Cross-sectional and Prospective Study of Exercise and Depressed Mood in the Elderly
The Rancho Bernardo Study
Donna Kritz-Silverstein,
Elizabeth Barrett-Connor and
Catherine Corbeau
From the Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA.
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ABSTRACT
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This study examined cross-sectional and prospective associations of exercise with depressed mood in a community-based sample of older men and women (aged 5089 years in 19841987) in southern California. Regular strenuous exercise and exercise
3 times per week were reported; depressed mood was assessed by using the Beck Depression Inventory (BDI). After exclusion of persons with categorical depression and those rating themselves largely or extremely physically limited during the previous month, data on 932 men and 1,097 women were available for cross-sectional analysis. Exercise and depressed mood were reassessed for 404 men and 540 women in 19921995; these data were the focus of prospective analyses. In 19841987, exercise rates were high (>80%), and average BDI scores were low. Cross-sectional analyses indicated that before and after adjustment for covariates, exercise was significantly associated with less depressed mood. However, prospective analyses of the 944 persons who attended both clinic visits indicated no association between baseline exercise and either follow-up BDI score (p > 0.10) or change in BDI score between baseline and follow-up (p > 0.10). Results confirm that exercisers have less depressed mood. However, exercise does not protect against future depressed mood for those not clinically depressed at baseline.
aged; depression; exercise; prospective studies
Abbreviations:
BDI, Beck Depression Inventory; NHANES I, First National Health and Nutrition Examination Survey; SD, standard deviation.
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INTRODUCTION
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The beneficial effects of exercise in the elderly are well documented and include reductions in morbidity and mortality (1
3
). It has also been proposed that physical activity can improve mental health status, particularly depression. Although the exact mechanism for the alleged antidepressant effect of exercise is still unknown, several psychological and physiologic mechanisms have been proposed, including increased feelings of self-efficacy, self-perceptions of control and mastery, reduced physiologic responses to stress, and beneficial effects on neurotransmitters such as increased serotonin and endorphins (4
).
Several studies have reported a therapeutic effect of exercise on depression, including for the moderately depressed elderly (5



10
). Recently, Blumenthal et al. (11
) reported that 16 weeks of treatment with aerobic exercise was equally as effective as antidepressants for treatment of major depressive disorder in older men and women. An immediate improvement in mood with exercise has also been reported (3
, 12


16
). King et al. (17
) and Martinsen et al. (18
, 19
) concluded that only moderate activity was necessary to attain psychological benefits.
Cross-sectional, population-based studies have shown an inverse association between exercise and depression scores (20







29
), but it is unclear whether the beneficial effects of physical activity on mood persist over time. Prospective studies of exercise and depression have yielded inconsistent findings (5
, 20
, 22
, 27
, 28
, 30
32
). For example, the Alameda County Study (27
), the First National Health and Nutrition Examination Survey (NHANES I) (30
) follow-up study, and the Paffenbarger et al. study (31
) reported that a low level of physical activity was related to the risk of depression. Others have reported that clinically depressed women who increased their physical activity had a more favorable 5-year prognosis (22
) and that exercise training produced greater improvements in elderly men and women with concomitant emotional impairments (5
). In contrast, the Upper Bavarian Field Study (20
) found that a low level of physical activity was not a risk factor for later depression, and Lennox et al. (28
) found that exercise had no beneficial effect on the mood of nondepressed persons selected from a nonclinical population. Additionally, a recent study by Cooper-Patrick et al. (32
) of 973 physicians found no association between physical activity at midlife and the incidence of depression up to 15 years later.
Most of the previous prospective studies examined clinically depressed persons only (5
, 22
) or included both depressed and nondepressed persons in their samples (20
, 27
, 28
, 30
32
). Few if any previous studies considered social support or numbers of friends, which may be associated with less depressed mood, and few excluded physically limited persons. The latter limitation may have led to confounding, as both depression and physical limitation could reduce physical activity. Therefore, the purpose of the present study was to examine the cross-sectional and prospective association of exercise with depressed mood in a community-based sample of older men and women who were not clinically depressed or physically limited at baseline.
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MATERIALS AND METHODS
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Subjects
Subjects were White, middle-class men and women aged 5089 years who participated in the Rancho Bernardo Heart and Chronic Disease Study. Between 1972 and 1974, 82 percent of all adult residents of the southern California geographically defined community of Rancho Bernardo were enrolled in a study of heart disease risk factors. Surviving members of this cohort have been followed with periodic clinic evaluations. Between 1984 and 1987, 2,375 persons (1,055 men and 1,320 women) aged 50 years and older, representing approximately 81 percent of local surviving members of the original cohort, visited a clinic. Eight years later (19921995), 1,180 surviving members of this cohort also participated in an additional follow-up visit. All subjects who participated in both visits were ambulatory, and written informed consent was obtained.
At both the 19841987 and 19921995 clinic visits, a standardized interview was administered by a trained interviewer in a private room. During these interviews, participants were asked questions about their current marital status, cigarette smoking history (ever smoked, current smoking), alcohol consumption during the previous week, current or ever use of estrogen replacement therapy (women), and social support including participation in social groups, degree of involvement in each group, and number of close friends and relatives. Participants were also asked to rate their physical and emotional functioning during the previous month from the following choices: not limited at all, small amount of limitation, medium amount of limitation, large amount of limitation, or extremely limited. Regular strenuous exercise and exercise at least three times a week were assessed by asking the following questions: Do you regularly engage in strenuous exercise or hard physical labor? (no/yes), and Do you exercise or labor at least three times a week? (no/yes). Reported physical activity was validated indirectly by demonstrating a significant inverse correlation with pulse rate and by a positive correlation with high-density lipoprotein cholesterol levels (33
).
Height and weight were measured by using a stadiometer, with the participant wearing light clothing and no shoes. Body mass index, defined as weight (kg)/height (m)2, was used as an estimate of obesity.
At the 19841987 visit, depressed mood was assessed by using 18 of the 21 items on the Beck Depression Inventory (BDI) (34
, 35
). In accord with criteria described by Shrout and Yager (36
), 3 of the original 21 items (guilt, expectation of punishment, and self-hate) were excluded from the questionnaire in an effort to reduce the length of the scale without compromising its reliability in this population. Total scores were adjusted proportionally to correspond to scores and cutpoints established for the full 21-item scale by multiplying them by 21/18. At the 19921995 visit, the full 21-item BDI was administered. For the present analysis, only the 18 items administered at both visits were used to calculate BDI score. Reliability of the BDI, as assessed with Cronbach's alpha, was 0.73 for the 19841987 visit and 0.75 for the 19921995 visit, similar to the coefficients based on studies of other samples of elderly community volunteers (alpha = 0.76) and depressed outpatients (alpha = 0.73) (36
). Persons who scored below the cutpoint of 13 were considered not categorically depressed.
Of the 2,375 subjects who participated in the 19841987 visit, 2,248 (1,018 men and 1,230 women) completed the BDI. Because clinical depression and physical limitation can each preclude exercise (37
), the 68 categorically depressed persons (defined as BDI
13; n = 21 men and 47 women) as well as the 151 subjects (n = 65 men and 86 women) who rated themselves as largely or extremely physically limited during the month prior to the 19841987 visit were excluded, leaving 932 men and 1,097 women as the focus of the baseline cross-sectional analyses. Of the 1,180 subjects who participated in both the 19841987 and the 19921995 clinic visits, the 944 persons (404 men and 540 women) who completed the BDI at both visits were the focus of the prospective analyses.
Statistical analysis
All analyses were sex-specific. Age-adjusted cross-sectional comparisons of BDI scores by regular strenuous exercise (no/yes) and by exercise three or more times a week (no/yes) were made by using analysis of variance. Cross-sectional comparisons adjusted for age, body mass index, smoking, alcohol consumption, and marital status were performed with analysis of covariance.
For the prospective analyses, men and women were categorized by exercise status at the 19841987 clinic visit; BDI scores at the 19921995 visit served as the dependent variable. Analysis of covariance was used to compare BDI scores at the 19921995 visit by exercise status at the 19841987 visit after adjustment for age, body mass index, smoking, alcohol consumption, social support, and, for women, use of estrogen replacement therapy. Change in BDI score between the two visits, by exercise status in 19841987, was examined by using analysis of covariance to further assess longitudinal associations. Age-adjusted comparisons of those who did and did not participate in the 19921995 follow-up evaluation, by exercise and BDI scores in 19841987, were accomplished with the Mantel-Haenzel extension test and analysis of covariance. In addition, subjects were grouped into four categories according to their exercise status in 19841987 and 19921995: those who reported exercise at both visits, those who did not report exercise at either visit, and those who reported exercise at one visit but not the other. These four groups were compared on the basis of the 19921995 BDI scores by using analysis of variance and covariance. Finally, selection and response bias were assessed by using analysis of covariance to compare the BDI scores and the Mantel-Haenzel extension test to compare the exercise rates of subjects who participated in only the baseline 19841987 visit with those of subjects who participated in both visits.
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RESULTS
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The average age at the baseline (19841987) visit was 71 years (standard deviation (SD), 9.6; range, 5089) for men and 70 years (SD, 9.2; range, 5089) for women. Exercise at least three times per week was reported by 85 percent of the men and 81 percent of the women; 26 percent of the men and 21 percent of the women reported engaging in regular strenuous exercise (table 1). For this visit, mean BDI scores (which excluded subjects with categorical depression) were 4.3 for men and 4.8 for women. The mean age for the 944 who participated in both visits was 65.6 years (SD, 8.5; range, 5088) for men and 66.6 years (SD, 8.8; range, 5089) for women at baseline, and 73.8 years (SD, 8.6; range, 5895) for men and 74.9 years (SD, 8.9; range, 5896) for women at follow-up. Men and women who attended both clinic visits were significantly younger at baseline than those who attended only the baseline visit (F = 232.68 and F = 124.77, respectively; p < 0.001). At the 19921995 visit, mean BDI scores were 4.6 for men and 5.3 for women; 3 men and 14 women met the BDI criteria for categorical depression. Distributions of the covariates for men and women assessed at the 19841987 visit and the 19921995 visit are shown in table 1.
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TABLE 1. Distribution of depression, exercise, and other covariates measured for men and women at the 19841987 and 19921995 clinic visits, Rancho Bernardo Study
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For both men and women, BDI score was positively associated with age (p < 0.001). There was an inverse association between number of close friends and scores on the 19841987 BDI for both men and women (p < 0.001 and p < 0.01, respectively). Women who reported they had one special person with whom they felt close also tended to have lower BDI scores (p < 0.06). BDI scores did not vary by activity in groups or by marital status (p > 0.10). Similar associations were observed between social support and BDI scores assessed at the 19921995 visit.
Cross-sectional comparisons of depression scores by exercise status at the 19841987 visit are shown in table 2. After adjustment for age, both men and women who engaged in regular strenuous exercise had significantly lower BDI scores than men and women who did not (F = 9.85 and F = 8.16, respectively; p < 0.01). Exercise three or more times per week was also associated with significantly lower age-adjusted BDI scores for men (F = 5.51, p < 0.05) and women (F = 5.44, p < 0.05), and results were similar after adjustment for age, body mass index, smoking, alcohol consumption, social support, and estrogen use (in women). Similar patterns of results were obtained from cross-sectional comparisons of depression scores by exercise status at the 19921995 visit, but statistically significant differences in BDI scores were observed for regular strenuous exercise only, with the exception of exercise three or more times per week in the age-adjusted model for men (table 2).
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TABLE 2. Adjusted cross-sectional differences in depression scores, by exercise status, for men and women in the Rancho Bernardo Study, 19841987 and 19921995
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As shown in table 3, exercise status reported in 19841987 did not predict future depression scores at the 19921995 visit for men or women before or after adjustment for covariates (p > 0.10 for both regular exercise and exercise three or more times per week). Table 3 also shows that there were no significant differences in the change in BDI scores between the two visits by exercise status (either strenuous or three times per week) in 19841987 (p > 0.10).
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TABLE 3. Adjusted* prospective associations of depression scores in 19921995 with change in depression scores between visits, by exercise status in 19841987, for men and women in the Rancho Bernardo Study
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Comparisons of unadjusted and adjusted mean BDI scores at the 19921995 visit, after categorization of subjects by their exercise status at both visits, are given in table 4. As shown, in both the unadjusted and adjusted analyses, men who reported at both visits that they had engaged in regular strenuous exercise had the lowest BDI scores, followed by men who did not report engaging in regular strenuous exercise in 19841987 but did so in 19921995. Men who did not report at either visit that they had engaged in regular strenuous exercise had the highest BDI scores. A similar pattern of results was found for women but was statistically significant only in unadjusted analyses (p < 0.01) and was of borderline statistical significance in adjusted analyses (p < 0.10). No statistically significant differences were observed in 19921995 BDI scores after categorizing persons on the basis of reported exercise three or more times per week. However, the mean BDI scores followed a similar pattern; those not reporting exercise at either visit or only at the 19841987 visit had the highest BDI scores, and those reporting exercise at both visits or reporting no exercise at 19841987 but exercise at the 19921995 visit had the lowest BDI scores (table 4).
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TABLE 4. Unadjusted and adjusted comparisons§ of mean BDI¶ scores in 19921995 after categorization by exercise status at both visits, for men and women in the Rancho Bernardo Study
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The exercise and the depression scores in 19841987 were each examined as determinants of nonparticipation in the 19921995 evaluation. The 19841987 BDI scores of those who did not attend the follow-up visit were marginally higher than those of the subjects who attended both visits (4.7 vs. 4.4, p = 0.07). Also, as compared with those who attended only the baseline visit, greater proportions of those who attended both visits engaged in regular strenuous exercise (20.6 vs. 26.3 percent, p = 0.003) and exercised three or more times per week (80.8 vs. 85.7 percent, p = 0.003).
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DISCUSSION
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Most of this older cohort was physically active and had low BDI scores. Nevertheless, subjects who were more physically active had lower depression scores at baseline and at the second evaluation 8 years later. However, baseline exercise pattern did not predict BDI score 8 years later. The cross-sectional associations and lack of prospective associations were unchanged after adjustment for age, body mass index, smoking, alcohol consumption, social support, and estrogen replacement therapy (in women). Although the prevalence of exercise decreased between visits, the mean BDI scores were similar, providing further support for the lack of a causal association between exercise and depression. Lack of a long-term protective effect of exercise against depressed mood is shown by the finding that the BDI scores of persons who reported exercise at the earlier visit but not at the second evaluation were similar to those for persons who did not report exercise at either visit.
The cross-sectional results of the present study are in accord with previous studies showing a positive association between exercise and mood in older men and women (15
, 29
). Similarly, in accord with other studies, fewer older women than men reported strenuous or regular exercise (15
, 29
). Farmer et al. (30
) suggested that men and women differentially report physical activity because of cultural expectations and habits. Since many of the physical activity questionnaires used in epidemiologic studies were developed and validated primarily with men, Blair et al. (38
) reported that such questionnaires may not adequately reflect women's physical activities such as housework. In this analysis, we did not use leisure-time physical activity questionnaires, which target (primarily) male sports, or the newer instruments, which target housework, with largely unisex associations. NHANES I (30
) found that recreational physical activity independently predicted depressive symptoms, as assessed by the Center for Epidemiology Studies Depression Scale, an average of 8 years later in healthy White women aged 2577 years. Physical activity was assessed in NHANES I by using a single question with three levels (much exercise, moderate exercise, and little or no exercise), while the Rancho Bernardo study used two questions and dichotomous variables (no/yes) to represent regular exercise and exercising at least three times a week. Use of fewer categories may have attenuated associations in the Rancho Bernardo data, but these simple questions were associated with heart rate and high density lipoprotein cholesterol in the expected directions (33
). The adequacy of these questions in assessing physical activity is further demonstrated by the significant cross-sectional associations that were observed.
The prospective results of this study showing no exercise-mood association are in accord with those of Lennox et al. (28
), who reported no significant changes in mood after 13 weeks of a randomized clinical trial of exercise in a nondepressed population. Weyerer and Kupfer (25
) also found that a low level of physical activity reported at the baseline visit was not a risk factor for developing depression at follow-up. Furthermore, a study of physicians (32
) found that the incidence of depression 15 years later was similar for exercisers and nonexercisers, and becoming physically active over the 8-year follow-up period did not reduce the risk of depression relative to those who were inactive. Differences in the results of the prospective portion of the present study from those finding an exercise-mood association may reflect the older age of our cohort, their relatively low prevalence of depressed mood compared with other elderly cohorts (39
, 40
), or their higher frequency of reported exercise (13
).
Because depression could reduce exercise, the low rates of depressed mood at baseline and follow-up may reflect in part our exclusion of categorically depressed subjects at baseline. Survival bias, in which clinically depressed persons have a higher mortality rate, did not explain our results because subjects clinically depressed at baseline were excluded. Selection bias was observed, with a lower response rate for depressed subjects; 19841987 BDI scores of those persons who attended only the earlier visit were marginally higher than those of persons who attended both visits. Response bias, in which persons who participated in both visits were more likely to engage in physical activity, was also observed. However, response bias should have favored the observation of a longitudinal association. The exercise measures used in this study reflected relative intensity (or strenuousness) of exercise rather than absolute intensity. In a cohort of older persons such as the Rancho Bernardo study, moderate activity might be perceived as strenuous. Although this would mean that the cross-sectional associations of exercise with less depressed mood may be stronger than reported in the present study, it is unclear whether more intense exercise would be prospectively associated with less depressed mood.
Overall, the prevalence of depressed mood in this middle-class cohort was low, probably reflecting their relatively high socioeconomic status. Other studies have shown an inverse association of depression with socioeconomic status (41
, 42
). However, the middle-class socioeconomic status and relatively high educational level of this cohort means that the self-reported information was generally reliable. Previously published papers indicate that compared with national, representative samples of persons their age, those in the Rancho Bernardo cohort are on average somewhat leaner (43
), are no more or less likely to have been cigarette smokers (44
), and have similar levels of alcohol consumption, systolic blood pressure, diabetes, impaired glucose tolerance, and plasma total cholesterol (45



50
). Age may also be a confounder. Participants in the Rancho Bernardo cohort are older on average than those in most other cohort studies, but they have a lower prevalence of depression. It is possible that a prospective protective association might have been observed in a younger cohort with a wider range of exercise and depression scores.
In other studies, social support has also been shown to have an inverse association with depression (41
). In accord with this finding, the present study found an inverse association between number of close friends and BDI scores for both men and women, and women who reported having one special person with whom they felt close also had lower BDI scores. However, neither marital status nor activity in social groups was associated with BDI scores. Previous studies of women in this cohort have found estrogen use to be inversely associated (51
) and obesity to be positively associated (52
) with depressed mood, but adjustment for these covariates did not modify the observed associations.
In sum, the present study confirms other studies showing that exercise is cross-sectionally associated with less depressed mood among older persons. However, the present study also shows no long-term protective effect of exercise against depressed mood among those not clinically depressed at baseline. The absence of protection against future depressed mood is compatible with a cause-or-effect association. Either exercise leads to less depressed mood or depressed mood leads to less exercise. Clinical trials of ambulatory, community-dwelling older adults using exercise interventions of varying types, intensities, and durations with standardized schedules, along with assessment of mood before, during, and at the end of the study, will be necessary to sort out the direction of the association.
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ACKNOWLEDGMENTS
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This work was supported by grant DK31801 from the National Institute of Diabetes and Digestive and Kidney Diseases and grant AG07181 from the National Institute of Aging.
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NOTES
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Reprint requests to Dr. Elizabeth Barrett-Connor, Department of Family and Preventive Medicine, University of California San Diego, 9500 Gilman Drive, 0607, La Jolla, CA 92093-0607 (e-mail: ebarrettconnor{at}ucsd.edu).
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Received for publication February 28, 2000.
Accepted for publication June 19, 2000.