Metabolic syndrome and incident depressive symptoms in young and middle-aged adults: A cohort study

Background:: Recent studies on the prospective association between metabolic syndrome (MetS) and depression have reported conflicting findings. Methods:: A cohort study was performed with 115,223 middle-aged adults, free of depression at baseline, who underwent at least 2 comprehensive exams between 2012 and 2015. MetS was assessed according to the National Cholesterol Education Program Adult Treatment Panel III. The study endpoint was new onset of depression, defined as a Center for Epidemiologic Studies-Depression Scale score ≥ 16. Results:: Over 253,451.6 person-years, 6,833 participants developed depression. When the participants with 0 MetS components were set as a reference, the multivariable-adjusted hazard ratio (HR, 95% confidence interval [CI]) for incident depression formed a U-shaped curve with the number of MetS components (p for trend = 0.229): 1 (1.07 [1.02–1.15]); 2 (0.92 [0.82–1.06]); 3 (0.85 [0.78–1.07]); 4 (1.16 [1.06–1.32]); and 5 MetS components (1.25 [1.10–1.54]). The presence or absence of MetS was not significant in new-onset depression. In examining potential clustering and synergistic effects of the constituent parts, waist circumference was the major driving factor of incident depression, and its relative excess risk due to interaction increased with the number of combinations. Limitations:: We used a self-reported depression scale, and the follow-up period was relatively short. Conclusions:: Future studies investigating the risk for incident depression should place more focus on the number of MetS abnormalities and specific MetS factors, such as waist circumference, than the presence or absence of MetS.