Depression Increases Mortality in Patients with Type 2

Both major and minor depression were found to be associated with significantly higher mortality in patients with type 2 diabetes compared with nondepressed patients with diabetes alone.

The study assessed whether patients with comorbid minor and major depression and type 2 diabetes had a higher mortality rate over a 3-year period compared with patients with diabetes alone.

In a large health maintenance organization (HMO), 4,154 patients with type 2 diabetes were surveyed and followed for up to 3 years. Patients initially filled out a written questionnaire, and HMO-automated diagnostic, laboratory, and pharmacy data and Washington State mortality data were collected to assess diabetes complications and deaths. Cox proportional hazards regression models were used to calculate adjusted hazard ratios of death for each group compared with the reference group.

There were 275 (8.3%) deaths in 3,303 patients without depression compared with 48 (13.6%) deaths in 354 patients with minor depression and 59 (11.9%) deaths among 497 patients with major depression. A proportional hazards model with adjustment for age, sex, race/ethnicity, and educational attainment found that compared with the nondepressed group, minor depression was associated with a 1.67-fold increase in mortality (P = 0.003), and major depression was associated with a 2.30-fold increase (P < 0.0001). In a second model that controlled for multiple potential mediators, both minor and major depression remained significant predictors of mortality.

Both major and minor depression were found to be associated with significantly higher mortality in patients with type 2 diabetes compared with nondepressed patients with diabetes alone. These data are similar to findings from several large epidemiologic studies that showed that patients with comorbid depression and diabetes compared with those with diabetes alone had a significantly higher mortality risk.

Depression may be associated with increased mortality in patients with diabetes because of both behavioral and biologic factors. Depression has been shown to be associated with poor adherence to self-care regimens in patients with diabetes (diet, exercise, and cessation of smoking),[4,5] poor adherence to all three categories of disease control medications (i.e., oral hypoglycemic, lipid-lowering, and antihypertensive),[4] and a twofold higher likelihood of having three or more of eight cardiac risk factors.[6] Depression may also be associated with mortality due to poor glucose regulation[7,27] based on hypothalamic-pituitary axis abnormalities[9,27] as well as increased risk of myocardial infarction[12-14] and stroke[12-14] due to the association of depression with increased platelet adhesiveness and aggregation, increased markers of inflammatory response such as C-reactive protein levels, endothelial dysfunction, increased sympathoadrenal activity, and higher QT variability.[9,10]

In conclusion, in a population-based sample of patients with type 2 diabetes, both major depression and minor depression were associated with increased mortality rates over a 3-year period.

Diabetes Care. 2005 Nov;28(11):2668-72.

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