Impact of glycaemic control, hypertension and insulin treatment on general and cause-specific mortality: an Italian population-based cohort of type II (non-insulin-dependent) diabetes mellitus

The aims of this study were to assess the impact of diabetes and associated variables (fasting plasma glucose, blood pressure, antidiabetic treatment, body mass index) on general and cause-specific mortality in an Italian population-based cohort with Type II (non-insulin-dependent) diabetes mellitus, comprising mainly elderly patients. The patients (n = 1967) who had Type II diabetes were identified in 1988 with an 80 % estimated completeness of ascertainment. In 1995, a mortality follow-up (98 % completeness) of the cohort was done amounting to a total of 11153 person-years. Observed and expected number of deaths were 577 and 428.7, respectively, giving a standardized mortality ratio (SMR) of 1.35 (95% CI 1.24-1.46). The most common underlying causes of death were malignant neoplasm, ischaemic heart disease and cerebrovascular diseases, which accounted for 18 %, 17.8 % and 17.5 % of deaths, respectively. Cardiovascular disease as a whole (international classification of disease ICD-9 390-459) accounted for 260 of 577 deaths (SMR 1.21, 95 % CI 1.07-1.36). In internal analysis, the most important predictors of general mortality were insulin-treatment (relative risk [RR] 1.72, 95% CI 1.19-2.49) and a fasting plasma glucose greater than 8.89 mmol/l ([RR] 1.29, 95 % CI 1.04-1.60), whereas the most important predictors of cardiovascular diseases were insulin-treatment and hypertension. In conclusion, this population-based study showed: 1) slight mortality excess of 35 % in Type II diabetes being associated with 2) a 30 % increased mortality in subjects with baseline fasting glucose greater than 8.89 mmol/l and 3) a 40 % increased risk of death from cardiovascular diseases in hypertensive patients.