INS and diabetes mellitus: The target populations and methods used in other US-based studies make comparisons to this study problematic.23,24,25 For comparison with the benchmark Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR),23,24 we conducted an additional analysis of DR incidence by age of diabetes diagnosis (before or after 30 years) plus whether the American Indian and Alaska Native patients were taking insulin.