Background: Few European studies have used an oral glucose tolerance test (OGTT) to examine the incidence of type 2 diabetes. We determined the incidence of impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and type 2 diabetes in a population from southern Spain.
Material and methods: A population-based cohort study was undertaken in Pizarra, Spain. Baseline data were recorded on age, sex, weight, height, waist and hip circumferences, and diabetes status for 1051 persons, of whom 910 were free of type 2 diabetes (at-risk sample). Of these, 714 completed the 6-year follow-up study. Body mass index, waist-to-hip ratio and weight increase since baseline were calculated. The homeostasis model assessment equations were used to estimate the indices of insulin resistance and beta-cell function. Each person received an OGTT at baseline and after 6 years.
Results: Type 2 diabetes developed in 81 people for a total of 4253 person-years, representing an incidence of 19.1 cases per 1000 person-years (95% confidence interval, 15.3-23.6). Age and the presence of obesity, central obesity and carbohydrate metabolism disorders [IFG (cut off = 100 mg dL(-1), capillary blood glucose level), IGT or both] at baseline were significant markers for the onset of type 2 diabetes during follow-up. After adjusting for these variables, multivariate analysis showed weight increase, waist-to-hip ratio and the indices of insulin resistance and beta-cell function were significantly associated with the risk for type 2 diabetes.
Conclusions: The incidence of type 2 diabetes in a population from southern Spain is high. It is probably associated with the high prevalence of obesity and weight increase in this population.