To determine the causes of death in Australians with type 1 diabetes mellitus who died aged 40 years or younger.

Retrospective review of autopsy reports at the Department of Forensic Medicine, Sydney, New South Wales, 1 January 1994 – 31 December 2006.

Causes of mortality in people with type 1 diabetes aged ≤ 40 years.

Of the 26 682 autopsy reports, 1914 were for individuals with diabetes (type 1, 400; type 2, 1514). Cardiovascular disease accounted for 51% of deaths (169/333) in people with type 1 diabetes aged > 40 years, versus 13% among those aged ≤ 40 years (9/67; P = 0.001). Acute complications of diabetes (27%; 18/67), unnatural deaths (28%; 19/67), and sudden unexpected deaths (22%; 15/67) were the predominant causes of death in young individuals with diabetes. Sudden unexpected death was more common in those with type 1 diabetes compared with a sex-matched control population in the same age range (22% v 5%; χ2 P < 0.001). Of the sudden unexpected deaths, 10 people were found dead in an undisturbed bed with no cause of death found at autopsy (“dead-in-bed” syndrome; mean age [SD], 30.2 [9.4] years; males : females = 4 :1).

In deceased young people with type 1 diabetes examined by the Coroner, acute diabetic complications, unnatural causes, and sudden unexpected deaths were the predominant causes of death. The relatively high frequency of sudden unexpected deaths, such as dead-in-bed syndrome, requires further investigation.