Objective: Little is known concerning the primary cause(s) of mortality in type 1 diabetes responsible for the excess mortality seen in this population.

Research Design and Methods: The Allegheny County (Pennsylvania) childhood-onset (age<18 yrs) type 1 diabetes registry (n=1,075) with diagnosis from 1965-79 was used to explore patterns in cause-specific mortality. Cause of death was determined by a mortality classification committee of at least 3 physician epidemiologists, based on the death certificate and additional records surrounding the death.

Results: Vital status for 1,043 (97%) participants was ascertained as of 1 January 2008, revealing 279 (26.0%) deaths overall (141 females and 138 males). Within the first 10 years after diagnosis, the leading cause of death was acute diabetes complications (73.6%), while during the next 10 years, deaths were nearly evenly attributed to acute (15%), cardiovascular (22%), renal (20%), or infectious (18%) causes. After 20 years duration, chronic diabetes complications (cardiovascular, renal, or infectious) accounted for >70% of all deaths, with cardiovascular disease as the leading cause of death (40%). Women (p<0.05) and African-Americans (p<0.001) have significantly higher diabetes-related mortality rates than men and Caucasians, respectively. SMRs for non-diabetes-related causes do not significantly differ from the general population (violent deaths: SMR=1.2, 0.6-1.8; cancer: SMR=1.2, 0.5-2.0).

Conclusions: The excess mortality seen in type 1 diabetes is almost entirely related to diabetes and its comorbidities, but varies by duration of diabetes and particularly affects women and African-Americans.