1 Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.
2 Department of Epidemiology, Harvard School of Public Health, Boston, MA.
3 Department of Health and Social Behavior, Harvard School of Public Health, Boston, MA.
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ABSTRACT |
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aged; health status; mental health; social isolation; women
Abbreviations: CI, confidence interval; RR, relative risk; SF-36, Medical Outcomes Study Short-form 36 Health Survey
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INTRODUCTION |
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Social integration may enable the elderly who live alone to maintain independence (6, 9
, 11
). Defined broadly as "concrete involvement of individuals with various aspects of a collectivity," (13
, p. 635) social integration may be divided into two parts: informal networks, such as involvement with friends and relatives, and formal engagement, such as participation in paid employment, clubs, and other organizations; caregiving; and church activities. Social integration has been associated with improved physical and mental health, as well as with longevity (13
16
). Few studies have assessed the extent to which components of social integration may mediate the association between living arrangement and health (6
).
We examined prospectively the relation between living arrangement and 4-year change in functional health status. In addition, we examined whether health differences by living arrangement could be explained by social integration.
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MATERIALS AND METHODS |
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Of the 36,122 noninstitutionalized women aged 60 years or older who responded to the 1992 quality-of-life questionnaire (67 percent of the surviving cohort aged 60 years or older in 1992), 32,102 also responded in 1996 (1,051 of the nonrespondents died before the 1996 follow-up). Compared with women who responded to the quality-of-life questionnaire in 1992 and 1996, surviving women who responded only at baseline were older; had lower scores on physical function, vitality, and mental health; and were more likely to be living alone or with a nonspouse other. Of the women eligible to participate in this study, those with missing data on living arrangement, outcome variables, social network, or covariates (including age, marital status, smoking status, physical activity, body mass index, or alcohol consumption) were excluded (n = 3,778); data from the remaining 28,324 women were used for these analyses.
Measures
Living arrangement.
Women were categorized into three mutually exclusive groups according to living arrangement in 1992: living alone, living with a spouse, and living with people (person) other than a spouse.
Social networks and support.
Characteristics of social networks were assessed by using questions taken from the Berkman-Syme Social Network Index (18), e.g., number of close friends or relatives, contact with close friends and relatives, as well as number of living children. Presence of a confidant was also assessed.
Social engagement.
Activities indicating social engagement were selected to be consistent with "productive" roles that were positively associated with health in previous studies (1921
). Four items comprising the index were: "How often do you go to religious meetings or services?" (regular (one or more times per week) vs. sporadic/never (one to three times per month, less than once per month, rarely or never)), "How many hours each week do you participate in any groups such as social or work group, church-connected group, self-help group, charity, public service, or community group?" (1 or more hours per week vs. none), paid work status (not retired vs. retired), and caregiving (any time per week spent conducting caregiving responsibilities (includes child, grandchild, ill parent, ill other vs. none)). Each item was scored one/zero, and positive responses were summed. Final scores ranged from zero to four. A score of zero indicated no participation, and a score of four indicated participation in all four categories. Women with a score of three or four on the index were combined into one group because of the small number with positive responses in all four categories.
Potential confounders.
Sociodemographic and health covariates collected at baseline (1992) were used. We also considered comorbid conditions diagnosed during follow-up.
Sociodemographic.
We adjusted for age (in years), education, and marital status. Education was described by a five-level categorical variable that combined the educational status of the subject and her spouse. The educational status of the husband was used in addition to the that of the subject because of limited variability in educational attainment among the nurses. Women were categorized as currently married, widowed, or divorced/separated.
Health behaviors.
Health behaviors assessed by questionnaire in 1992 included smoking status, leisure-time physical activity (22), and current weight (23
). Alcohol consumption (24
) was assessed in 1990. For physical activity, we calculated an average total activity score, measured in metabolic-equivalent hours per week based on frequency of engagement in eight common leisure-time physical activities. Body mass index (weight (kg)/height (m2)) was calculated from height reported on the original 1976 questionnaire and body weight reported on the 1992 questionnaire.
Number of baseline comorbid conditions.
Past personal history of heart disease, stroke, myocardial infarction, cancer, diabetes, arthritis, osteoporosis, or hypertension was assessed by the participant's self-report on any previous biennial questionnaire from 1976 to 1992 (25). The number of self-reported chronic conditions at baseline was summed.
Incident comorbid conditions (19921996).
Incidence of cancer, heart disease (myocardial infarction or angina), stroke, hypertension, or diabetes between 1992 and 1996 was measured from respondents' 1994 and 1996 reports of newly diagnosed conditions since the 1992 questionnaire.
Outcome variable.
The Medical Outcomes Study Short-form 36 Health Survey (SF-36) (26), a multidimensional measure of function health status, was included in a supplemental questionnaire in 1992 and 1996. The SF-36 has been used in clinical and epidemiologic studies and is internally consistent, reliable, and predictive of health outcomes in a variety of populations (27
29
).
To maintain consistency with previous epidemiologic studies of the association between living arrangement and health status, we focused on three of the eight subscales measured by the SF-36: physical function, vitality, and mental health. Scale scores were computed by summing across all items in the same scale and transforming raw scale scores to range from zero (worst possible function) to 100 (best possible function) (26).
Change in functional health status over the 4-year follow-up was measured for each scale by subtracting the participant's score in 1992 (baseline) from the participant's score in 1996. Three groups of subjects were defined: those whose function declined, improved, and remained stable (30). Functional status decline was defined by a drop of 10 or more points. Improvement in functional health status was defined as a gain of 10 or more points. Remaining subjects were classified as stable, meaning that their functional status in 1996 was within 10 points of their 1992 status. A conservative cutoff of 10 points was selected based on prior research (30
). To test the sensitivity of the 10-point cutoff, we compared our results with results obtained using a five-point cutoff and a 15-point cutoff. Finding no material difference between these analyses, we report the results using the 10-point cutoff.
Statistical analysis
We assessed associations between living arrangement and decline in function by using logistic regression. Separate models were fit for each functional health status subscale. We estimated the relative risks of decline in functional health status associated with living alone or living with nonspouse other compared with living with a spouse (the reference group). We examined four sets of models. In the primary analysis, we modeled the association between living arrangement and change in functional health status, adjusted for age (in years) and the following covariates: baseline functional status, education, body mass index (<25, 2529.9, and 30 units), alcohol consumption (none, 1149, and
150 g per week), smoking (never, former, or current smokers of 114, 1524, and
25 cigarettes per day), physical activity (quintiles of metabolic-equivalent hours per week), number of comorbid conditions at baseline (zero, one, or two or more), and incident comorbid conditions between 1992 and 1996. Marital status was not included as a covariate in the primary analysis because of its close association with living arrangement; more than 99 percent of the women living with a spouse reported that they were married, and more than 70 percent of the women living alone or with nonspouse others reported that they were widows. We conducted a secondary analysis, including marital status as a covariate to compare the results with the analysis without marital status.
In a second set of analyses, we fit models containing not only the original covariates but also living arrangements plus social network/support characteristics. "Number of close friends and relatives" and "contact with close friends and relatives" were highly collinear. Therefore, we chose to include only "contact with close friends and relatives" (high contact vs. moderate or low contact), which accounted for more of the variance in functional decline. In addition to contact with close friends and relatives, we included the following social network/support characteristics: number of living children (three or more vs. zero to two) and presence or absence of a confidant. In a third set of analyses, we added level of social engagement (score of one, two, or three vs. zero) to all the other covariates. We compared the relative risks for living arrangement obtained in the first model with those obtained in the second and third models.
Finally, within strata of living arrangement, we examined social networks/support and social engagement index separately as predictors of change in physical function, vitality, and mental health, controlling for other covariates.
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RESULTS |
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To eliminate the situation for which living with a spouse may be related to extraordinary physical or emotional demands, we repeated the primary analysis, excluding women who reported providing care for an ill spouse at baseline or at follow-up. Additionally, to address the problem of reverse causation, i.e., that a change in functional status over the 4-year follow-up period might result in a change in living arrangement, we repeated the analysis, excluding women whose living arrangement in 1996 was different from that reported at baseline. After exclusion of 8,833 women who reported providing any care for an ill spouse at baseline or in 1996, living alone compared with living with a spouse remained associated with less risk of decline for mental health (RR = 0.79, 95 percent CI: 0.69, 0.90) and marginally associated with less risk of decline for vitality (RR = 0.91, 95 percent CI: 0.84, 1.00). Results also remained materially unchanged after exclusion of women who reported any change in living arrangement from 1992 to 1996 (n = 3,235). The multivariate-adjusted relative risk for mental health comparing women living alone with those living with a spouse changed from 0.73 to 0.77 (95 percent CI: 0.68, 0.87).
To explore further the association between living alone and mental health, we conducted another analysis modeling odds of improvement in mental health (compared with odds of remaining stable) and controlling for the same covariates as in the primary model. Women whose mental health declined were excluded from this analysis. Women living alone were 31 percent more likely to improve in mental health than were women living with a spouse (RR = 1.31, 95 percent CI: 1.20, 1.44).
We examined the sensitivity of the 10-point cutoff for change in health status by rerunning the primary analyses using different cutoff points: e.g., five and 15 points. The effect estimates were similar with the different cutoff points, but the standard errors were slightly smaller using the 5-point cutoff and were larger using the 15-point cutoff. The significance of two marginal results was changed using the 5-point cutoff. The association between living with a nonspouse other (vs. living with a spouse) and a 5-point decline in physical function lost statistical significance (RR = 1.09, 95 percent CI: 0.97, 1.22), and the association between living with a nonspouse other (vs. living with a spouse) and a 5-point decline in mental health became statistically significant (RR = 0.83, 95 percent CI: 0.73, 0.97).
Social network characteristics and our social engagement index were significantly associated with all three dimensions of change in functional status in univariate analyses; the only exception was that number of living children was not associated with change in vitality. After the addition of social network characteristics to the model (table 3), the relative risk estimates for living arrangements were not different from the relative risk found without control for social networks. Similarly, the relative risk estimates remained unchanged after the addition of social engagement index in addition to the social network characteristics (table 3).
Change in functional health status within strata of living arrangement
The results from multivariate models within strata of living arrangement (table 4) suggest that for women living with a spouse, only the highest level of social engagement and the presence of a confidant were significantly associated with a decline in mental health. Among women living alone, social engagement and social network variables (e.g., contact with friends and relatives) were strongly associated with a decreased risk of decline in mental health. Neither social engagement nor any of the social network variables was significantly associated with a change in vitality among women living alone. In contrast, social networks (contact with friends and relatives) and social engagement were moderately associated with less risk of decline in vitality for women living with a spouse. Among women living with someone other than a spouse, social engagement was significantly associated with a lower risk of decline in vitality. In addition, a modest, but statistically nonsignificant, association was suggested for physical function and mental health.
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DISCUSSION |
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This study confirmed results from recent longitudinal studies (8, 10
, 11
) that older women who live alone are not at increased risk of decline in physical function compared with women who live with their spouses after controlling for physical function at baseline, as well as other covariates. Not previously examined in longitudinal analyses, living alone was strongly associated with less decline in mental health and was moderately associated with less decline in vitality. Our results for mental health were surprising, given the strong association between living alone and poor well-being in cross-sectional studies as well as evidence that widowhood is associated with depression and other poor outcomes (19
). Indeed, the cross-sectional association we observed at baseline among our population suggested that mental health, along with physical function and vitality, was higher among those women living with a spouse compared with those living alone. A review of the widowhood and mental health literature concludes that there is little doubt that recent bereavement is associated with greater risk of depression (31
). However, the impact of bereavement on health outcomes is strongest in the short term and is attenuated with time since bereavement (31
). The association also seems to vary by gender, with men experiencing worse health outcomes than did women (32
). More than 100 years ago, Durkheim (33
) suggested that marriage may not provide the same protection for women that it does for men, that "women can suffer more from a marriage if it is unfavorable to her than she can benefit by it if it conforms to her interest. This is because she has less need of it" (33
, p. 275). In addition, a woman is more likely than a man to maintain a family structure if divorced or widowed.
One of the hypothesized mechanisms underlying the living arrangement-functional status relation is social ties and involvement (34). It has been proposed that social interaction provides a buffer between general stress (for example, stressful life events) and physical or psychologic health (16
). Given this model, Kasper and Pearson (6
) suggest that social interaction may be more important for persons living alone, who tend to have less income and to be in poorer health in contrast to those living with a spouse. While the protective effect of living alone was not mediated by social network or engagement characteristics in our study, contact with friends and relatives and social engagement were independently protective of decline in mental health among women living alone.
There are limitations to this study. We did not have information on how long the women had been in the living arrangement prior to 1992. The duration of the living situation (for example, women who had lived alone for many years compared with women who had just begun to live in a single-person household after the death of a spouse) may have influenced the change in health observed between 1992 and 1996. We did find that part of the decline in mental health among women living with a spouse compared with those living alone in 1992 was due to the 10 percent of women who were no longer living with their spouse by the time of the 1996 survey, but excluding these women did not change the results materially.
We also did not have information on why women were living alone. Sarwari et al. (8) pointed out that the "advantage" to living alone may reflect a preference for independent living expressed as a health benefit in terms of decreased functional reliance on others. Lawton et al. (5
) emphasized that any observed association between living arrangement and health may have more to do with factors and characteristics that are idiosyncratic to the individual and her choice to live alone. The absence of information regarding individual motivation limits our ability to identify the mechanism relating living arrangement to health, but does not diminish the strength of the association that we observed.
A potential validity concern lies in the selective survival of the women who completed the follow-up functional status questionnaire, namely that 1) those who became widowed have a higher rate of death and attrition, and hence may not have been represented in our study sample, and thus that 2) among women who survived and were included in our study sample, those living alone did better on mental health than those who stayed married. To test for a healthy survivor bias in our sample, we checked whether women who became widowed after 1976 had increased rates of mortality and attrition compared with those who stayed married. Among women who reported in 1992 that they were widows, 14.1 percent were lost to follow-up in 1996 due to death or attrition. Among women who reported in 1992 that they were married, only 10.2 percent were lost to follow-up in 1996 due to death or attrition. This suggests that widows were slightly more likely to die or become infirm during the study period than were married women, but the difference was small. External validity remains a limitation of this study. On average, women who responded in 1992 and 1996 and thus were included in our analysis were healthier than those who responded only in 1992. However, the difference in baseline mental health and vitality was small and was not clinically meaningful (two and four points, respectively).
Strengths of this study lie in its prospective design, allowing us to measure individual change in functional health status. Additionally, unlike in other prospective studies (8, 11
), we were able to control for individual-level health behaviors as well as for the effects of changes in functional health arising from catastrophic medical events such as stroke, cancer diagnosis, or myocardial infarction. We were also able to exclude the effects of caregiving for an ill spouse as well as changes in living arrangements during the follow-up period. The study also benefitted from our use of an outcome measure that examined dimensions of function beyond physical health. Finally, we were able to consider the potentially mediating effect of social network and social engagement variables in addition to living arrangements.
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ACKNOWLEDGMENTS |
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The authors thank Dr. Richard Gelber for statistical help and advice.
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NOTES |
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REFERENCES |
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