Depression but not non-persistence to antidiabetic drugs is associated with mortality in type 2 diabetes: A nested case-control study

Aims: To measure the effect of depression on mortality of individuals newly treated with antidiabetic drugs, accounting for non-persistence to treatment. Methods: We conducted a nested case-control study within a cohort of newly treated individuals with diabetes. Using Quebec administrative data, we identified all-cause, diabetes-related, cardiovascular-related and major cardiovascular event deaths during a maximum follow-up of eight years. Each case was matched with up to 10 controls by age, sex, follow-up, and comorbidity index. We used conditional logistic regressions to estimate the effect of depression on mortality, adjusting for non-persistence to antidiabetic drug treatment, and other variables. Results: We retrieved 13,558 deaths, of which 3,652 were related to cardiovascular diseases, 2,112 to major cardiovascular events, and 311 to diabetes. Depression was associated with an increased risk of all-cause and cardiovascular-related deaths, with adjusted odds ratios (ORs) ranging from 1.32 (95% CI: 1.21–1.45) to 1.72 (95% CI: 1.57–1.88) depending on the model, but not with diabetes-related mortality. Conclusion: Depression is independently associated with all-cause and cardiovascular-related mortality in individuals with type 2 diabetes, even when adjusting for non-persistence to antidiabetic drug treatment. Identifying risk factors for depression and implementing a screening and proper treatment for depression may help reducing mortality.