depressive symptoms in relation to physical health

Vol. 124, No.3

AMERICAN JOURNAL OF EPIDEMIOLOGY

Copyright © 1986 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved

Printed in U.S.A.

DEPRESSIVE SYMPTOMS IN RELATION TO PHYSICAL HEALTH AND FUNCTIONING IN THE ELDERLY LISA F. BERKMAN,' CATHY S. BERKMAN/ STANISLAV KASL,' DANIEL H. FREEMAN, JR.,' LINDA LEO,' ADRIAN M. OSTFELD,' JOAN CORNONI-HUNTLEY,3 AND JACOB A. BRODY'

Berkman, L. F. (Yale School of Medicine, New Haven, CT 06510), C. S. Berkman, S. Kasl, D. H. Freeman, Jr., L. Leo, A. M. Ostfeld, J. Cornoni-Huntley, and J. A. Brody. Depressive symptoms in relation to physical health and functioning in the elderly. Am J Epidemio/1986;124:372-88. The associations between depressive symptoms and functional disability and chronic conditions are examined in an elderly cohort of 2,806 noninstitutionalized men and women living in New Haven, Connecticut who were interviewed in 1982 as a part of the Yale Health and Aging Project. The aim is to explore several potential sources of invalidity in using the Center for Epidemiologic StudiesDepression scale (CES-D) to measure depressive symptoms in elderly populations. In particular, the authors are concerned with the possibility that prevalent physical illnesses and disabilities may cause the older person to report many somatic complaints, a major component of most measures of depressive symptomatology, and thereby inflate his or her CES-D score. Mean CES-D scores are 4.86 for those without any disabilities and ·range to 13.51 for those with major functional disabilities. However, physical disabiiity is significantly associated with virtually every item on the CES-D scale not just those somatically-oriented items. The addition of functional disability to a multivariate model including age substantially weakens the associations between age and depressive symptoms. A factor analysis of responses from this elderly sample produces results almost identical to those reported by earlier investigators who studied younger and middle-aged adults. The authors conclude that physical disabilities among the elderly do not appear to be a major threat to the validity of the CES-D scale and that the strong associations between physical and mental health should be rigorously investigated. aged; chronic disease; depression; geriatrics; health surveys

Many questions have been raised concerning the validity of assessing depressive symptoms among the elderly using the same criteria and/or measures that are ap-

plied to younger populations. The association between age and symptoms of depres-sion, while frequently examined, is not well understood; and studies have produced con-

Received for publication June 27, 1985 and in final form February 7, 1986. Abbreviations: CES-D scale, Center for Epidemiologic Studies-Depression scale; DSM-111, Diagnostic and Statistical Manual, 3rd edition; NHANES-I, National Health and Nutrition Examination Survey. 1 Department of Epidemiology and Public Health, Yale University School of Medicine, P.O. Box 3333, 60 College St., New Haven, CT 06510. (Send reprint requests to Dr. Lisa F. Berkman at this address.) 2 Community and Family Medicine, Dartmouth Medical School, Hanover, NH.

3 Epidemiology, Demography and Biometry Branch, National Institute on Aging, Bethesda, MD. 4 School of Public Health, University of Illinois at Chicago, Chicago, IL. This paper is the result of National Institute on Aging (NIA) contract N01-AG-0-2105. Yale University is one of four sites funded by the Establishment of Populations for Epidemiologic Study of the Elderly. NIA project officer for these collaborative studies is Joan Cornoni-Huntley. The four sites funded under these contracts are the University of Iowa, Harvard University, Yale University, and Duke University.

372

DEPRESSIVE SYMPTOMS IN THE ELDERLY

flicting results. Most confusing have been the different reports showing variable rates of depressive symptoms among older people and generally lower rates of diagnosed depression, compared to younger and middleaged adults. Of particular concern is the possibility that physical ailments and problems common among older people might cause older people to report higher rates of somatic complaints, a major component on scales of depressive. symptoms. Thus, older people might score higher on scales of depressive symptomatology such as the Center for Epidemiologic Studies-Depression scale (CES-D) not because they actually have more dysphoria or feelings of depression, or sadness, but because their declining physical condition and perhaps the aging process itself increases their likelihood of reporting more problems with sleeplessness, loss of appetite, lassitude, problems concentrating, etc. If this were true, one might make a cogent argument that such somatic factors or realistic appraisals of their situations ought not to be considered a major part of a depressive mood or disorder in older populations. Another possibility is that clinicians may fail to make the diagnosis of depression in the older person because depressive symptoms are attributed to some obvious physical illness that may be present. The CES-D scale which we use in this study is a 20-item self-report scale designed to measure depressive symptomatology in the general population. Depressive symptomatology usually refers to the presence of dysphoria and somatic complaints that are often accompanied by associated features of depression, but do not necessarily meet the criteria for the clinical syndrome of depression. In the original development of the scale, items were selected for inclusion on the scale to represent the major symptoms in the clinical syndrome of depression as identified by clinical judgment, frequency of use in other questionnaires for depression, and factor analytic studies (1, 2). The items come from previously validated depression scales developed by sev-

373

eral different investigators (3-6). The components include depressed mood, feelings of guilt and worthlessness, fearfulness, helplessness and hopelessness, psychomotor retardation, loss of appetite, and sleep disturbance. In its usual manner of administration, the scale emphasizes current state or how the respondent felt in the past week. It is not designed to measure lifetime prevalence or duration of depressive symptoms. Nor is it similar to the Diagnostic and Statistical Manual, 3rd edition (DSMIII) criteria (7), which require that a certain number of symptom groups be represented within the individual. Perhaps most importantly a score on the CES-D scale does not reveal whether the symptom arises from a depressive disorder, a physical disorder, a drug, or a "realistic" appraisal of the individual's life situation. Thus, the scale taps a constellation of depressive symptoms that may not necessarily constitute a depressive disorder. Age trends for depressive symptomatology are conflicting and patterns are unclear. Several studies (8-10) have found that older people (65+ years) when compared to young people have lower rates of depressive symptoms. Other studies have found this pattern to be true for women but not for meri (11), who show a higher prevalence at older ages, or have observed a tendency for individuals in the oldest age groups (70+ years) to have higher rl).tes than persons in the younger age groups (12, 13). That results have been so inconsistent is not surprising, since studies have used different survey instruments and methods, different cut points for the same instrument, and relatively small samples of older people, especially of older people over age 70 years. The studies define "older" in different ways, and samples and cohorts have been substantially different. Thus, differences in prevalence rates may stem primarily from methodological problems and may not reflect real differences (13). Among the investigators who have studied depression in the elderly, several have expressed the concern that many individual

374

BERKMAN ET AL.

items on scales of depressed mood may reflect, to a large extent, the influence of physical disabilities or relatively realistic appraisals of the older person's future and not depressive symptomatology per se. Blumenthal (14) suggests that modest or low correlations found among subscales of the Zung Self-Rating Depression Scale, whereby the somatic symptoms and optimism factors were found to be highly correlated with other factors on the Zung Scale in younger people but not in older people·, may well reflect symptomatology caused by alterations in physical health. Depressive symptoms can be caused by many physical conditions, or symptoms may represent the manifestations of those physical conditions. An example of the first instance is that someone's reaction to physical illness or decline in functional ability may be to become depressed, i.e., to feel sad, unhappy, fearful, not hopeful about the future, depressed, etc. In the latter instance, the physical illness causes one to have a hard time getting going, to have restless sleep, or poor appetite. In this case, the disability causes changes in one domain, the somatic, but not across several domains. It is this latter possibility that is particularly troublesome in research concerning the elderly because if responses to these somatic items cause older people to score within the range of"depressed," they may be inappropriately categorized. Therefore, the motivation for this analysis was: 1) To examine, in a sample of people all aged 65 years or over, the relationship of age to individual items on the CES-D scale to see if older people responded to a few items in the "depressed" range much more commonly than the young/old people in the sample. 2) To examine the relationship of physical health, particularly functional ability, to the entire CES-D scale as well as to individual items to see if physical health is related to only somatic symptoms or is related more generally to depressive mood. Furthermore, we are interested to see if functional ability accounts for any observed association be-

tween age and depressive mood. 3) To analyze the underlying factors in the CES-D scale to see if, in an older population-based sample, similar domains or factors are evident as have been found in other community studies of younger people. Overall, our aim is to explore several potential sources of invalidity in using the CES-D scale to measure depressive symptoms in an elderly population. MATERIALS AND METHODS

Establishment of populations for the Epidemiologic Study of the Elderly Program The Epidemiologic Study of the Elderly Program is a collaborative program initiated by The National Institute on Aging (15). The program consists of four epidemiologic cohort studies in four locations: New Haven, Connecticut; East Boston, Massachusetts; Washington and Iowa Counties, Iowa; and Durham, North Carolina. The aim of these studies is to assess the general level of physical and mental health in a community population of older individuals, specifically with regard to the prevalence and incidence of certain chronic conditions, functional ability, level of depressive symptomatology and cognitive impairment. Another goal is to determine which behaviors, socioenvironmental conditions, and biologic variables are predictive of future declines in health in these elderly populations, including incidence of morbid conditions, hospitalization, institutionalization, and mortality. The Yale Health and Aging Project: The community and elderly population in New Haven This paper is based on data from the New Haven-based Yale Health and Aging Project. The study is based on a probability sample of 2,806 noninstitutionalized men and women aged 65 years and older living in the city of New Haven, Connecticut in 1982. The elderly in New Haven live, for the

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DEPRESSIVE SYMPTOMS IN THE ELDERLY

most part, in three types of housing: 1) public elderly housing, which is age and income restricted; 2) private elderly housing, which is age restricted; and 3) houses and private apartments. The sampling frame includes a sample drawn from each of these three types of housing arrangements. The reason to over-sample the elderly housing units is that such living arrangements are a large and increasing source of housing for older people. In New Haven, about one sixth of all persons aged 65 years and over reside in such homogeneous, age-segregated housing. These numbers are likely to increase over the next decades, not only in New Haven, but in many parts of the United States. The predominance of elderly females over males, and the significant number of elderly residing in housing specifically designed for the elderly motivated the selection of the sampling frame and subsequent sample.

of households existing at that time when combined with a concurrent listing for bulk meters. The sampling was done by dividing this list into segments or clusters of 12 housing units. The sample was drawn by selecting every 62nd unit and then screening the next 12 units for an eligible respondent. It was also decided to have equal numbers of men and women in the sample; therefore, all men enumerated were selected compared to a sampling ratio 1 in 1.5 women. The subsampling of women was performed using computer-generated Kish selection procedures (16). By this procedure, 8, 700 addressess were selected. An additional 57 housing units were identified by re-listing procedures. Of the 8,757, 7,878 were found to be occupied, eligible housing units, and, of these units, 99 per cent were enumerated. This enumeration and screening process yielded 1,577 eligible men and women, of whom 79 per cent of men and 76 per cent of women agreed to participate, for a total of 1,214 respondents, or 595 men and 619 women. 2) Public housing for the elderly. In all public housing for the elderly in New Haven, 1,058 households were identified as potentially yielding a person aged 65 or over. Of these, 1,002 were found to be occupied. Sin.ce the Yale Health and Aging Project was interested in obtaining as many older people living in public housing as possible, it was decided to census those

The sample The sample is divided into three housing strata which will be described individually. The number of respondents by age and sex for each of the three housing strata are shown in table 1. 1) The community stratum. The sample frame for the community portion of the sample was a utilities listing drawn in 1979 and shown to be a virtually complete listing

TABLE 1

Per cent distribution of study sample on age, sex, and housing stratum. Yale Health and Aging Project, 1982_ (unweighted data) (n = 2,806) Housing stratum Sex and age group (years)

Community stratum

Private housing for elderly

Public housing for elderly

Total

% in age group

n

age group

n

% in age group

n

% in age group

n

Men 65- 74 75+

62.69 37.31

373 222

53.17 46.83

176 155

55.23 44.77

132 107

58.45 41.55

681 484

Women 65- 74 75+

59.29 40.71

367 252

51.49 48.51

276 260

48.77 51.23

237 249

53.63 46.37

880 761

% in

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BERKMAN ET AL.

eligible households and include everyone eligible in the sample. The enumeration rate in the public housing s'tratum was virtually complete. Response rates were 89.5 per cent for men and 89.2 per cent for women, yielding a combined total of 725 respondents in the public housing stratum, or 239 men and 486 women. 3) Private housing for the elderly. In private elderly housing, 1,742 units were identified, of which 1, 700 were occupied. Of these, 99 per cent were enumerated. Estimates of the number of men and women living in private housing suggested that 24 per cent of the elderly persons in these units would be male. Therefore, it was decided to interview all elderly men in the sample but only 1 in 2.5 women, so that there would be equal numbers of men and women sampled from private housing. The sub-sampling of females was performed as it had been in the community stratum, using computer-generated Kish selection procedures (16). In both public and private housing, units included in another survey were excluded from the sample, resulting in a loss of 12.9 per cent of units from these two strata. Response rates for private housing were 82 per cent for men and 84 per cent for women, giving a combined total of 867 respondents, or 331 males and 536 females. Interview schedule: items and scoring techniques

The interview schedule is a 75-page structured interview which takes just over an hour to complete. All interviews are done with an interviewer reading questions and response categories to the respondent. Only those items used in analyses in this paper will be described. CES-D. The 20 CES-D items were scored on a standard four-point scale (0- 3) with a cut point of ~16 used to distinguish those with a sufficient amount of depressive symptomatology so that they closely resemble depressed patients in treatment. The potent ial range of the scale is 0 to 60; our actual range was 0 to 57. The cut point of

16 has been found to be the most valid cut point based on tests with clinical populations. Scoring for positively worded items (4, 8, 12, 16) has been reversed so that high scores represent responses in the depressed range. Of the 2,806 respondents, the vast majority responded to all 20 items. Only 79 did not answer any, and, of the remainder, 2,697 answered 17 or more. In analyses which follow, those who failed to answer at least 17 items (n = 109) were excluded. Most of these respondents were unable to complete most parts of the interview and the questionnaire was responded to by a proxy. CES-D scores for those with three or fewer missing items were created by obtaining mean scores based on the number answered and multiplying by 20. The alpha coefficient in our sample was 0.86. Health. Functional ability is measured by a Guttman scale of current need for help with 15 common activities. It is constructed in a way that is similar but not identical to a cumulative disability index developed for the Framingham Disability Study (17-19). The scale is composed of three subscales: 1) a Basic Activities of Living Scale based on seven items drawn from Katz's activities of daily living scale (20), 2) a three-item scale of gross-mobility function developed from the work of Rosow and Breslau (21), and 3) a physical performance scale based ~m five items from Nagi (22). The Index of Functional Disability is a Guttman scale ranging from 0- 4, in which 0 equals nondisability in all three subscales, 1 equals disability in the Nagi scale only, 2 equals disability in the Rosow-Breslau scale, 3 equals disability in both the Rosow-Breslau and Nagi scale but not on the Katz activities of daily living scale, and 4 equals disability on all three subscales. The coefficient of reproducibility is 0.95, and the coefficient of scalability is 0.84. Of 2,786 respondents on whom information was available to scale the 15 items, 48 people were excluded because they did not fit the scale patterns. All of these people were scored as disabled on the Katz activities of daily living scale but not on both other subscales.

Chronic c asking respc told them th conditions: l abetes, cirrh fractures, h Parkinson d cause hypert group, we lo• ually. All re and a scale" Cognitive ing the PfeiJ instrument ~ farb Short I (23). In our "What is the is your addr( ate for com Our 10-item more incorr( impairment. which result fusal were s, baum (24) fo Sociodemo status, years race, religion private, or ot in the preser Analysis. ~ by housing t censused an women were weights have to adjust f< sponse, and data allow us larger define• Haven. Pre' standard errc sample desig ing differenct an estimate ' count the C< ployed in thi In order t< tween age, se individual CI a series of 20

DEPRESSIVE SYMPTOMS IN THE ELDERLY

377

Chronic conditions were measured by item as the dependent variable. Statistical a king respondents whether a doctor ever tests for these analyses incorporate estitold them they had ~my of the 11 following mates of design effects utilizing Taylor seconditions: heart attack, stroke, cancer, di- ries linearization procedures (26, 27). As abetes, cirrhosis, broken hip, or any other noted by Shaw and LaVange (26), among fractures, high blood pressure, arthritis, others, these tests are appropriate for large Parkinson disease, or an amputation. Be- samples such as ours. A factor analysis is presented with uncau e hypertension was so common in this group, we looked at this condition individ- weighted data since it was determined that ually. All remaining items were summed, results were not substantially different from the results with weighted data. Factor and a scale was created. Cognitive impairment was measured us- analyses were performed initially on the ing the Pfeiffer Scale, a 10-item screening sample by conducting separate analyses by instrument similar to the Kahn and Gold- age and by sex. With few exceptions, the farb Short Portable Mental Status Exam sex and age analyses were all very similar. (23). In our scale, we changed one item, Thus, the results for the entire sample are 'What is the name of this place?'' to "What presented with a discussion of age- and sexis your address?" since it seemed appropri- specific findings when appropriate. Findate for community-dwelling respondents. ings are presented for an orthogonal (V AROur 10-item scale was scored with eight or IMAX) rotation of a principal components more incorrect responses as indicative of analysis. impairment. For this scale, missing items RESULTS which resulted from the respondent's re- , The prevalence of depressive fu al were scored as incorrect (see Filensymptomatology baum (24) for a discussion of this issue). Figure 1 shows the per cent distribution Sociodemographic. Items on age, marital tatus, years of education, level of income, of CES-D score by sex. The distribution is race, religion, and housing stratum (public, skewed, with a large proportion of responprivate, or other community) were included dents scoring in the low range. General in the present analyses. response patterns are very similar for men Analysis. Since the sample was stratified and women, with the exception that women by housing type with some housing strata are somewhat more likely to score in the cen used and others sampled, and since "depress~d" range. The percentage of men women were further subsampled, sampling and women scoring ~16 is 11.31 and 19.21, \"eights have been assigned to respondents respectively. The me~n scores for men and to adjust for differential sampling, re- women, respectively, are 6. 72 and 8.82. -ponse, and coverage rates. The weighted Figure 2 shows the mean CES-D scores data allow us then to draw inferences to the by age and sex. Age is divided into five-year larger defined population of elderly in New age groups. Men show a steady increase in Haven. Prevalence rates and associated prevalence of depressive symptoms with tandard errors are based on the underlying age, while the pattern for women reveals a ample design. Tests of significance assess- peak in the 75-79 years age group. In this ing differences in these rates were based on sample, women have higher prevalence an estimate of variance that took into ac- rates than men of comparable ages until count the complex sampling design em- age 85 years, when men have higher scores. ployed in this study (25). Depression scores vary dramatically by In order to explore the associations be- sociodemographic and health characteristween age, sex, functional ability, and each tics of older men and women. Table 2 shows individual CES-D scale item, we conducted the bivariate relationships of CES-D score a eries of 20 multiple regressions with each with selected variables both in terms of

378

BERKMAN ET AL.

22 t

20

18

16

f

R E

14

Q

u

E 12 N

c y

p 10

E R

c

E N B

T

6

4

2

0 0

5

10

15

20

25

30

35

40

45

so

55

60

CES-0 SCORE LEGEND: SEX

e-e-e HRLE

+-+--• FEHRLE

Per cent distribution of Center for Epidemiologic Studies-Depression (CES-D) scale scores by sex. Yale Health and Aging Project, 1982 (weighted data). FIGURE 1.

mean scores and percentage scoring ~16. In interpreting differences in means and associated standard errors, the reader should keep in mind the skewed distribution of responses shown in figure 1. In our sample, differences due to income and education were greater than racial differences. Persons who had a total family income of less than $5,000 had mean CES-

D scale scores of 9.86, compared to 5.76 for those with family incomes of $10,000 or more per year. Education shows similar though not as dramatic trends, with mean scores ranging from 8. 77 for persons with less than a high school education to 6.11 for those with some college or more. It is important to consider the association of the CES-D scale with physical

379

DEPRESSIVE SYMPTOMS IN THE ELDERLY

55 54 53

52 51 50 49 48 47 46 45 H

43

42 41 40 39 38 37 36 35

H 34 E 33 A 32 N 31

c s

30 29

E 28

27

- 26 0 25 24

s c

23

22 0 21

R 20 E 19

18 17

16

15 14 13

12 11-j 10-j 9

8 7 6 5 4 3

... ----------- -.-------------._ ___ -----

2 1

0~~~~~~~~~~~~~~~~~~~~~~~~~~~ 90+ 85-89 75-79 80-84 65-69 70-74 AGE GROUP LEGEND: SEX

~

HALE

+-,.._...,

FEHALE

FIGURE 2 . Mean Center for Epidemiologic Studies-Depression (CES-D) scale scores by age group and by sex. Yale Health and Aging Project, 1982 (weighted data).

health since depression has been hypothesized to be both the cause and consequence of poor health. Of particular concern to us is a third possibility-that the CES-D scale of symptoms is simply tapping health status per se. Persons with major functional disabilities have substantially higher mean CES-D scores than individuals without any disabilities (13.51 vs. 4.86). However, it is

evident that persons who report a disability only on the Nagi scale (group 1) have higher mean scores, and a greater percentage of these individuals score above the cut-point of 2:16 than do persons who report a disability only on the Rosow-Breslau scale (group 2). This finding may either indicate that the score as constructed does not perfectly reflect the severity of disability or

380

BERKMAN ET AL. TABLE 2

Mean Center for Epidemiologic Studies-Depression (CES-D) scale scores and standard errors by selected ~characteristic. Yale Health and Aging Project, 1982 (weighted data) Characteristic Total Sex* Men Women Age group (years)* 65-74 75+ Race White Nonwhite Income* $0- 4,999 $5,000- 6,999 $7,000- 9,999 $10,000+ Education*