The association between depressive symptoms and systemic inflammation in people with type 2 diabetes: findings from the South London Diabetes Study.

Abstract

The prevalence of depression and depressive symptoms is increased twofold in people with type 2 diabetes compared with the general population and is associated with worse biomedical outcomes and increased mortality. Type 2 diabetes, cardiovascular disease, and depression in nondiabetes subjects are independently associated with raised concentrations of circulating inflammatory markers, but it is not known if a similar association is observed in type 2 diabetes. We tested the hypothesis that higher depressive symptom scores in newly diagnosed type 2 diabetes patients were associated with higher concentrations of inflammatory markers. Depressive symptoms in adults with newly diagnosed type 2 diabetes recruited from primary care were assessed using the Patient Health Questionnaire-9. Twelve markers of inflammation (C-reactive protein [hs-CRP], interleukin-4 [IL-4], IL-6, IL-10, vascular endothelial growth factor [VEGF], tumor necrosis factor-α [TNF-α], IL-1β, IL-1 receptor antagonist [IL-1RA], monocyte chemotactic protein-1 [MCP-1], white blood cell count [WBC], adiponectin, and triglyceride [TG]) were measured. Covariates included sociodemographic factors, adiposity, macrovascular disease, HbA1c, and prescribed medication. The association between each inflammatory marker and depressive symptom score was estimated by multiple linear regression. The baseline cohort consisted of 1,790 participants. After adjusting for covariates, CRP (B = 0.13, P < 0.001), IL-1β (B = 0.06, P = 0.047), IL-1RA (B = 0.13, P < 0.001), MCP-1 (B = 0.11, P = 0.001), WBC (B = 0.13, P < 0.001), and TG (B = 0.10, P < 0.001) were associated with depressive symptoms. Increased inflammation may be involved in the pathogenesis of depressive symptoms in type 2 diabetes and contribute to the increased risk of complications and mortality in this group.