Association Between Obesity, Depression, and Inflammation Among Seventh-day Adventists in the Biopsychosocial Religion and Health Study

The effects of obesity and depression on morbidity and mortality may be mediated by inflammatory processes. Homeostasis within the immune system depends on a balance of pro-inflammatory and anti-inflammatory cytokine molecules, so chronic inflammatory diseases may result from cytokine dysregulation. The target population consisted of 508 Seventh Day Adventists (SDAs) who participated in the Biopsychosocial Religion and Health Study (BHRS), a sub-study of the Adventist Health Study-2. The study was a cross-sectional analysis of the association between obesity, depression, and inflammation after controlling for demographic, socioeconomic, health behavioral, and health status variables among BHRS participants. Obesity was assessed by body mass index (BMI) and waist circumference (WC) measurements, while the Center for Epidemiological Studies Depression Scale 11-item short form was used to measure depression. Enzyme linked immunosorbant assays were utilized to measure the serum concentrations of c-reactive protein (CRP), interleukin-6 (IL-6), interleukin-10 (IL-10) and tumor necrosis factor-a (TNF-a). Statistical analysis was accomplished by multiple linear regression using SPSS version 17. Obesity measurements and depression scores served as predictor variables, while inflammatory marker concentrations functioned as dependent variables in linear regression equations. Control variables included age, gender, ethnicity (Blacks and Whites), education, degree of difficulty meeting family expenses, exercise frequency, diet (vegetarian or nonvegetarian), and inflammatory conditions. Results showed that CRP was positively associated with age, female gender, BMI, WC, and non-vegetarian diet. IL-6 was positively associated with age, BMI, WC, and Black ethnicity, while IL-10 was positively associated with exercise frequency after controlling for all other covariates. In addition, depression scores were positively associated with female gender, BMI, WC, increased difficulty meeting family expenses in the last year, and the diagnosis of an inflammatory condition after controlling for all other factors. However, depression scores were not associated with any of the inflammatory markers based on the regression analysis. In conclusion, the risk for inflammation varied according to age, gender, ethnicity, and overall body mass among SDAs. Lifestyle factors such as exercise and vegetarian diet were associated with reduced inflammation. Therefore, health behavior variables may serve as important components of therapeutic lifestyle interventions and should be studied among distinct sociodemographic populations