Cause-specific mortality in type 2 diabetes. The Verona Diabetes Study

Abstract

Objective: This population-based study, carried out in the framework of the Verona Diabetes Study, investigated mortality from specific causes in known type 2 diabetic patients.

Research design and methods: A cohort of 7,148 known type 2 diabetic patients (3,366 men and 3,782 women) was identified on 31 December 1986 and followed up for 5 years (1987-1991). Underlying causes of death were obtained from death certificates and were coded according to the International Classification of Diseases, Ninth Revision. Cause-specific death rates of diabetic subjects were compared with those of the inhabitants of Verona. By 31 December 1991, 1,550 diabetic subjects (744 men and 806 women) had died.

Results: The standardized mortality ratio (SMR) for all causes of death was 1.42 (95% CI 1.35-1.50). The highest SMRs were for the following specific causes: diabetes (SMR 4.47 [3.91-5.10]), gastrointestinal diseases (1.83 [1.50-2.21])--particularly liver cirrhosis (2.52 [1.96-3.20])--and cardiovascular diseases (1.34 [1.23-1.44]), particularly cerebrovascular (1.48 [1.25-1.73]) and ischemic heart diseases (1.41 [1.24-1.62]). A significantly higher than expected risk of mortality for cardiovascular causes was already present in the first 5 years after diagnosis and decreased with age. Type 2 diabetic patients treated with insulin had a higher risk of dying than those treated orally or by diet.

Conclusions: The highest SMRs in the diabetic cohort were for diabetes and liver cirrhosis. The mortality risk for cardiovascular diseases, although significantly higher than expected, was much lower in Italian type 2 diabetic patients than that reported for American patients. The evidence of an early effect on mortality suggests that prevention, early diagnosis, and treatment should be improved.