Depression associated with death in older patients with type 2 diabetes

A study that screened patients with type 2 diabetes in Spain for depression found that depression was associated with higher all-cause mortality in patients older than age 65 years, but not in younger patients.

Older adults with type 2 diabetes and depression had higher mortality risk than those without depression in a recent study.

The DIAbetes and DEpression in Madrid (DIADEMA) study looked at the association between depression and death in outpatients with type 2 diabetes living in Madrid. The study recruited 3,443 patients in 2007 and 727 patients in 2010. Participants had a diagnosis of type 2 diabetes, were ages 30 years and older, and had visited a primary health care center at least twice in the previous year. A total of 3,944 participants were alive in January 2011 and were included in the study population. Cases of depression were identified by a single trained psychologist (75% of patients) or general practitioner (25% of patients) using the MINI 5.0.0 questionnaire or clinical judgment (i.e., the presence of symptoms compatible with depression) and/or the use of antidepressant therapy for at least two months. The main outcome was all-cause mortality. Results were published online on May 13 by Diabetes Research and Clinical Practice.

Overall, 21 patients died in 2011 before being reached for interview by the psychologist or general practitioners. A depression diagnosis was established in 867 (22%) participants, 691 (23.4%) of the 2,955 patients who were interviewed by the psychologist and 176 (18.2%) of the 968 interviewed by general practitioners. During a median 8.1 years of follow-up, 1,104 (28%) patients died. There were significant differences in the mortality rates between patients with and without depression (31.9% vs. 26.9%, respectively; P=0.003). In analyses of factors associated with incidence of all-cause mortality, depression showed an adjusted hazard ratio (HR) of 1.40 (95% CI, 1.20 to 1.65; P<0.001), which was slightly higher in men than women, although the confidence intervals overlapped (HRs, 1.44 [95% CI, 1.13 to 1.84] vs. 1.33 [95% CI, 1.07 to 1.66]). Mortality in patients ages 75 years and older with depression was 9.6% higher (mortality rate ratio, 1.096) than in those without depression (925 vs. 843.9 per 10,000 patient-years, respectively), and the difference was even higher (20.5%) in patients between ages 65 and 75 years (306.6 vs. 254.4 per 10,000 patient-years, respectively). In contrast, among patients younger than age 65 years, mortality was 23.6% lower in those with depression (81.6 vs. 106.8 per 10,000 patient-years, respectively).

Limitations include possible misclassification bias from inaccurate diagnosis of depression and the fact that the study did not evaluate the fluctuations and duration of depression, the authors noted. “More research efforts should be made to understand and minimize the influence of clinical depression on mortality in people with diabetes,” they wrote.