Association between all-cause mortality and severity of depressive symptoms in patients with type 2 diabetes: Analysis from the Japan Diabetes Complications Study (JDCS)

Objective The aims of this study are to confirm whether the excess mortality caused by depressive symptoms is independent of severe hypoglycemia in patients with type 2 diabetes mellitus (T2DM) and to evaluate the association between all-cause mortality and degrees of severity of depressive symptoms in Japanese patients with T2DM. Methods A total of 1160 Japanese patients with T2DM were eligible for this analysis. Participants were followed prospectively for 3 years and their depressive states were evaluated at baseline by the Center for Epidemiologic Studies Depression Scale (CES-D). Cox proportional hazards model was used to evaluate the relative risk of all-cause mortality and was adjusted by possible confounding factors, including severe hypoglycemia, all of which are known as risk factors for both depression and mortality. Results After adjustment for severe hypoglycemia, each 5-point increase in the CES-D score was significantly associated with excess all-cause mortality (hazard ratio 1.69 [95% CI 1.26–2.17]). The spline curve of HRs for mortality according to total CES-D scores showed that mortality risk was slightly increased at lower scores but was sharply elevated at higher scores. Conclusion A high score on the CES-D at baseline was significantly associated with all-cause mortality in patients with T2DM after adjusting for confounders including severe hypoglycemia. However, only a small effect on mortality risk was found at relatively lower levels of depressive symptoms in this population. Further research is needed to confirm this relationship between the severity of depressive symptoms and mortality in patients with T2DM.