Epidemiology of type 2 diabetes: risk factors.

A number of cross-sectional and prospective studies that compared the insulin sensitivity of various national and ethnic populations within the U.S. to the total U.S. population were analyzed to find possible risk factors for the development of type 2 diabetes. It was found that the risks for diabetes in African-Americans, Hispanics, and Native Americans are approximately 2, 2.5, and 5 times greater, respectively, than in Caucasians. Studies of the prevalence of type 2 diabetes in Mexican Americans and non-Hispanic whites in San Antonio showed that there is an inverse relationship between socioeconomic status and the prevalence of diabetes. It also appears that cultural effects lead to an increased incidence of obesity in these populations, which may lead to insulin resistance. Genetic factors may also be a contributing factor. A 5-year, prospective study of insulin resistance in Pima Indians showed a relationship between impaired glucose tolerance and subsequent development of type 2 diabetes. In a 7-year study in Mexican Americans, those subjects who had both high insulin secretion and impaired insulin sensitivity had a 14-fold increased risk of developing type 2 diabetes. Regardless of cultural and ethnic factors, the San Antonio Heart Study, which compared Mexican Americans and non-Hispanic whites, showed that in both groups, the strongest predictors of developing type 2 diabetes are elevated fasting insulin concentrations and low insulin secretion.