Depression Increases Mortality for Diabetes Patients

Recent evidence suggests that depression is linked to increased mortality among patients with diabetes. This study examined the association of depression with all-cause and cause-specific mortality in diabetes.

They conducted a prospective cohort study of primary care patients with Type 2 diabetes at Group Health Cooperative in Washington state. They used the Patient Health Questionnaire (PHQ-9) to assess depression at baseline and reviewed medical records supplemented by the Washington state mortality registry to ascertain the causes of death.

The results showed that, among a cohort of 4,184 patients, 581 patients died during the follow-up period. Deaths occurred among 428 (12.9%) patients with no depression, among 88 (17.8%) patients with major depression, and among 65 (18.2%) patients with minor depression. Causes of death were grouped as cardiovascular disease, 42.7%; cancer, 26.9%; and deaths that were not due to cardiovascular disease or cancer, 30.5%. Infections, dementia, renal failure, and chronic obstructive pulmonary disease were the most frequent causes in the latter group. Adjusting for demographic characteristics, baseline major depression (relative to no depression) was significantly associated with all-cause mortality (hazard ratio [HR]=2.26, 95% confidence interval [CI], 1.79-2.85), with cardiovascular mortality (HR = 2.00; 95% CI, 1.37-2.94), and with non-cardiovascular, non-cancer mortality (HR = 3.35; 95% CI, 2.30-4.89). After additional adjustment for baseline clinical characteristics and health habits, major depression was significantly associated only with all-cause mortality (HR = 1.52; 95% CI, 1.19-1.95) and with death not caused by cancer or atherosclerotic cardiovascular disease (HR = 2.15; 95% CI, 1.43-3.24). Minor depression showed similar but non-significant associations.

From the results it was concluded that, patients with diabetes and coexisting depression face substantially elevated mortality risks beyond cardiovascular deaths. This study is the first to examine cause-specific mortality and depression in a diabetes cohort. Emerging epidemiologic results among worldwide populations not limited to patients with diabetes have reported positive links between depression and mortality across a wide spectrum of non-cardiovascular causes, including cancer, human immunodeficiency virus, chronic obstructive pulmonary disease, and rheumatoid arthritis. A large population-based study in Norway confirmed that depression was a risk factor for all major disease-related deaths, not just cardiovascular disease.