- Email: [email protected]
Social Support, Depression, and Functional Disability in Older Adult Primary-Care Patients
Social Support, Depression, and Functional Disability in Older Adult Primary-Care Patients Linda A. Travis, Psy.D., Jeffrey M. Lyness, M.D. Cleveland G. Shields, Ph.D., Deborah A. King, Ph.D. Christopher Cox, Ph.D.
Objective: The authors asked whether social support and depression are independently associated with functional disability and examined the potential role of social support as a moderator in the depression–functional disability association. Methods: Subjects were 305 patients age 60 years and over. Predictor variables were social support, depressive symptoms, and depression diagnosis. Dependent variables were the Instrumental Activities of Daily Living Scale, the Physical Self-Maintenance Scale, and the Physical Functioning subscale of the Medical Outcomes Study 36-Item ShortForm Health Survey. Authors used multiple-regression analyses. Results: Depressive symptoms and all dimensions of social support were independently associated with functional disability: the specifics of these relationships varied among types of social support and functional disability. Depression diagnosis was not independently associated with any functional disability measure. Social support (more instrumental help, more perceived satisfaction) moderated some depression diagnosis–functional disability associations, and one depressive symptom–functional disability association. Conclusions: The study hypotheses were partially confirmed. Different dimensions of social support have important and varied roles in the depression–functional disability dynamic. Future research is needed to further specify the complex relationships among depression, social support, and functional disability. (Am J Geriatr Psychiatry 2004; 12:265–271)
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robust association between depression and functional disability has been demonstrated for older adults in psychiatric,1,2 medical,3,4 community,5 and primary-care6 settings.
A necessary next step is to identify specific factors that may protect against, or increase susceptibility to, the development of depression and functional disability.7 Moderators influence the direction or strength of
Received October 18, 2002; revised January 21, 2003; accepted February 12, 2004. From the Laboratory of Depression and Medical Comorbidity, Program in Geriatrics and Neuropsychiatry, Department of Psychiatry, University of Rochester Medical Center (URMC), Rochester, NY (LAT,JML,DAK); the Wynne Center for Family Research, Department of Psychiatry URMC (LAT,CGS); the Department of Family Medicine, URMC (CGS); the Department of Biostatistics and Computational Biology, URMC (CC); and the Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, Department of Health and Human Services, Bethesda, MD (CC). Send correspondence to Jeffrey M. Lyness, M.D., Department of Psychiatry, University of Rochester Medical Center, 300 Crittenden Boulevard, Rochester, NY 14642. e-mail: [email protected] 䉷 2004 American Association for Geriatric Psychiatry
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Social Support, Depression, and Disability a relationship between an independent variable and a dependent variable.8,9 Identifying moderators in the depression and functional disability association is important in order to design and evaluate health and mental health interventions aiming to slow or prevent functional disability, an objective with significant clinical and public-health implications.7,10,11 Also, primary care is a particularly important setting in which to study the depression and functional disability association,6,12 as most community-dwelling older adults with depressive symptoms and disorders do not seek care in conventional mental-health settings, but are seen, instead, in primary care.13 Social support is a crucial factor to consider in the depression–disability dynamic. Older adults’ daily functioning occurs within a social network of relationships with family, friends, and community members. Social-support theories14,15 conceptualize the social network as having a structural dimension (i.e., size of social network; frequency of social network interactions) and a functional dimension (i.e., emotional and instrumental components of interactions). Findings have been equivocal regarding the structural dimension of social support; it is unclear whether the size and frequency of social network interactions2,10 or the quality16–18 of the interactions predict more functional impairment. In contrast, research on the emotional component of support has consistently revealed that reports of less satisfying relationships are associated with more functional impairment,2,19,20 a greater number of depressive symptoms,21–23 and the presence of major depression.24,25 Regarding the instrumental component of functional support for older adults, studies to date have not obtained consistent results in identifying whether more2 or less26 instrumental support is associated with functional disability and depression. In summary, poorer emotional support is associated with more depressive symptoms, major depression, and greater functional disability, whereas neither structural nor instrumental support has a consistent relationship with these same variables. Two studies examined the buffering role of social support. In a naturalistic study of older adults diagnosed with major depression,24 social support moderated the depression and functional disability association: structural and emotional dimensions of social support protected against more decline in basic activities of daily living among the most depressed pa-
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tients. In a treatment study of dysthymia and minor depression in older primary-care patients,27 larger social networks making frequent contact were related to more adequate emotional support, which was then associated with decreases in depression in the placebo but not in the treatment groups. These studies highlight the importance of distinguishing among types of social support and types of functional disability. They also suggest the need for further research to examine ways in which social support may moderate the depression–functional disability association. Only one of the social support investigations cited above27 involved older patients in primary care, and few included longitudinal analyses.21,24,27 To our knowledge, no naturalistic study has investigated social support as a moderator in the association between depression and functional disability for older adults in primary care. We tested the following hypotheses in cross-sectional and longitudinal analyses: 1) social support and depression (measured both by diagnosis and symptom severity) are independently associated with functional disability; and 2) social support moderates the association of depression with functional disability.
METHODS The subjects in this study were part of a sample described previously,28 recruited from private internalmedicine offices or a family medicine clinic. All patients 60 years old and over who gave formal verbal informed consent (procedure approved by the University of Rochester Research Subjects Review Board) were eligible to participate. Data were obtained at study intake and 1-year follow-up by trained raters. Depression diagnoses were assigned on the basis of the Structured Clinical Interview for DSM-III-R (SCID).29 Study diagnostic groups were defined as follows: no depression, current major depression, and current minor depression. The diagnosis of minor depression was based on the criteria in the appendix to DSM-IV; this definition required that there be no previous history of major depression. Depressive symptoms were measured by the 24-item version of the Hamilton Rating Scale for Depression (Ham-D),30 a widely used examiner-rated scale.
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Travis et al. Three functional measures were used. The Instrumental Activities of Daily Living scale includes eight items assessing instrumental activities such as preparing food and managing money.31 The Physical Self-Maintenance scale has six items assessing abilities in basic activities such as feeding and continence.31 Both are widely used throughout research with older adults. Examiners based their ratings for these measures on interview data and from reviews of medical charts. Higher scores for both measures represent more functional disability. Assessment of functional status regarding higher-level activities was measured from the Physical Functioning subscale, that is, Questions 3–12, of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36),32 a self-report instrument. The questions in this subscale ask the subject to identify the degree to which physical health limits participation in high-effort, moderate-effort, and low-effort daily activities. The scores were transformed to a scaled score from 0–100 as per the SF-36 manual.33 Lower scores represent more functional disability. In this report, the three measures of functional disability will be referred to as instrumental, basic, and broad, respectively. Three dimensions of social support were assessed: frequency of social interaction with others, level of perceived satisfaction with others, and amount of instrumental help from others. These dimensions were measured by the corresponding three subscales of the Duke Social Support Index (DSSI).34 The analyses used multiple-regression techniques to determine independent associations between predictor and dependent variables. Poisson (log-linear) regression was used, with an adjustment for extraPoisson variation, because two dependent variables, instrumental and basic disability, were discrete, with skewed distributions. Parameter estimates (coefficients and standard error [SE]) are reported for the independent variables of interest; for patients with a depression diagnosis, the reference group (i.e., coefficient⳱0) was the nondepressed group. Two-tailed p-values were used, establishing a more conservative level of significance, given the large number of tests performed, and alpha was set at 0.05. Multicollinearity was not a problem in these analyses because a correlation matrix among the independent variables showed all correlations to be ⬍0.38. Age, gender, and medical illness burden (Cumulative Illness Rating Scale [CIRS])35 were covaried in all analyses. Baseline
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functional disability was controlled for in all longitudinal analyses. All analyses were performed both cross-sectionally (examining the relationship among variables at study intake) and longitudinally (examining the relationships between intake variables and 1-year functional outcomes). The first set of analyses examined the independent associations of social support and depression diagnosis with the functional measures. To examine social support’s moderator role, a multiplicative interaction term (depression diagnosis ⳯ social support) was then entered as the independent variable, also covarying the main-effects variables. The second set of analyses was similar, except that depressive symptoms, rather than depression diagnosis, were used.
RESULTS Table 1 shows the descriptive results. There were 305 subjects at intake, of which 31 had major depression; 19 had minor depression; and 255, no depression diagnosis. Of these, 247 completed 1-year assessments, 14 had died, and 44 refused or were not available for follow-up interviews. Compared with the living subjects who did not complete follow-up assessments,12 the 247 subjects who did so did not differ significantly on age, gender, or CIRS score, but had more education (mean [standard deviation {SD}]: 13.4 [2.8] years versus 12.2 [3.1] years; t[55.8]⳱ –2.5; p⳱0.02). At follow-up, 22 subjects had major depression, 14 had minor depression, and 211 no depression diagnosis. We first report the analyses examining the independent associations of depression diagnosis and social support with functional disability (Hypothesis #1), beginning with instrumental disability. Two of the three dimensions of social support (less social interaction and more instrumental help) were associated with more instrumental disability (coefficient [SE] for less social interaction: –0.20 [0.07];F[1, 294]⳱ 7.21; p⳱0.008; and for more instrumental help: –0.17 [0.06]; F[1, 294]⳱9.87; p⳱0.002). Depression diagnosis was not independently associated with instrumental or basic disability. No type of social support was associated with basic disability. Depression diagnosis was also not associated with broad disability, but two of the three dimensions of social support were
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Social Support, Depression, and Disability (perceived satisfaction: coefficient [SE]: 1.48 [0.75]; F[1, 294]⳱3.93; p⳱0.048; and instrumental help: 1.49 [0.73], F[1, 294]⳱4.21; p⳱0.041). In longitudinal analyses, depression diagnosis was not associated with any type of functional disability, nor was any dimension of social support independently associated with instrumental or broad disability. Less social interaction was independently associated with basic disability (coefficient [SE]: –0.15 [0.07]; F[1, 238]⳱4.86; p⳱0.029). To test the moderator effects as stated in Hypothesis #2, we examined the independent association of interaction terms (i.e., depression diagnosis ⳯ each social support subscale) with each functional measure. We first report the cross-sectional results. The interaction of depression diagnosis and social interaction was not independently associated with any type of functional disability. The interaction of depression diagnosis and more perceived satisfaction was not independently associated with instrumental or basic disability, but was associated with more broad disability (coefficient [SE] for major depression: –4.51 [1.57]; for minor depression: –6.47 [4.23]; F[1, 292]⳱ 4.91; p⳱0.008). The interaction of depression diagnosis and more instrumental help was not independently associated with instrumental disability, but was significantly associated with both basic disability (coefficient [SE] for major depression, –0.22 [0.09]; for minor depression, –0.59 [0.23]; F[1, 292]⳱6.58; p⳱0.002) and broad disability (coefficient [SE] for major depression, 4.05 [1.77]; for minor depression,
TABLE 1.
4.55 [3.08]; F[1, 292]⳱3.39; p⳱0.035). In the longitudinal analyses of moderator effects, none of the depression diagnosis–social support interaction terms were independently associated with functional outcomes. We now turn to the analyses examining the independent associations of depressive symptoms and social support with functional disability (Hypothesis #1), beginning with instrumental disability. Two of the three dimensions of social support (less social interaction and more instrumental help) were associated with more instrumental disability (coefficient [SE] for social interaction: –0.18 [0.07]; F[1, 295]⳱6.45; p⳱0.012; instrumental help: –0.14 [0.05]; F[1, 295]⳱ 6.81; p⳱0.010). Having more depressive symptoms was associated with having more instrumental disability (coefficient [SE]: 0.04 [0.01]; F[1, 295]⳱10.17; p⳱0.002); more basic disability (coefficient [SE]: 0.04 [0.01]; F[1, 295]⳱8.45; p⳱0.004), and more broad disability (coefficient [SE]: –1.04 [0.25]; F[1, 295]⳱17.38; p⳱⬍0.000). Social support was not associated with basic or broad disability. In longitudinal analyses, depressive symptoms and social support were not associated with instrumental or broad disability. Social support (less social interaction) was associated with basic disability (coefficient [SE]: –0.14 [SE] 0.07; F[1, 239]⳱3.92; p⳱0.049). In moderator analyses (Hypothesis #2): No depressive symptoms–social support interaction terms were associated with instrumental or basic disability, but the interaction of depressive symptoms and more perceived satisfaction was associated with broad dis-
Descriptive results, mean (standard deviation)
Variable
At Intake (Nⴔ305; 183 [60%] Women)
One-Year Follow-Up (Nⴔ247; 145 [59%] Women)
Age, years CIRS IADL PSMS PHYFXN Ham-D DSSI-SOC DSSI-PSS DSSI-IS
71.3 (7.6); range: 60–94 6.2 (3.0); range: 0–16 2.3 (4.5); range: 0–20 1.0 (1.8); range: 0–15 56.8 (29.7); range: 0–100 8.6 (6.8); range: 0–34 8.9 (1.4); range: 5–12 19.3 (2.4); range: 8–21 14.9 (2.3); range: 12–24
71.1 (7.5); range: 60–94 6.8 (3.0); range: 1–17 2.3 (4.4); range: 0–24 1.1 (2.1); range: 0–15 58.1 (29.5); range: 0–100 7.3 (5.7); range: 0–30 8.8 (1.5); range: 5–12 19.3 (2.3); range: 8–21 15.3 (2.2); range: 12–24
Note: Values are mean (standard deviation). CIRS: Cumulative Illness Rating Scale; Ham-D: Hamilton Rating Scale for Depression; IADL: Instrumental Activities of Daily Living; PSMS: Physical Self-Maintenance Scale; PHYFXN: Physical Functioning subscale from Medical Outcomes Study–Short Form-36; DSSI-SOC: Duke Social Support Inventory–Social Interaction Subscale; DSSI-PSS: Duke Social Support Inventory–Perceived Satisfaction Subscale; DSSI-IS: Duke Social Support Inventory–Instrumental Help Subscale.
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Travis et al. ability (coefficient [SE]: –0.24 [0.09]; F[1, 294]⳱6.70; p⳱0.010). In longitudinal analyses, no interaction terms were significant.
CONCLUSIONS Our first hypothesis was partially confirmed; depressive symptoms and all dimensions of social support were independently associated with more functional disability, although the specifics of these relationships varied among types of social support and functional disability. Our second hypothesis was also partially confirmed; social support (more instrumental help, more perceived satisfaction) was a moderator in a few depression diagnosis–functional disability crosssectional associations. Overall, our results underscore the call for functional disability to be investigated through the use of instruments assessing instrumental, basic, and broad aspects of functional disability, through self-rated and examiner-rated methods, and at cross-sectional and longitudinal time-points.7,36 Our study is also unique in demonstrating the complex relationships among depression, social support, and multiple types of functional disability within a primary-care sample. Older patients in primary care are characterized by heterogeneity in physical and emotional functioning, and this heterogeneity is at once a unique feature and a drawback for investigators. We do note here that our subjects’ overall instrumental and basic disability at baseline and follow-up were comparable to that found in community residents,37 rather than in psychiatric patients.24 The inclusion of dimensional and categorical assessments of depression, however, highlighted important distinctions across hypotheses between depressive symptoms and depression diagnosis. For example, significant moderator results were obtained primarily in analyses using depression diagnosis; these results are in keeping with another study examining social support as moderator in a sample of more severely depressed and disabled elderly patients drawn from a psychiatric setting.24 In sum, it is crucial to use an integrative framework that addresses both the heterogeneity of phenomena across the sample as well as the homogeneity of phenomena for specified sample subgroups in older adult primary care studies.
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Closer examination of results from each of the three dimensions of social support highlights the important and varied roles of social support in association with different types of functional disability. Our most uniform finding was the association of more instrumental help with all types of functional disability. Main effects for more instrumental help were associated with more instrumental disability across analyses of depressive symptoms and diagnoses. However, although instrumental help moderated the association between depression diagnosis and both basic and broad disability, instrumental help did not moderate any of the depressive symptom–functional disability associations. Variation in the moderating roles for instrumental help point to the need for researchers to further specify how and when receiving help from others may directly or indirectly affect different types of functional disability, with particular attention to potentially distinct interactions with depression diagnoses versus depressive symptoms. Regarding frequency of interaction, less social interaction was associated with more instrumental disability across analyses of both depressive symptoms and diagnoses. This result is consistent with previous findings in a psychiatric setting2 and further underscores the potent social and environmental features imbedded in instrumental functioning.31 However, unlike that cross-sectional study,2 we consistency found that less social interaction was associated with greater basic disability at 1 year. Leisure, social, or other discretionary activities may be among the first to show decline38,39 and thereby signal a temporary or long-term change in functional status. Indeed, low frequency of contact with others has been identified as an independent risk factor for functional disability in those with2,24 and without10 a depression diagnosis. Thus, it may be helpful for health care providers to ask older patients about changes in the frequency of social interactions. However, providers need to remain cognizant that changes in the frequency of social interactions may be adaptive, given the desire to conserve resources, and thus may not reflect a poorer quality of interactions.38,40 In contrast to other social-support studies with elderly subjects,2,24,25 less perceived satisfaction was not associated with instrumental or basic disability, although it was independently associated with broad disability, the one measure of self-rated functional disability in our study. Also, the interaction of de-
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Social Support, Depression, and Disability pression diagnosis and more perceived satisfaction was associated with broad disability. Because more perceived satisfaction has been independently associated with less functional disability in elderly patients with major depression in a naturalistic treatment study24 and with decreases in depression in a treatment study of primary-care elderly patients,27 our findings merit comment. Perhaps those depressed older patients who enter treatment studies are less satisfied with their social network and thereby represent a different population than those primary care patients in our naturalistic study. It is also possible that older adults proactively adapt and manage functional and emotional disability through having more satisfaction with others involved in their social network.38,40 Our results must be considered in the context of other study limitations. Our study group was largely “young-old,” predominantly white, and relatively well educated for an older cohort: these findings may not generalize to other populations. Also, we did not collect data about several other dimensions of social support, such as negative as well as positive interactions,41 providing as well as receiving support,42 or the distinctions between support from family members or friends.43 In summary, social support has important and varied roles in relation to functional disability and the depression–functional disability dynamic. Our findings contribute to knowledge of this area through the
use of multiple functional disability measures, as well as categorical and dimensional measures of depression in a heterogeneous primary-care group. Future research is needed to specify the complex relationships among depression, social support, and functional disability, cross-sectionally and over longerterm follow-up periods. Most importantly, striving to understand ways to slow the progression of functional disability is a goal with significant clinical and public-health implications.7,10,11 This work was presented in part at the Annual Meeting of the American Association for Geriatric Psychiatry, San Francisco, CA, February 25, 2001, and the Gerontological Society of America, Chicago, IL, November 15, 2001. The authors thank T.K. Noel, C. Doane, A. Wisner, A. Gleason, G. Kiernan, H. Stiner, and Z. Yoediono for technical assistance, and the patients and staff of the offices of Drs. J. Allen, M. Bergin, M. Berliant, C. Conners, R. Greene, M. Labanowski, R. Maggio, B. Peyser, and R. Pincus, and the Family Medicine Center at Highland Hospital. We thank the URMC Department of Biostatistics and Computational Biology research associate Shirley Eberly, M.S., and programmer Carrie Irvine, B.S., for their assistance in preparation of this manuscript. This work was supported by National Institute of Mental Health, grants K07-MH01113 (Dr. Lyness) and T32 MH18911 (E.D. Caine, M.D., PI).
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Travis et al. book of Health Psychology. Edited by Baum A, Revenson TA, Singer JE. Mahwah, NJ, Lawrence Erlbaum Associates, 2001, pp 209–234 15. Berkman LF, Glass T, Brissette I, et al: From social integration to health: Durkheim in the new millennium. Soc Sci Med 2000; 51:843–857 16. Seeman TE: Social ties and health: the benefits of social integration. Ann Epidemiol 1996; 6:442–451 17. Seeman TE, Syme SL: Social networks and coronary artery disease: a comparison of the structure and function of social relations as predictors of disease. Psychosom Med 1987; 49:341–354 18. Lang FR, Carstensen LL: Close emotional relationships in later life: further support for proactive aging in the social domain. Psychol Aging 1994; 9:315–324 19. Berkman LF: The relationship of social networks and social support to morbidity and mortality, in Social Support and Health. Edited by Cohen S, Syme SL. Orlando, FL, Academic Press, 1985, pp 241–262 20. Berkman L: The role of social relations in health promotion. Psychosom Med 1995; 5:245–254 21. Oxman TE, Berkman LF, Kasl S, et al: Social support and depressive symptoms in the elderly. Am J Epidemiol 1992; 135:356–368 22. Koenig HG, Hays JG, George LK, et al: Modeling the cross-sectional relationships between religion, physical health, social support, and depressive symptoms. Am J Geriatr Psychiatry 1997; 5:131–144 23. Blazer DG, Hughes DC, George LK: Age and impaired subjective support: predictors of depressive symptoms at one-year followup. J Nerv Ment Dis 1992; 31:148–161 24. Hays JC, Steffens DC, Flint EP, et al: Does social support buffer functional decline in elderly patients with unipolar depression? Am J Psychiatry 2001; 58:1850–1855 25. Bosworth HB, Steffens DC, Kuchibhatla MN, et al: The relationship of social support, social networks, and negative events with depression in patients with coronary artery disease. Aging Ment Health 2000; 4:253–258 26. Newson JT, Schultz R: Social support as a mediator in the relation between functional status and quality of life in older adults. Psychol Aging 1996; 11:34–44 27. Oxman TE, Hull JG: Social support and treatment response in older depressed primary care patients. J Gerontol B Psychol Sci Soc Sci 2001; 56B:P35–P45 28. Lyness JM, Caine ED, King DA, et al: Psychiatric disorders in older primary care patients. J Gen Intern Med 1999; 14:249–254 29. Spitzer RL, Williams JBW, Gibbon M: Structured Clinical Inter-
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Objective: The authors asked whether social support and depression are independently associated with functional disability and examined the potential role of social support as a moderator in the depression–functional disability association. Methods: Subjects were 305 patients age 60 years and over. Predictor variables were social support, depressive symptoms, and depression diagnosis. Dependent variables were the Instrumental Activities of Daily Living Scale, the Physical Self-Maintenance Scale, and the Physical Functioning subscale of the Medical Outcomes Study 36-Item ShortForm Health Survey. Authors used multiple-regression analyses. Results: Depressive symptoms and all dimensions of social support were independently associated with functional disability: the specifics of these relationships varied among types of social support and functional disability. Depression diagnosis was not independently associated with any functional disability measure. Social support (more instrumental help, more perceived satisfaction) moderated some depression diagnosis–functional disability associations, and one depressive symptom–functional disability association. Conclusions: The study hypotheses were partially confirmed. Different dimensions of social support have important and varied roles in the depression–functional disability dynamic. Future research is needed to further specify the complex relationships among depression, social support, and functional disability. (Am J Geriatr Psychiatry 2004; 12:265–271)
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robust association between depression and functional disability has been demonstrated for older adults in psychiatric,1,2 medical,3,4 community,5 and primary-care6 settings.
A necessary next step is to identify specific factors that may protect against, or increase susceptibility to, the development of depression and functional disability.7 Moderators influence the direction or strength of
Received October 18, 2002; revised January 21, 2003; accepted February 12, 2004. From the Laboratory of Depression and Medical Comorbidity, Program in Geriatrics and Neuropsychiatry, Department of Psychiatry, University of Rochester Medical Center (URMC), Rochester, NY (LAT,JML,DAK); the Wynne Center for Family Research, Department of Psychiatry URMC (LAT,CGS); the Department of Family Medicine, URMC (CGS); the Department of Biostatistics and Computational Biology, URMC (CC); and the Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, Department of Health and Human Services, Bethesda, MD (CC). Send correspondence to Jeffrey M. Lyness, M.D., Department of Psychiatry, University of Rochester Medical Center, 300 Crittenden Boulevard, Rochester, NY 14642. e-mail: [email protected] 䉷 2004 American Association for Geriatric Psychiatry
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Social Support, Depression, and Disability a relationship between an independent variable and a dependent variable.8,9 Identifying moderators in the depression and functional disability association is important in order to design and evaluate health and mental health interventions aiming to slow or prevent functional disability, an objective with significant clinical and public-health implications.7,10,11 Also, primary care is a particularly important setting in which to study the depression and functional disability association,6,12 as most community-dwelling older adults with depressive symptoms and disorders do not seek care in conventional mental-health settings, but are seen, instead, in primary care.13 Social support is a crucial factor to consider in the depression–disability dynamic. Older adults’ daily functioning occurs within a social network of relationships with family, friends, and community members. Social-support theories14,15 conceptualize the social network as having a structural dimension (i.e., size of social network; frequency of social network interactions) and a functional dimension (i.e., emotional and instrumental components of interactions). Findings have been equivocal regarding the structural dimension of social support; it is unclear whether the size and frequency of social network interactions2,10 or the quality16–18 of the interactions predict more functional impairment. In contrast, research on the emotional component of support has consistently revealed that reports of less satisfying relationships are associated with more functional impairment,2,19,20 a greater number of depressive symptoms,21–23 and the presence of major depression.24,25 Regarding the instrumental component of functional support for older adults, studies to date have not obtained consistent results in identifying whether more2 or less26 instrumental support is associated with functional disability and depression. In summary, poorer emotional support is associated with more depressive symptoms, major depression, and greater functional disability, whereas neither structural nor instrumental support has a consistent relationship with these same variables. Two studies examined the buffering role of social support. In a naturalistic study of older adults diagnosed with major depression,24 social support moderated the depression and functional disability association: structural and emotional dimensions of social support protected against more decline in basic activities of daily living among the most depressed pa-
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tients. In a treatment study of dysthymia and minor depression in older primary-care patients,27 larger social networks making frequent contact were related to more adequate emotional support, which was then associated with decreases in depression in the placebo but not in the treatment groups. These studies highlight the importance of distinguishing among types of social support and types of functional disability. They also suggest the need for further research to examine ways in which social support may moderate the depression–functional disability association. Only one of the social support investigations cited above27 involved older patients in primary care, and few included longitudinal analyses.21,24,27 To our knowledge, no naturalistic study has investigated social support as a moderator in the association between depression and functional disability for older adults in primary care. We tested the following hypotheses in cross-sectional and longitudinal analyses: 1) social support and depression (measured both by diagnosis and symptom severity) are independently associated with functional disability; and 2) social support moderates the association of depression with functional disability.
METHODS The subjects in this study were part of a sample described previously,28 recruited from private internalmedicine offices or a family medicine clinic. All patients 60 years old and over who gave formal verbal informed consent (procedure approved by the University of Rochester Research Subjects Review Board) were eligible to participate. Data were obtained at study intake and 1-year follow-up by trained raters. Depression diagnoses were assigned on the basis of the Structured Clinical Interview for DSM-III-R (SCID).29 Study diagnostic groups were defined as follows: no depression, current major depression, and current minor depression. The diagnosis of minor depression was based on the criteria in the appendix to DSM-IV; this definition required that there be no previous history of major depression. Depressive symptoms were measured by the 24-item version of the Hamilton Rating Scale for Depression (Ham-D),30 a widely used examiner-rated scale.
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Travis et al. Three functional measures were used. The Instrumental Activities of Daily Living scale includes eight items assessing instrumental activities such as preparing food and managing money.31 The Physical Self-Maintenance scale has six items assessing abilities in basic activities such as feeding and continence.31 Both are widely used throughout research with older adults. Examiners based their ratings for these measures on interview data and from reviews of medical charts. Higher scores for both measures represent more functional disability. Assessment of functional status regarding higher-level activities was measured from the Physical Functioning subscale, that is, Questions 3–12, of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36),32 a self-report instrument. The questions in this subscale ask the subject to identify the degree to which physical health limits participation in high-effort, moderate-effort, and low-effort daily activities. The scores were transformed to a scaled score from 0–100 as per the SF-36 manual.33 Lower scores represent more functional disability. In this report, the three measures of functional disability will be referred to as instrumental, basic, and broad, respectively. Three dimensions of social support were assessed: frequency of social interaction with others, level of perceived satisfaction with others, and amount of instrumental help from others. These dimensions were measured by the corresponding three subscales of the Duke Social Support Index (DSSI).34 The analyses used multiple-regression techniques to determine independent associations between predictor and dependent variables. Poisson (log-linear) regression was used, with an adjustment for extraPoisson variation, because two dependent variables, instrumental and basic disability, were discrete, with skewed distributions. Parameter estimates (coefficients and standard error [SE]) are reported for the independent variables of interest; for patients with a depression diagnosis, the reference group (i.e., coefficient⳱0) was the nondepressed group. Two-tailed p-values were used, establishing a more conservative level of significance, given the large number of tests performed, and alpha was set at 0.05. Multicollinearity was not a problem in these analyses because a correlation matrix among the independent variables showed all correlations to be ⬍0.38. Age, gender, and medical illness burden (Cumulative Illness Rating Scale [CIRS])35 were covaried in all analyses. Baseline
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functional disability was controlled for in all longitudinal analyses. All analyses were performed both cross-sectionally (examining the relationship among variables at study intake) and longitudinally (examining the relationships between intake variables and 1-year functional outcomes). The first set of analyses examined the independent associations of social support and depression diagnosis with the functional measures. To examine social support’s moderator role, a multiplicative interaction term (depression diagnosis ⳯ social support) was then entered as the independent variable, also covarying the main-effects variables. The second set of analyses was similar, except that depressive symptoms, rather than depression diagnosis, were used.
RESULTS Table 1 shows the descriptive results. There were 305 subjects at intake, of which 31 had major depression; 19 had minor depression; and 255, no depression diagnosis. Of these, 247 completed 1-year assessments, 14 had died, and 44 refused or were not available for follow-up interviews. Compared with the living subjects who did not complete follow-up assessments,12 the 247 subjects who did so did not differ significantly on age, gender, or CIRS score, but had more education (mean [standard deviation {SD}]: 13.4 [2.8] years versus 12.2 [3.1] years; t[55.8]⳱ –2.5; p⳱0.02). At follow-up, 22 subjects had major depression, 14 had minor depression, and 211 no depression diagnosis. We first report the analyses examining the independent associations of depression diagnosis and social support with functional disability (Hypothesis #1), beginning with instrumental disability. Two of the three dimensions of social support (less social interaction and more instrumental help) were associated with more instrumental disability (coefficient [SE] for less social interaction: –0.20 [0.07];F[1, 294]⳱ 7.21; p⳱0.008; and for more instrumental help: –0.17 [0.06]; F[1, 294]⳱9.87; p⳱0.002). Depression diagnosis was not independently associated with instrumental or basic disability. No type of social support was associated with basic disability. Depression diagnosis was also not associated with broad disability, but two of the three dimensions of social support were
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Social Support, Depression, and Disability (perceived satisfaction: coefficient [SE]: 1.48 [0.75]; F[1, 294]⳱3.93; p⳱0.048; and instrumental help: 1.49 [0.73], F[1, 294]⳱4.21; p⳱0.041). In longitudinal analyses, depression diagnosis was not associated with any type of functional disability, nor was any dimension of social support independently associated with instrumental or broad disability. Less social interaction was independently associated with basic disability (coefficient [SE]: –0.15 [0.07]; F[1, 238]⳱4.86; p⳱0.029). To test the moderator effects as stated in Hypothesis #2, we examined the independent association of interaction terms (i.e., depression diagnosis ⳯ each social support subscale) with each functional measure. We first report the cross-sectional results. The interaction of depression diagnosis and social interaction was not independently associated with any type of functional disability. The interaction of depression diagnosis and more perceived satisfaction was not independently associated with instrumental or basic disability, but was associated with more broad disability (coefficient [SE] for major depression: –4.51 [1.57]; for minor depression: –6.47 [4.23]; F[1, 292]⳱ 4.91; p⳱0.008). The interaction of depression diagnosis and more instrumental help was not independently associated with instrumental disability, but was significantly associated with both basic disability (coefficient [SE] for major depression, –0.22 [0.09]; for minor depression, –0.59 [0.23]; F[1, 292]⳱6.58; p⳱0.002) and broad disability (coefficient [SE] for major depression, 4.05 [1.77]; for minor depression,
TABLE 1.
4.55 [3.08]; F[1, 292]⳱3.39; p⳱0.035). In the longitudinal analyses of moderator effects, none of the depression diagnosis–social support interaction terms were independently associated with functional outcomes. We now turn to the analyses examining the independent associations of depressive symptoms and social support with functional disability (Hypothesis #1), beginning with instrumental disability. Two of the three dimensions of social support (less social interaction and more instrumental help) were associated with more instrumental disability (coefficient [SE] for social interaction: –0.18 [0.07]; F[1, 295]⳱6.45; p⳱0.012; instrumental help: –0.14 [0.05]; F[1, 295]⳱ 6.81; p⳱0.010). Having more depressive symptoms was associated with having more instrumental disability (coefficient [SE]: 0.04 [0.01]; F[1, 295]⳱10.17; p⳱0.002); more basic disability (coefficient [SE]: 0.04 [0.01]; F[1, 295]⳱8.45; p⳱0.004), and more broad disability (coefficient [SE]: –1.04 [0.25]; F[1, 295]⳱17.38; p⳱⬍0.000). Social support was not associated with basic or broad disability. In longitudinal analyses, depressive symptoms and social support were not associated with instrumental or broad disability. Social support (less social interaction) was associated with basic disability (coefficient [SE]: –0.14 [SE] 0.07; F[1, 239]⳱3.92; p⳱0.049). In moderator analyses (Hypothesis #2): No depressive symptoms–social support interaction terms were associated with instrumental or basic disability, but the interaction of depressive symptoms and more perceived satisfaction was associated with broad dis-
Descriptive results, mean (standard deviation)
Variable
At Intake (Nⴔ305; 183 [60%] Women)
One-Year Follow-Up (Nⴔ247; 145 [59%] Women)
Age, years CIRS IADL PSMS PHYFXN Ham-D DSSI-SOC DSSI-PSS DSSI-IS
71.3 (7.6); range: 60–94 6.2 (3.0); range: 0–16 2.3 (4.5); range: 0–20 1.0 (1.8); range: 0–15 56.8 (29.7); range: 0–100 8.6 (6.8); range: 0–34 8.9 (1.4); range: 5–12 19.3 (2.4); range: 8–21 14.9 (2.3); range: 12–24
71.1 (7.5); range: 60–94 6.8 (3.0); range: 1–17 2.3 (4.4); range: 0–24 1.1 (2.1); range: 0–15 58.1 (29.5); range: 0–100 7.3 (5.7); range: 0–30 8.8 (1.5); range: 5–12 19.3 (2.3); range: 8–21 15.3 (2.2); range: 12–24
Note: Values are mean (standard deviation). CIRS: Cumulative Illness Rating Scale; Ham-D: Hamilton Rating Scale for Depression; IADL: Instrumental Activities of Daily Living; PSMS: Physical Self-Maintenance Scale; PHYFXN: Physical Functioning subscale from Medical Outcomes Study–Short Form-36; DSSI-SOC: Duke Social Support Inventory–Social Interaction Subscale; DSSI-PSS: Duke Social Support Inventory–Perceived Satisfaction Subscale; DSSI-IS: Duke Social Support Inventory–Instrumental Help Subscale.
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Travis et al. ability (coefficient [SE]: –0.24 [0.09]; F[1, 294]⳱6.70; p⳱0.010). In longitudinal analyses, no interaction terms were significant.
CONCLUSIONS Our first hypothesis was partially confirmed; depressive symptoms and all dimensions of social support were independently associated with more functional disability, although the specifics of these relationships varied among types of social support and functional disability. Our second hypothesis was also partially confirmed; social support (more instrumental help, more perceived satisfaction) was a moderator in a few depression diagnosis–functional disability crosssectional associations. Overall, our results underscore the call for functional disability to be investigated through the use of instruments assessing instrumental, basic, and broad aspects of functional disability, through self-rated and examiner-rated methods, and at cross-sectional and longitudinal time-points.7,36 Our study is also unique in demonstrating the complex relationships among depression, social support, and multiple types of functional disability within a primary-care sample. Older patients in primary care are characterized by heterogeneity in physical and emotional functioning, and this heterogeneity is at once a unique feature and a drawback for investigators. We do note here that our subjects’ overall instrumental and basic disability at baseline and follow-up were comparable to that found in community residents,37 rather than in psychiatric patients.24 The inclusion of dimensional and categorical assessments of depression, however, highlighted important distinctions across hypotheses between depressive symptoms and depression diagnosis. For example, significant moderator results were obtained primarily in analyses using depression diagnosis; these results are in keeping with another study examining social support as moderator in a sample of more severely depressed and disabled elderly patients drawn from a psychiatric setting.24 In sum, it is crucial to use an integrative framework that addresses both the heterogeneity of phenomena across the sample as well as the homogeneity of phenomena for specified sample subgroups in older adult primary care studies.
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Closer examination of results from each of the three dimensions of social support highlights the important and varied roles of social support in association with different types of functional disability. Our most uniform finding was the association of more instrumental help with all types of functional disability. Main effects for more instrumental help were associated with more instrumental disability across analyses of depressive symptoms and diagnoses. However, although instrumental help moderated the association between depression diagnosis and both basic and broad disability, instrumental help did not moderate any of the depressive symptom–functional disability associations. Variation in the moderating roles for instrumental help point to the need for researchers to further specify how and when receiving help from others may directly or indirectly affect different types of functional disability, with particular attention to potentially distinct interactions with depression diagnoses versus depressive symptoms. Regarding frequency of interaction, less social interaction was associated with more instrumental disability across analyses of both depressive symptoms and diagnoses. This result is consistent with previous findings in a psychiatric setting2 and further underscores the potent social and environmental features imbedded in instrumental functioning.31 However, unlike that cross-sectional study,2 we consistency found that less social interaction was associated with greater basic disability at 1 year. Leisure, social, or other discretionary activities may be among the first to show decline38,39 and thereby signal a temporary or long-term change in functional status. Indeed, low frequency of contact with others has been identified as an independent risk factor for functional disability in those with2,24 and without10 a depression diagnosis. Thus, it may be helpful for health care providers to ask older patients about changes in the frequency of social interactions. However, providers need to remain cognizant that changes in the frequency of social interactions may be adaptive, given the desire to conserve resources, and thus may not reflect a poorer quality of interactions.38,40 In contrast to other social-support studies with elderly subjects,2,24,25 less perceived satisfaction was not associated with instrumental or basic disability, although it was independently associated with broad disability, the one measure of self-rated functional disability in our study. Also, the interaction of de-
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Social Support, Depression, and Disability pression diagnosis and more perceived satisfaction was associated with broad disability. Because more perceived satisfaction has been independently associated with less functional disability in elderly patients with major depression in a naturalistic treatment study24 and with decreases in depression in a treatment study of primary-care elderly patients,27 our findings merit comment. Perhaps those depressed older patients who enter treatment studies are less satisfied with their social network and thereby represent a different population than those primary care patients in our naturalistic study. It is also possible that older adults proactively adapt and manage functional and emotional disability through having more satisfaction with others involved in their social network.38,40 Our results must be considered in the context of other study limitations. Our study group was largely “young-old,” predominantly white, and relatively well educated for an older cohort: these findings may not generalize to other populations. Also, we did not collect data about several other dimensions of social support, such as negative as well as positive interactions,41 providing as well as receiving support,42 or the distinctions between support from family members or friends.43 In summary, social support has important and varied roles in relation to functional disability and the depression–functional disability dynamic. Our findings contribute to knowledge of this area through the
use of multiple functional disability measures, as well as categorical and dimensional measures of depression in a heterogeneous primary-care group. Future research is needed to specify the complex relationships among depression, social support, and functional disability, cross-sectionally and over longerterm follow-up periods. Most importantly, striving to understand ways to slow the progression of functional disability is a goal with significant clinical and public-health implications.7,10,11 This work was presented in part at the Annual Meeting of the American Association for Geriatric Psychiatry, San Francisco, CA, February 25, 2001, and the Gerontological Society of America, Chicago, IL, November 15, 2001. The authors thank T.K. Noel, C. Doane, A. Wisner, A. Gleason, G. Kiernan, H. Stiner, and Z. Yoediono for technical assistance, and the patients and staff of the offices of Drs. J. Allen, M. Bergin, M. Berliant, C. Conners, R. Greene, M. Labanowski, R. Maggio, B. Peyser, and R. Pincus, and the Family Medicine Center at Highland Hospital. We thank the URMC Department of Biostatistics and Computational Biology research associate Shirley Eberly, M.S., and programmer Carrie Irvine, B.S., for their assistance in preparation of this manuscript. This work was supported by National Institute of Mental Health, grants K07-MH01113 (Dr. Lyness) and T32 MH18911 (E.D. Caine, M.D., PI).
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