last night?”.

The Hospital Anxiety and Depression Scale (HADS)³¹ was used to assess anxiety and depression symptoms. The HADS is a widely-used 14-item measure comprised of a 7-item anxiety subscale (HADS-A) and a 7-item depression subscale (HADS-D). Responses are given on a 4-point Likert-type scale ranging from 0 to 3. Total scores for each subscale range from 0 to 21, with higher scores indicative of more severe symptoms. A score of 8 or above on either subscale is suggestive of clinically-significant levels of anxiety or depression.³²

Data Analysis

As noted earlier, distress and sleep have been shown to be highly interdependent in spouses and patient-caregiver dyads.^{24, 25} The actor-partner interdependence model posits that the measurements of paired individuals, such as spouses, tend to be correlated.³³ When a person’s behaviors or experiences predict an outcome in his- or herself, this is termed an actor effect; when a person’s behaviors or experiences predict an outcome in his or her partner, this is called a partner effect.³³ Thus, an actor-partner interdependence model was used in which patient and caregiver sleep duration were simultaneously regressed on their own anxiety and depression (actor effects), and on their partner’s anxiety and depression (partner effects). To test for a curvilinear relationship between depression and sleep duration, as suggested by Zhai and colleagues,¹⁶ two quadratic terms (representing the squared effects of patient depression and caregiver depression) were entered into the model as predictor variables. Sex, age, and general health were also entered into the model as control variables. See Figure 1 for a simplified depiction of this model. Maximum likelihood estimation was used to handle missing data, allowing use of all available data in the model and producing unbiased parameter estimates under the missing-at-random assumption.³⁴

Figure 1.

Simplified path model depicting effects of anxiety and depression on sleep duration. Note: *p < .05, ***p < .001. ^a-f Effects were constrained to be equal across patients and caregivers. Significant effects are depicted with bolded, solid lines; dotted lines represent nonsignificant effects. Although not displayed here, patient sex, age, and general health, and caregiver age and general health were also entered into the model as covariates.

To increase parsimony and power of the final model,³⁵ parameter estimates for key effects (i.e., actor and partner effects of anxiety and depression on sleep duration) were constrained to be equal across patients and caregivers as they were observed to be of similar direction and magnitude. The fit of the constrained model was not significantly different from the unconstrained model (Δχ² = 1.742, df = 6, p = .942), suggesting that these constraints were acceptable and consistent with the data; thus, results of the constrained model are reported here. The final constrained model also demonstrated excellent absolute fit:³⁶ χ²(8) = 1.94, p = .983; CFI = 1.00; RMSEA = 0.00, 90% CI = 0.00, 0.00. All analyses were conducted using Mplus 7.³⁷

Results

Sample characteristics and descriptive statistics

See Table 1 for sample characteristics and descriptive statistics. A total of 87 patient-caregiver dyads (N = 174 paired individuals) were included in analyses; all dyads were heterosexual couples. Patients reported sleeping 7.19 hours the previous night (range = 3.00 – 12.00) and caregivers reported sleeping 6.71 hours (range = 1.50 – 9.00). Although patients reported significantly more hours of sleep than caregivers (t = 2.36, p = .020), patient and caregiver sleep duration were significantly correlated (r = .23, p = .030). Patients and caregivers reported average anxiety and depression levels below the established clinical cutoff scores on the HADS-A and HADS-D. Caregivers reported significantly more anxiety than patients (t = −5.05, p < .001), but depression did not differ between patients and caregivers (t = −0.20, p =.846).

Table 1.

Sample characteristics and descriptive statistics (N = 87 dyads; 174 individuals).

Variable		N (%) or M(SD)
		Patient (n = 87)	Caregiver (n = 87)
Sex	Male	62 (71.3%)	25 (28.7%)
	Female	25 (28.7%)	62 (71.3%)
Race	White/Caucasian	81 (93.1%)	78 (89.7%)
	Black/African-American	5 (5.7%)	4 (4.6%)
	American Indian/Alaska Native	1 (1.1%)	2 (2.3%)
	Other	0 (0.0%)	1 (1.1%)
	Missing	0 (0.0%)	2 (2.3%)
Ethnicity	Hispanic	3 (3.4%)	5 (5.7%)
	Non-Hispanic	84 (96.6%)	80 (92.0%)
	Missing	0 (0.0%)	2 (2.3%)
Education level	Less than high school	3 (3.4%)	2 (2.3%)
	High school graduate/equivalent	13 (14.9%	14 (16.1%)
	Some college or vocational school	28 (32.2%)	31 (35.6%)
	College graduate (4 years)	16 (18.4%)	13 (14.9%)
	Some graduate/professional school	7 (8.0%)	6 (6.9%)
	Graduate or professional degree	20 (23.0%)	21 (24.1%)
Employment status	Unemployed	66 (75.9%)	52 (59.8%)
	Part-time employment	5 (5.7%)	11 (12.6%)
	Full-time employment	15 (17.2%)	21 (24.1%)
	Missing	1 (1.1%)	3 (3.4%)
Annual household income (patient report)	$10,000 – $24,999	5 (5.7%)
	$25,000 – $39,999	13 (14.9%)
	$40,000 – $49,999	8 (9.2%)
	$50,000 – $74,999	26 (29.9%)
	$75,000 or more	33 (37.9%)
	Missing	2 (2.3%)
Relationship status (patient report)	Married	86 (98.9%)
	Living as married	1 (1.1%)
Relationship length (years) (patient report)		34.00 (15.61)
Age (years)		66.75 (9.28)	64.68 (9.24)
Sleep last night (hours)		7.19 (1.68)	6.71 (1.30)
HADS-Anxiety score		5.13 (3.52)	7.82 (4.31)
HADS-Depression score		4.70 (3.08)	4.78 (3.68)
Overall health score		2.84 (0.95)	2.29 (0.75)

Effects of anxiety and depression on sleep duration

Model results are displayed in Figure 1. Both actor effects (i.e., an individual’s distress impacting his/her own sleep) and partner effects (i.e., an individual’s distress impacting his/her partner’s sleep) were examined. With regard to actor effects, an individual’s anxiety was negatively associated with his/her own sleep duration (B = −.14, p < .001, 95% CI = −0.20, −0.07), controlling for sex, age, and general health. This indicates that each one-unit increase in anxiety was associated with 0.14 fewer hours of sleep (8.4 minutes). Depression did not exhibit significant linear (B = 0.14, p = .137, 95% CI = −0.05, 0.34) or quadratic associations (B = −0.01, p = .392, 95% CI = −0.02, 0.01) with an individual’s own sleep duration.

With regard to partner effects, there was a significant association between an individual’s anxiety and his/her partner’s sleep duration (B = −0.07, p = .046, 95% CI = −0.14, −0.001), controlling for sex, age, and general health; each one-unit increase in one person’s anxiety was associated with 0.07 fewer hours of sleep (4.2 minutes) for his/her partner. No significant partner effects were found for depression (linear: B = −0.12, p = .272, 95% CI = −0.32, 0.09; quadratic: B = 0.02, p = .062, 95% CI = −0.001, 0.03).

Conclusions

Sleep disturbance is a common and distressing problem for both advanced cancer patients and their spouse caregivers.¹ Poor sleep has been associated with increased symptoms and mortality in cancer patients,^{1, 3} and may lead to health issues and impaired ability to provide care in caregivers.¹² Although several studies have demonstrated links between subjective sleep disturbance and anxiety or psychological distress, this is one of the first studies to examine partner effects of anxiety and depression on sleep duration in advanced cancer patients and spouse caregivers. Although this study focused specifically on one element of sleep disturbance—sleep duration—the actor effects of anxiety observed in the present study are generally consistent with the small existing body of research on sleep disturbance more broadly. For instance, Gibbins and colleagues⁹ found significant associations between subjectively poor sleep and anxiety in advanced cancer patients as well as their family caregivers (though average sleep duration in their sample was approximately eight hours per night). Others (e.g.,⁴) have also demonstrated a link between anxiety symptoms and poor sleep in advanced cancer patients. The fact that the present study did not find significant effects of depression on sleep duration was unexpected and warrants additional investigation. It is possible that this pattern of findings was due to the more limited range and variability in depression symptoms (compared to anxiety symptoms) in the present sample.

Of note, patients reported significantly more hours of sleep than caregivers (7.19 hours vs. 6.71 hours) and, on average, caregivers fell below the recommended minimum of 7 hours of sleep per night for healthy adults.¹¹ This short sleep duration is generally consistent with previous work investigating sleep duration in cancer caregivers (e.g.,^{6, 12}), although other work has found that advanced cancer patients also report short sleep duration (e.g.,³). Carney and colleagues³⁸ found that patients and caregivers did not differ significantly with regard to total sleep time; however, this study excluded patients with metastatic disease, and sleep was measured objectively. Interestingly, as most patients were men and most caregivers were women, the finding that patients reported more sleep than caregivers may reflect conclusions in the broader literature on gender differences in sleep that insomnia and short sleep duration are more prevalent in women.³⁹

Study Limitations

Results should be interpreted in the context of several limitations. This was a cross-sectional study, so direction and causality of these effects cannot be inferred. For example, it is possible that decreased sleep duration caused increases in anxiety or that the relationship between sleep duration and anxiety is bidirectional. As noted above, this study excluded participants with severe anxiety or depression documented in their medical records, which limits generalizability of these findings to those with low to moderate levels of anxiety or depression.

This was also a secondary analysis; as such, some informative data was unavailable. Most importantly, although all participant dyads were married or living as married, data were not collected on whether these dyads shared a bed/bedroom. About a quarter of couples sleep in separate beds or bedrooms,²¹ so it is probable that some portion of the dyads in the present study did not share a bed, and therefore had a smaller influence on each other’s sleep; this could have diminished our ability to detect partner effects. The inability to assess whether participating dyads slept in the same bed/bedroom is a noteworthy weakness that limits the interpretation of findings regarding the extent to which partners influence each other’s sleep. Patient clinical information was also not collected, so factors that may be related to both sleep and distress, such as stage or specific diagnosis, time since diagnosis, or treatment history, could not be considered in analyses.

Further, this study focused on self-reported sleep duration as an indicator of sleep disturbance. However, sleep duration is only one aspect of sleep disturbance. Although sleep duration is one of the most common issues in cancer caregivers,¹⁰ there are several other potentially-important indicators of poor sleep that were not assessed in the present study, such as sleep efficiency or daytime functioning. Sleep duration was also captured by a single self-report item in the present study. However, self-report is a widely-used method of assessing sleep duration, and self-reported sleep duration is moderately correlated with objectively-measured sleep duration.⁴⁰ Even when assessed via a single item, self-reported sleep duration has been directly associated with numerous chronic mental and physical health conditions.^{13, 14} Additionally, the item used in the present study substantially reduced retrospection and mental calculation by focusing only on the preceding night, and therefore may have minimized recall bias. Nonetheless, future studies should incorporate validated sleep instruments and objective measurements to triangulate sleep duration and quality (e.g., actigraphy, polysomnography).

Clinical Implications

The observed associations between anxiety and sleep duration underscore the importance of providers routinely monitoring for both psychological distress and sleep disturbance. The finding that caregivers reported significantly more anxiety than patients, as well as the observed partner effects of anxiety, have potentially-important implications for the development of interventions for advanced cancer dyads. For example, many oncology clinics routinely screen patients for psychological distress and offer support services; it may be prudent for these existing screening and support services to be extended to spouse caregivers to address their own psychological distress.

These findings strongly support further research of the dyadic effects of distress on sleep to identify longitudinal effects on holistic sleep outcomes for those coping with advanced cancer and their caregivers. Despite numerous interventions targeting sleep disturbance in cancer patients, a significant portion of advanced cancer patients and caregivers still report poor sleep.^{3, 6, 12} To maximize effectiveness, interventions for sleep disturbance in cancer patients or caregivers may benefit from including strategies for coping with a partner’s anxiety, or including both members of the couple. Both sleep and emotional health are important factors in healing, cancer recurrence, health care costs, the ability to provide safe and effective caregiving, as well as relationship functioning.^{1, 22} Findings of the present study and others suggest that sleep and psychological health are part of an interdependent system, both within an individual but also within a couple. As such, addressing only one area may not be sufficient to ensure the optimal health and well-being of advanced cancer patients and their spouse caregivers.