Mortality in Type 1 Diabetes in the DCCT/EDIC Versus the General Population

Abstract

OBJECTIVE Historically, mortality in type 1 diabetes has exceeded that in the general population. We compared mortality in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study cohort to that of the current general U.S. population. RESEARCH DESIGN AND METHODS The DCCT (1983–1993) compared intensive versus conventional therapy, with HbA1c levels of ∼7 vs. 9%, respectively, over an average of 6.5 years of treatment. EDIC is the observational follow-up study of the DCCT (1994 to the present). Vital status was ascertained for 97.5% of the original DCCT cohort (n = 1,441) after a mean of 27 years follow-up. Expected mortality during DCCT/EDIC was estimated using the current age-, sex-, and race-specific risks in the general U.S. population, and the observed versus expected mortality compared using standardized mortality ratios (SMRs) and Poisson regression models. RESULTS Mortality in the DCCT intensive therapy group was nonsignificantly lower than that in the general U.S. population (SMR = 0.88 [95% CI 0.67, 1.16]), whereas mortality in the DCCT conventional therapy group was significantly greater than that in the general population (SMR = 1.31 [95% CI 1.05, 1.65]). The SMR increased with increasing mean HbA1c, and above an HbA1c of 9%, the rate of increase in SMR among females was greater than that among males. CONCLUSIONS Overall mortality in the combined DCCT/EDIC cohort was similar to that of the general population but was higher in the DCCT conventional therapy group. Mortality increased significantly with increasing mean HbA1c, more so among females than males, especially for HbA1c >9%.