Mortality in childhood-onset type 1 diabetes mellitus with onset between 1959 and 1996: A population-based study in Hokkaido, Japan.

Aim: To examine the mortality rate and causes of death in childhood-onset type 1 diabetes in Japan. Methods: For a median 36.7 years, we followed 391 patients under the age of 15 years who developed type 1 diabetes between 1959 and 1996. We calculated the mortality rate per 100,000 person-years and the standardised mortality ratio (SMR) according to risk factors. Results: The mortality rates and SMRs were 823 and 8.8 with onset during 1959-1979, 370 and 5.9 with onset during 1980-1989, and 133 and 3.2 with onset during 1990-1996, respectively. The mortality rates and SMRs were 359 and 8.4 in men, and 235 and 6.0 in women. Mortality rates and SMRs were 452 and 7.3 in patients with diabetes onset before puberty and 514 and 6.3 in patients with onset after puberty. The main causes of death with shorter disease duration were sudden death, accident/suicide, and acute diabetic complications. With a more than 30-year disease duration, the main causes of death were end-stage renal disease and cardiovascular disease. Conclusions: This cohort study revealed a decrease in the mortality rate between 1959-1979 and 1990-1996 in patients with childhood-onset type 1 diabetes in Japan. Patients with onset after puberty had a higher mortality rate than those with onset before puberty.