Compared to respondents who were included in our analysis sample (n=2406), those who were not (n=669) were significantly older (t=2.98, df=3073, p<0.01), less likely to be white (chi-square=48.20, df=1, p<0.01), less likely to be married (chi-square= 9.84, df=2, p<0.01), less likely to try to change their weight (chi-square=25.47, df=1, p<0.01), more likely to have ever smoked (chi-square=30.90, df=2, p<0.01), and had significantly higher CES-D scores (t=3.88, df=3047, p<0.01) (). also shows that 4.4% of the persons in the analysis sample had depressed mood at T1 and 9.5% had depressed mood at T4. Also, 70.7% of the persons in the analysis sample remained weight stable over the 3-year period, while 18.1% lost weight and 11.2% gained weight over the 3-year period. Finally, 34.8% of the persons in the analysis sample reported interim hospitalization and 28.3% reported incident mobility limitation.
Main characteristics of the study population
shows that people with depressed mood at T1 were more likely to develop mobility limitations (chi-square=25.60, df=1, p<0.01). People who were weight stable were least likely to have hospitalizations (chi-square=27.33, df=4, p<0.01) and mobility limitations (chi-square=28.98, df=2, p<0.01). The weight loss and gain group did not significantly differ from each other regarding the number of hospitalization and mobility limitation. People with hospitalizations were less likely to be weight stable over 3 years (chi-square=27.23, df=4, p<0.01) and more likely to have depressed mood at T4 (chi-square=11.26, df=2, p<0.01) (). All three hospitalization categories differed significantly from each other regarding the distribution over the weight change groups. People with one or two hospitalizations did not differ significantly from those without or 3 or more hospitalizations regarding the prevalence of depressed mood at T4. Further, people with mobility limitations were less likely to be weight stable (chi-square=28.98, df=2, p<0.01) and more likely to have depressed mood at T4 (chi-square=62.02, df=1, p<0.01).
The results of the multinomial logistic regression analyses demonstrating the effect of T1 depressed mood on 3-year weight change are presented in . Persons with T1 depressed mood had an increased risk of 1.91 (Wald=5.78, df=1, p=0.02, 95% confidence interval (CI):1.13–3.22) to have a weight gain of ≥5% over the 3-year period, compared to those with T1 depressed mood with no weight change (Model 1), adjusted for baseline weight and other covariates. Compared to the relative risk from Model 1, the OR in Model 2 decreased 16% to 1.76 (Wald=4.31, df=1, p=0.04, 95%CI:1.03–3.00) when both interim hospitalization and incident mobility limitation between T1 and T4 were entered in the logistic regression analyses.
Effect of T1 depressed mood on 3-year weight change a
presents results from multivariate logistic regression analyses demonstrating the effect of 3-year weight change on T4 depressed mood. Persons who showed a weight loss of ≥5% over the 3-year period had a significantly increased risk of depressed mood at T4 (Wald=4.95, df=1, p=0.03, OR:1.51; 95%CI:1.05–2.16) compared to those with no weight change over the 3-year period (Model 1), adjusted for T1 BMI, T1 depressed mood, and other covariates. Compared to the relative risk from Model 1, the OR decreased 27% to 1.37 (Wald=2.89, df=1, p=0.09, 95%CI:0.95–1.98) when both interim hospitalization and incident mobility limitation between T1 and T4 were additionally entered in the logistic regression analyses (Model 2). When we excluded participant with depressed mood at T1, results remained very similar (data not shown)
Effect of 3-year weight change on T4 depressed mood a
In additional analysis, we examined the large group of weight stable people and defined ‘true’ weight stable people as people who did not gain or lose more than 5% of their baseline weight at every follow-up measurement (including T2, T3, and T4). Eighty-three percent of the weight stable group was truly weight stable. Those who gained or lost more than 5% of their weight but were considered weight stable based on their T4 weight were not at higher risk of depressed mood than the truly weight stable people (data not shown).
Depressive symptoms were measured with the full 20-item CES-D scale. A number of these items capture somatic symptoms which could be associated with body weight or change therein. Therefore, we performed a sensitivity analysis where we excluded the somatic items in calculation the CES-D score. The reciprocal associations between depressed mood and weight change remained very similar with this new CES-D score (data not shown).