Cardiovascular risk factors prior to the development of non-insulin-dependent diabetes mellitus in persons with impaired glucose tolerance: the Hoorn Study

The aim of the study was to analyze cardiovascular risk factors as predictors for developing noninsulin dependent diabetes mellitus (NIDDM) in people with impaired glucose tolerance. A cross-sectional survey of glucose tolerance was conducted in people, aged 50-74, who were randomly selected from the registry of the middle sized town Hoorn (The Netherlands). Based on the mean values of two oral glucose tolerance tests, people were classified in glucose tolerance categories according to the WHO criteria. The mean follow-up time was 36 months (range 13-55 months). The cumalative incidence of NIDDM was 34% (95% CI 16.9-45.1). In multiple logistic regression analysis, cardiovascular risk factors at baseline did not predict the conversion from impaired glucose tolerance to NIDDM, in contrast with the two-hour plasma glucose level (odds ratio 3.56, p < 0.001) and the fasting proinsulin level, as one of the determinants of beta-cell dysfunction (Odds ratio 2.1, p < 0.05). The baseline HDL-cholesterol level, one of the components of the insulin resistance syndrome, was associated with the conversion from impaired glucose tolerance to normal glucose tolerance (Odds ratio 1.58, p < 0.05). The results of our study seem to support the hypothesis that conversion from impaired glucose tolerance to normal glucose tolerance depends on insulin resistance and the development of NIDDM from impaired glucose tolerance depends on beta-cell dysfunction.