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

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.