Body Mass Index, Blood Pressure, and Risk of Depression in the Elderly: A Marginal Structural Model

The authors' objective was to investigate the associations of body mass index (BMI; weight (kg)/height (m)(2)) and blood pressure with the risk of developing depression in a large sample of elderly French participants (aged ≥65 years) followed for 10 years (Dijon portion of the Three-City Study, 1999-2010). Depression was defined as either having major depressive symptoms according to the Mini-International Neuropsychiatric Interview or taking antidepressant medication. The authors fitted marginal structural models to examine the relations of BMI and blood pressure with depression. Among subjects who were depression-free at baseline (n = 3,090), 478 developed incident depression over 10 years of follow-up. The analyses showed that after baseline values and time-dependent confounders were controlled, subjects with high BMI at follow-up had an increased adjusted risk of developing depression compared with subjects with normal BMI (risk ratio = 1.60, 95% confidence interval: 1.03, 2.51). Compared with subjects with normal blood pressure, those with high blood pressure were not at increased risk of incident depression, whereas those with low blood pressure had a higher risk of developing depression. These findings provide some epidemiologic support for implication of lifestyle risk factors in the development of depression in the elderly. Future studies should focus on evaluating lifestyle and obesity interventions among the elderly.