Depressive Symptoms Predict Increased Mortality Rates in Both Men and Women with Type 1 Diabetes

Depression is more prevalent in patients with type 1 diabetes than in the general population, with some studies suggesting that patients with comorbid type 1 diabetes and depression are at higher mortality risk.

During a session Tuesday at the American Diabetes Association’s 74th Scientific Sessions, Catherine E. Fickley, MPH, CPH, of the Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh in Pennsylvania, reported on possible links between depression and mortality in patients with type 1 diabetes.

Fickley referenced a recent meta-analysis of clinical trials suggesting that 12.0% of participants with type 1 diabetes had clinical depression compared with just 3.2% of healthy controls.

Both type 1 diabetes and depression have each been associated with an increased mortality risk, but whether depressive symptoms increase mortality risk in type 1 diabetes is unclear.

“Those with type 1 diabetes and depression are at increased risk of several diabetes-related complications. A relationship between depression and increased mortality in the general population, as well as in those with type 2 diabetes, has been previously reported. To the best of our knowledge, there has only been one other study to examine the relationship between depression and mortality in patients with type 1 diabetes,” Fickley said.

Fickley and colleagues studied depressive symptoms and subsequent mortality in the prospective Pittsburgh Epidemiology of Diabetes Complications (EDC) study of childhood onset type 1 diabetes, comprising 223 men and 235 women with a mean baseline age of 28.7 years and mean diabetes duration of 19.9 years.

Study participants self-administered a questionnaire known as the Beck Depression Inventory (BDI) at baseline and biennially thereafter during 20 years of follow-up. Researchers used multivariable Cox models and time-varying analyses to assess independent associations between depressive symptoms and mortality. They also calculated hazard ratios (HR).

During 20 years of follow-up, 94 deaths (51 men, 43 women) occurred, representing slightly more than 20% of the study population. BDI score was univariately associated with mortality (HR=1.05, 1.03 to 1.07, p<.0001). This association persisted in multivariate analyses allowing for duration of disease, education, calories consumed, hypertension, blood pressure medication, HDL, total cholesterol, white blood cell count, HbA1c level, waist-to-hip ratio, type A behavior, and coronary artery disease (HR=1.04, 1.02 to 1.07, p<.0001).

The presence of a gender difference in mortality associated with depression in type 1 diabetes patients was assessed in the EDC study, but no interaction was observed (p=0.93), in contrast to previous findings. Fickley said that investigators in the other study of depression and mortality in type 1 diabetes employed antidepressant use as their measure of depression, resulting in an association of depression with an increased risk of mortality in women but not in men. Fickley maintained relying only on antidepressant purchases was a limitation, as it did not capture patients with undiagnosed or untreated depression.

Regarding the self-reporting aspect of the BDI questionnaire, Fickley said, “A strength of this study is the use of the BDI in assessing depressive symptoms to capture both those using antidepressants and those who are not but who still have symptoms. Studying the effects of self-reported depressive symptoms in those with type 1 diabetes helps to fill a significant gap in the literature.”

In summarizing the findings of the study, Fickley said, “Based on these results, in this cohort of people with type 1 diabetes, those who had more depressive symptoms measured at baseline and over time appear to be at an increased risk of mortality, even after allowing for likely mediators. In addition, antidepressant use was not a major confounder.”

“We conclude that in this type 1 diabetes cohort, depressive symptoms are an independent predictor of mortality in both men and women. In addition, while coronary artery disease may partially account for this association, it is not its sole mediator. As depressive symptoms seem to predict mortality in type 1 diabetes, further work should address the value of screening for, and treatment of, depressive symptoms in this population,” Fickley said.