Abstract
[Purpose] We aimed to determine the relationships between social frailty, physical function, nutritional status, and appetite among community-dwelling older adults. [Participants and Methods] Women aged ≥65 years (n=45) who attended a day-care service in City A, Tokushima Prefecture, between August and September 2024, were included. Data concerning baseline characteristics, body composition analyzer, physical function (grip strength, walking speed), nutritional status, and appetite were collected. Social frailty was classified into robust, pre-frail, and frail groups using Yamada’s questionnaire. Statistical analyses were performed using ANOVA and a Kruskal–Wallis test. [Results] The participants comprised 5 robust, 15 pre-frail, and 25 frail women. Significant differences were observed among the three groups in terms of muscle mass, number of cohabitants, phase angle, and number of medications. Those with poor appetite had a significantly lower skeletal muscle mass index, and appetite loss was more frequent among those living with cohabitants. [Conclusion] Social frailty was associated with reduced muscle mass and fewer cohabitants. Individuals living alone tended to report better appetite status; however, they also exhibited a lower skeletal muscle mass index. These associations should be interpreted with caution given the limited sample and study design.
Key words: Social frailty, Appetite, Cohabitation status
INTRODUCTION
Japan is currently experiencing a rapid decline in birth rate and population aging. According to the Annual Report on the Aging Society (June 2024), as of October 1, 2023, the national aging rate reached 29.1%, indicating that Japan has entered a super-aged society1). Tokushima Prefecture has the third-highest proportion of adults aged ≥65 years (35.9%) in Japan, following Akita and Kochi Prefectures. In depopulated rural areas distant from the city center, the proportion exceeds 50%, demonstrating the severity of aging in regional communities2, 3). Moreover, the proportion of older adults living alone is increasing, reaching 15.0% among men and 22.1% among women in 20204). In areas with a high aging rate, the prevalence of older adults living alone or in “older adult-to-older adult” caregiving households is particularly high, making the extension of healthy life expectancy a critical public health goal.
With aging, the prevalence and severity of chronic diseases increase, resulting in growing numbers of patients with health-related issues. Therefore, early detection, intervention, prevention, and continuous support have become essential health strategies. Nationwide efforts have been initiated to promote health and prevent long-term care dependency. In Tokushima Prefecture, with the progress of depopulation, even the very elderly are becoming independent and relying primarily on automobiles and other means of transportation. Among facility residents, social frailty is rare, and sarcopenia and physical functional impairment are more common. In the case of day care centers, it is highly likely that users with robust and frail social frailty are mixed. Therefore, this study focused on day care centers to understand the onset of social frailty.
Frailty is considered an intermediate state between robust health and disability5). It is a multidimensional condition comprising three domains: physical frailty, social frailty, and psychological frailty. The presence of any of these components is associated with sarcopenia, with particularly strong correlations observed between physical frailty and sarcopenia6, 7).
Previous studies have primarily focused on muscle mass and physical function related to sarcopenia and physical frailty. Although many studies have investigated physical frailty, social frailty is considered to be involved in an earlier stage preceding physical frailty. However, social frailty remains insufficiently understood because it is influenced by multiple factors. In recent years, research on social frailty has increased, and several studies have examined relationships between home environment and frailty-related outcomes. Among studies that have investigated the relationships among social frailty, home environment, and dietary habits, Kobayashi et al. reported that social frailty was significantly associated with malnutrition8).
Regarding eating behavior, previous studies have reported that older adults who primarily eat alone owing to mobility difficulties or being bedridden—regardless of cohabitation status—exhibit lower dietary diversity and have approximately twice the prevalence of frailty and depression compared with those who share meals with others9,10,11). Therefore, it is important to examine the relationships between social frailty, nutritional status, and appetite, and to explore potential approaches to improve these factors. Nevertheless, few studies have investigated the associations among social frailty, nutrition, and appetite, or the influence of living arrangements on dietary behavior. Therefore, this study aimed to clarify the relationships between social frailty, physical function, nutritional status, and appetite among community-dwelling older women attending day-care services.
PARTICIPANTS AND METHODS
This cross-sectional study was conducted between August and September 2024 at a day-care service center located in City A, Tokushima Prefecture, Japan. In total, 59 community-dwelling older adults aged ≥65 years (5 men, 54 women) who provided written informed consent were recruited. Because body composition measurement required participants to maintain a standing position, individuals who were unable to stand safely and steadily were excluded. In addition, nutritional status, physical and social frailty were assessed using questionnaires, individuals with cognitive decline that could hinder accurate evaluation were also excluded, as were those with incomplete responses or missing measurement data. After these exclusions, 48 participants (3 men and 45 women) were included in the initial analysis. Because only three men remained after data screening, male participants were excluded, and the final analysis was conducted on 45 women (Fig. 1).
Fig. 1.
Participant selection.
We collected data concerning age, sex, height, weight, body mass index (BMI), medical history, and medication types. Body composition was measured using a multifrequency bioelectrical impedance analyzer (MC-780A-N, TANITA Corp., Tokyo, Japan). Before measurement, the participants’ palms and soles were moistened with electrolyte sheets. After measuring body weight, the participants held the analyzer grips and maintained an upright position for approximately 15 s. The following data were recorded: basal metabolic rate, body fat percentage, fat mass, muscle mass, skeletal muscle mass index (SMI), total body water, protein mass, and phase angle (PhA). Based on previous research, PhA data from the left side of the body at 50 Hz were used12).
Physical frailty was assessed using the revised Japanese version of the Cardiovascular Health Study (J-CHS) criteria. Social frailty was evaluated using a questionnaire developed by Yamada and Arai13), which consisted of four items assessing: (1) social resources, (2) basic social activities, (3) social participation, and (4) general resources. The participants were categorized into robust (0 items), social pre-frailty (1 item), or social frailty (2–4 items) groups. In addition, living arrangements (living alone or cohabiting) and the number of household members were recorded.
Physical performance was evaluated using grip strength and walking speed. Grip strength was measured using a hand dynamometer (Takei Scientific Instruments Co., Ltd., Niigata, Japan), and the maximum value between the right and left hands was used. Walking ability was assessed using the fastest 5 m walking speed.
Nutritional status was assessed using the Mini Nutritional Assessment Short-Form (MNA®-SF), with scores <12 points classified as at risk of malnutrition. Appetite was assessed using the Simplified Nutritional Appetite Questionnaire for Japanese Elderly (SNAQ-JE), and scores <15 points indicated appetite loss.
All statistical analyses were performed using R Commander version 4.3.2. Participants were categorized into three groups—robust, social pre-frailty, and social frailty—based on Yamada’s social frailty questionnaire. The Shapiro–Wilk test was used to assess data normality. Depending on the distribution, one-way analysis of variance (ANOVA) or the Kruskal–Wallis test was used to determine the differences of three groups of social frailty. In addition, participants were divided into two groups according to appetite status (normal appetite vs. appetite loss), and comparisons were made using the two-sample t-test or Mann–Whitney U test after checking for normality. Values with normal distribution are shown as mean ± standard deviation (mean ± SD) and those without normal distribution are shown as median ± interquartile range (median [IQR]). A p-value of 0.05 was considered statistically significant. As post-hoc tests to determine the size effects of physical and nutritional characteristics to social frailty groups and to appetite status, we applied either Turkey’s test, Steel–Dwass test, or Games–Howell test depending on their distributions and variances. Effect size to three groups were reported as eta square (ŋ 2) or Cohen’s f, and those to appetite status were reported as r.
This study was approved by the Ethics Committee of Tokushima Bunri University (Approval No. R6-2). The participants were provided with a written explanation of the study at the research site, and only those who provided written informed consent were included. The participants were informed that they could withdraw from the study at any time, and in cases of withdrawal, data were discarded according to the written withdrawal statement and ethical procedures.
RESULTS
We investigated factors related to appetite, nutrition, and physical aspects in community-dwelling older adults according to the presence or absence of social frailty. Based on Yamada’s social frailty questionnaire, 5 (11.1%) participants were classified as robust, 15 (33.3%) with social pre-frailty, and 25 (55.6%) with social frailty.
The participants’ basic characteristics according to frailty status are shown in Table 1. No significant differences were observed among the three groups in terms of basic attributes.
Table 1. Basic characteristics.
| Category | Robust (n=5) | Pre-frail (n=15) | Frail (n=25) |
| Height (cm) | 154.0 ± 4.97 | 148.3 ± 6.51 | 147.0 ± 4.58 |
| Weight (kg) | 55.2 ± 9.5 | 50.9 ± 8.34 | 51.3 ± 10.15 |
| Body mass index (kg/m2) | 23.4 ± 4.76 | 23.0 ± 2.92 | 23.6 ± 3.93 |
| Age (years) | 82.4 ± 5.9 | 83.7 ± 6.96 | 85.0 ± 4.13 |
Women, n=45. Data are presented as mean ± SD for normally distributed variables.
Comparisons of body composition and related factors among the three social frailty groups are presented in Table 2. Significant differences were observed in muscle mass (p<0.01) and the number of cohabitants (p<0.05) between the robust and social frailty groups. In addition, phase angle (PhA) (p<0.01) and the number of medications (p<0.05) differed significantly between the social pre-frailty and social frailty groups. Effect size to three groups in social frailty in muscle mass is 0.088, while that in phase angle is 0.221. These results suggested that phase angle is more closely related to social frailty than muscle mass. However, no significant differences were observed in nutritional status or appetite among the three groups.
Table 2. Comparison of physical and nutritional characteristics among the groups.
| Category | Robust (n=5) | Pre-Frail (n=15) | Frail (n=25) | p-value | Effect size |
| Grip strength (kg) | 18.2 ± 4.11 | 15.9 ± 3.53 | 14.8 ± 3.7 | f=0.306 | |
| Muscle mass (kg) | 34.1 ± 1.37** | 32.2 ± 3.48 | 30.9 ± 2.02** | ##, ** | η2=0.088 |
| Skeletal muscle mass index (kg/m2) | 6.44 ± 0.57 | 6.37 ± 0.68 | 5.95 ± 0.46 | ## | f=0.413 |
| Phase angle (°) | 3.9 [3.7–4.2] | 4.3 [4.2–4.8]** | 3.9 [3.6–4.1]** | ##, ** | η2=0.221 |
| 5-m walk time (s) | 5.5 [4.8–5.8] | 6.2 [5.45–7.45] | 6.4 [5.4–8.8] | η2=0.037 | |
| Care level | 2 [2–2] | 1 [1–2] | 2 [2–2] | η2=0.128 | |
| Revised Japanese version of the Cardiovascular Health Study (points) | 2 [2–3] | 2 [1–4] | 3 [2–3] | η2=0.013 | |
| Basal metabolic rate (kcal) | 1,039 [992–1,088] | 945 [898–1,065.5] | 962 [880–1,019] | η2=0.088 | |
| Number of medication types (kinds) | 5 [3–6] | 3 [2–5]* | 5 [4–8]* | #, * | η2=0.200 |
| Number of cohabitants (persons) | 3 [3–3]* | 2 [1–3] | 0 [0–2]* | #, * | η2=0.170 |
| Mini Nutritional Assessment Short-Form (points) | 11 [11–12] | 12 [10.5–13.5] | 12 [10–13] | η2=0.004 | |
| Simplified Nutritional Appetite Questionnaire for Japanese Elderly (points) | 13 [12–13] | 15 [13–15.5] | 15 [11–15] | η2=0.024 |
Mean ± SD, median [IQR]. Data are presented as mean ± SD for normally distributed variables and median [IQR] for non-normally distributed variables. #p<0.05, ##p<0.01 (ANOVA / Kuruskal–Wallis test); *p<0.05, **p<0.01 (post-hoc tests: Tukey’s test, Steele–Dwass test, Games–Howell test). Care level (Support Level 1–2=scores 1–2; Care Level 1–5=scores 3–7).
A comparison between participants with and without appetite loss is shown in Table 3. Those with appetite loss had significantly lower SMI values and a greater number of cohabitants (p<0.05).
Table 3. Comparison between groups with and without loss of appetite.
| Category | No abnormality (n=22) | Loss of appetite (n=23) | Effect size |
| Body mass index (kg/m2) | 23.8 ± 2.76 | 23.0 ± 4.35 | r=0.105 |
| Phase angle (°) | 4.30 ± 0.81 | 4.06 ± 0.52 | r=0.176 |
| Skeletal muscle mass index (kg/m2) | 6.33 ± 0.82* | 5.96 ± 0.32* | r=0.373 |
| Basal metabolic rate (kcal) | 971.5 [894–1071.5] | 956.0 [901–1039.0] | r=0.066 |
| Care level | 1.5 [1–2] | 2.0 [2–2] | r=0.268 |
| Grip strength (kg) | 15.8 ± 3.96 | 15.2 ± 3.62 | r=0.087 |
| 5-m walk time (s) | 6.35 [4.85–8.67] | 5.80 [5.45–6.95] | r=0.020 |
| Mini nutritional assessment short-form (points) | 12.13 ± 1.52 | 11.39 ± 1.94 | r=0.212 |
| Number of medication types (kinds) | 5 [3.25–6.0] | 5 [3.00–6.5] | r=0.058 |
| Number of cohabitants (persons) | 0 [0–2]* | 2 [2–3]* | r=0.311 |
Data are presented as mean ± SD for normally distributed variables and median [IQR] for non-normally distributed variables. *p<0.05 (two-sample tests or Mann–Whitney U tests). Care level (Support Level 1–2=scores 1–2; Care Level 1–5=scores 3–7).
DISCUSSION
This study aimed to determine the relationships between social frailty, appetite, nutritional status, and physical factors among community-dwelling older adults using day-care services. No significant differences were observed in basic characteristics among the three social frailty groups. The mean BMI in all groups was approximately 23 kg/m2, close to the normal range, which may explain the absence of significant nutritional differences.
We obtained data concerning the number of participants living alone; however, the number of participants who engaged in solitary eating among cohabitants was not assessed. Therefore, it is difficult to determine whether the significant differences in cohabitation and appetite observed in this study were solely a result of living alone. Moreover, environmental factors such as terrain, distance to nearby supermarkets, and mobility status, which could influence appetite and nutritional condition, were not evaluated in detail.
Regarding comparisons among the three frailty groups, muscle mass was significantly lower in the social frailty group than in the robust group, and the proportion of participants living alone was higher. Older adults living alone tend to have poorer physical function compared with those living with others14). Similarly, in this study, both muscle mass and PhA were significantly lower in the social frailty group, suggesting that the quantity and quality of muscle may be related to social frailty.
PhA was significantly lower in the social frailty group compared with the pre-frailty group. PhA reflects the integrity and function of muscle cell membranes. Akamatsu et al.15) reported that age (negative association), SMI, and muscle quality (positive association) were independently related to PhA, indicating that PhA reflects muscle quality. The European Working Group on Sarcopenia in Older People 2 recently included muscle quality as an essential diagnostic factor, highlighting its growing importance16). The significantly lower PhA observed in the social frailty group in this study suggests that individuals with social frailty may have a higher risk of concurrent sarcopenia.
PhA is also known as an indicator of nutritional status. A low PhA has been associated with a higher risk of malnutrition, prolonged hospital stay, and increased mortality, and it is considered a stronger prognostic factor for survival than conventional anthropometric or biochemical nutritional indices17,18,19). Therefore, even when malnutrition is not detected using screening tools such as the MNA®-SF, PhA measurement may serve as a comprehensive assessment tool reflecting muscle quality, nutrition, and prognosis. In the present study, no significant difference in the PhA was observed between the frail and robust groups. This may be attributable to the small sample size of the robust group (n=5), which likely resulted in a substantial imbalance compared to the other two groups. Additionally, given the regional characteristics, including mountainous residential areas, some participants may have been managing their daily lives with minimal support and socially inclined to use day-care services. These contextual factors may have contributed to the relatively high prevalence of social frailty among individuals attending day-care facilities.
The number of medications was significantly higher in the social frailty group compared with the pre-frailty group, indicating a tendency toward polypharmacy. The risk of drug-related adverse events is known to increase when older adults take ≥6 medications, and approximately 25% of those aged ≥75 years use ≥7 medications20, 21). While multiple comorbidities may necessitate polypharmacy, collaboration among healthcare professionals and preventive physiotherapy should be encouraged to avoid unnecessary medication use.
In the comparison according to appetite status, the SNAQ-JE was used as an assessment tool for appetite loss in older adults. Shimizu et al. reported that the SNAQ-JE accurately identified the severity of malnutrition defined using the GLIM criteria and sarcopenia among hospitalized older adults22). In this study, SMI was significantly lower among those with appetite loss, and the participants with more cohabitants showed a higher prevalence of appetite loss.
Solitary eating is known to be associated with depression, appetite loss, and malnutrition9, 23, 24). However, in this study, participants with social frailty did not show significant differences in appetite or nutrient status. It is possible that individuals living alone may maintain appetite by freely choosing and consuming their preferred foods. Nevertheless, even among those with more cohabitants, individuals who frequently ate alone have been reported to have a 1.4-fold higher risk of malnutrition, greater depressive tendencies, lower dietary diversity, and a lower BMI25). Therefore, cohabitation status alone may not directly affect appetite or nutrition, and future studies should include both the frequency and proportion of solitary eating.
The finding that SMI was significantly lower among those with appetite loss aligns with prior reports showing that appetite loss is associated with reduced muscle mass, muscle strength, activities of daily living, and cognitive function, as well as poor oral health26). Furthermore, the combined presence of appetite loss and masticatory dysfunction increases the risk of sarcopenia approximately 4.4-fold compared with either condition alone27). In this study, the participants with appetite loss exhibited a lower SMI even when living with others, suggesting that reduced muscle mass may accompany appetite decline regardless of living arrangements. Solitary living may help preserve appetite through self-determined food choices, but such freedom of intake may not guarantee adequate nutrient balance, potentially resulting in decreased muscle mass and quality, as reflected in lower SMI values.
Overall, our findings indicated that individuals living alone were more likely to experience social frailty. However, participants with a poor appetite were significantly more likely to have two or more cohabitants. In the present study, we did not assess factors such as whether cohabitants were absent during the daytime or whether meals were shared; therefore, we could not determine whether a solitary eating situation occurred despite living with others. Consequently, future research should include a detailed assessment of daytime living environments for a more comprehensive analysis. As of 2020, 35.2% of household heads aged ≥65 years in Japan live in single-person households, reflecting a growing trend of older adults living alone28). Therefore, preventive strategies for social frailty and appetite loss among single-living older adults should be further explored. Moreover, since detailed data on physical activity levels and nutrient intake were not collected in this study, future research should include additional assessments using activity and dietary questionnaires.
Finally, this study included only women, as men were excluded from the analysis. Among the individuals screened, only five were men, and only three agreed to participate; thus, the small number made it impossible to conduct a meaningful sex-specific analysis. Moreover, the number of male day-service users in the surveyed area was originally low, making adequate recruitment difficult. In future research, we aim to collaborate with additional day-service centers as well as more active community salons to increase the number of male participants and the overall sample size. This would allow for a larger robust group and enable examinations of sex differences and broader comparative analyses.
Older adults living alone may be more susceptible to social frailty, while they may maintain appetite due to greater autonomy in food selection. However, compared with those living with younger family members or spouses, household composition may be associated with differences in nutritional status and appetite even among individuals in the robust group. Thus, assessing household composition and encouraging appropriate dietary intake may be important for maintaining physical function and potentially mitigating the progression of social frailty. These findings do not indicate causality and should be interpreted cautiously. Further studies are warranted to establish strategies to prevent declines in skeletal muscle mass index among older adults living alone and to assess the prevalence of cohabiting individuals who habitually eat alone.
Conference presentation
This study was presented at the 11th Annual Meeting of the Japanese Society of Nutrition and Swallowing Physical Therapy.
Conflicts of interest
The authors declare no conflicts of interest related to this study.
Acknowledgments
The authors sincerely thank all participants and the staff of Day Service enjoy for their kind cooperation and support in conducting this study.
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