Type 2 Diabetes and Prediabetes Incidence in Western Alaska Native People: The Western Alaska Tribal Collaborative for Health (WATCH) Study
METHODS: The WATCH cohort is comprised of data from three prospective cohort studies. Baseline demographic and clinical data were consolidated. Identical methods were used to collect prospective data beyond baseline exam. DM2 and prediabetes were defined using American Diabetes Association 2010 criteria. Incidence was age-and sex-adjusted to the US 2010 Census by direct methods.
RESULTS: Prospective follow-up participants represent 69% (n=2,754) of the WATCH baseline cohort (n = 3,985). Mean age was 41.4 years (SD 16) and 56% were female; 30% had prediabetes; 38% had BMI ≥30 kg/m2; 68% were current or past smokers, but only 6.5% had a family history of diabetes. DM2 was diagnosed prior to baseline in 76 (2.8%) participants and an additional 48 (1.7%) were detected at baseline exam. Excluding baseline DM2, 53 incident cases of DM2 were identified in 2,630 participants over an average follow-up of 6.2 years. Adjusted DM2 incidence was 4.3/1,000 person-years (PY; 95% CI 2.9, 5.0). Excluding baseline prediabetes, 387 incident cases of prediabetes were identified in 1,841 remaining participants; adjusted prediabetes incidence was 44.5/1,000 PY (95% CI 39.5, 49.5). DM2 incidence is less than half that of the U.S. general population (est. 9.3/1,000 PY), but prediabetes incidence is higher; prediabetes prevalence is similar to U.S. populations with higher diabetes rates (2011 CDC National Diabetes Fact Sheet).
CONCLUSIONS: Despite low DM2 incidence, prevalence and incidence of prediabetes is much higher in western AN people. Ongoing analyses of risk and lifestyle factors may provide information about protective factors, such as traditional diet and physical activity patterns in this unique population.