OBJECTIVE -The rising prevalence of obesity and high prevalence of diabetes among Pima Indians suggest that the incidence of diabetes has risen over time. We examined trends in the incidence rate of type 2 diabetes among Pima Indians between 1965 and 2003.RESEARCH DESIGN AND METHODS -Incidence rates were computed independently in three 13-year time periods in Pima Indians aged Ն5 years. Diabetes was defined by the presence of at least one of two criteria: 1) 2-h plasma glucose concentration Ն200 mg/dl (11.1 mmol/l) or 2) hypoglycemic treatment.RESULTS -Among 8,236 subjects without diabetes at baseline, 1,005 incident cases occurred during follow-up. Age-and sex-adjusted incidence rates of diabetes were 25.3 cases/ 1,000 patient-years (95% CI 22. 5-28.0) in 1965-1977, 22.9 cases/1,000 patient years (20.0 -25.8) in 1978 -1990, and 23.5 cases/1,000 patient years (20.5-26.5) in 1991-2003 (P ϭ 0.3). The incidence rate in subjects aged 5-14 years was 5.7 (1.9 -17.4) times as high in the last as in the first period, but the rate declined in those aged 25-34 years (incidence rate ratio 0.6 [0.4 -0.8]). Sex-adjusted prevalence increased significantly over time only in those aged 5-24 years (P trend Ͻ 0.0001).CONCLUSIONS -The overall incidence of diabetes among Pima Indians remained stable over the past four decades, with a significant rise occurring only in the youth.
Diabetes Care 30:1758-1763, 2007D iabetes prevalence is increasing worldwide, especially in populations transitioning from traditional to modern lifestyles (1,2). While prevalence and incidence of type 2 diabetes are highest among adults, youth are increasingly affected (3,4). Whether the rising prevalence of type 2 diabetes is due to increasing incidence, declining mortality, or both is unclear (5-7). Projections based on increasing life expectancy, population growth, and progressive urbanization predict substantial increases in the prevalence of diabetes for decades to come (5). These estimates may be too low, however, since they do not account for the increasing frequency and magnitude of obesity and other major risk factors for diabetes.We examined secular trends in the incidence rate of type 2 diabetes over the past 40 years in Pima Indians, a population with a very high prevalence and incidence of diabetes (8). Previous observations (9,10) suggest that diabetes was either rare or largely unrecognized among Pimas around the 1900s. At that time, increasing settlement of the area by people of European derivation led to diversion of the Pimas' water supply and disruption of their agriculture (10). The loss of water resulted in curtailment of subsistence farming and led to fundamental changes in their way of life (11). In the late 1930s, a review of medical records from the hospitals serving the population identified 21 Pima Indians with diabetes. The author concluded that the prevalence of diabetes was similar to that in the U.S. population (12). By the 1950s, many more Pimas were known to have diabetes, (13) and since then, a rising prevalence of obesity...