Depression and metabolic syndrome in the older population: A review of evidence

Background: Metabolic syndrome (MetS) has been shown to be associated with depression in older adults but the results are mixed. We summarized and evaluated the association between depression and MetS in people aged 60 years or over. Methods: Relevant published studies from January 1997 to July 2017 were identified by searching two electronic databases: PubMed/Medline and EMBASE. Observational studies were considered. Results: Twelve studies were included in the systematic review. Depression seemed to be related with MetS in the majority of the studies (10/12 = 83.3%). As far as the longitudinal studies are concerned, the onset of depression was related to MetS in 2 out of 3 studies (66.6%), while a relation between chronicity of depression and MetS was reported (1 study). Regarding cross-sectional studies, 7 out of 9 (77.7%) concluded that there was a positive association between depression and MetS. Mixed evidence was found among studies concerning the association between depression and the individual components of MetS. Four out of ten studies (40%) reported that depression was significantly associated with the waist circumference, a component of MetS. Limitations: There was a high degree of heterogeneity between studies regarding their design. Only studies written in English, from peer-reviewed journals were included. Conclusions: Depression seemed to be significantly associated with MetS in people aged 60 years or over. Among the components of MetS, abdominal obesity seemed to be associated more strongly and consistently with depression. The direction of the causality and mechanisms underlying the relationship are still largely unknown.