Relationship between diabetes and mortality: a population study using record linkage

Abstract

Objective: To determine patterns and causes of mortality for patients with diabetes in a district health authority

Research design and methods: The study used cross-sectional record linkage, combining an electronic death register with a diabetic patient register constructed from a variety of routine health data sources collected from 1991 to 1997. The study was conducted in Cardiff and the Vale of Glamorgan, Wales, U.K., and included all diabetic deaths between 1993 and 1996.

Results: Of 1,694 deaths in patients with known diabetes, only 674 (39.8%) had diabetes recorded as an immediate or antecedent cause of death. Mortality rates were 41.8 per 1,000 for the diabetic population and 10.1 per 1,000 for the nondiabetic population. The standard mean ratio for the diabetic population was 1.24 (95% CI 1.12-1.35), with the risk of mortality relative to the nondiabetic population decreasing with age. Males with diabetes lost an average of 7.0 years from the year of diagnosis, and females with diabetes lost an average of 7.5 years. The most common cause of death was cardiovascular disease, which accounted for 49.1% of deaths in the diabetic population.

Conclusions: Diabetes is recorded as a cause of death on a minority of death certificates for patients with diabetes. Using death certificates in isolation, therefore, is a poor method of estimating diabetic mortality, but results can be improved with the use of record linkage techniques. Patients with diabetes have an excess risk of mortality compared with the nondiabetic population. Life-years lost for patients with diabetes is strongly related to age at diagnosis and is a means of expressing mortality without relying on accurate prevalence data.