Population-Based Study of Impaired Glucose Tolerance and Type II Diabetes in Wadena, Minnesota

Abstract

The Wadena City Health Study was undertaken to assess the nature of type II (non-insulin-dependent) diabetes and its relationship to aging. This article reports the study methodology and prevalence estimates for type II diabetes and impaired glucose tolerance (IGT) for the adult population of Wadena, Minnesota. The sampling frame for the study included all known diabetic individuals and all other residents based on a complete citywide census of residents ≥20yr of age. A stratified random sample that included three stratifying factors (age [20–39, 40–59, ≥60 yr], sex, and self-reported weekly use of any prescribed medication was drawn from the other residents). The study protocol required diet preparation and two full mornings of testing. Data collected included height, weight, and blood pressure measurements and both a personal interview and a medications questionnaire. A 75-g oral glucose tolerance test (OGTT) and a test with a standard liquid meal (Ensure-Plus challenge test [EPCT], Ross) were done on two mornings, with the order of testing randomly assigned. Clinical tests included one-time samples for hemoglobin, glycosylated hemoglobin, plasma cholesterol, triglycerides, and lipoproteins. Blood samples for glucose and creatinine assays were taken during the OGTT; blood samples for glucose, free fatty acid, creatinine, and C-peptide were taken during the EPCT. Urine collections were performed for both challenge tests and assayed for C-peptide and creatinine. Seventy-one percent of the known diabetic subjects, and 65% of the stratified random sample participated in the study. The mean age of the oldest men and women in the stratified random sample was older for the nonparticipants. Otherwise, no systematic differences were observed between study participants and nonparticipants. Both National Diabetes Data Group (NDDG) and World Health Organization (WHO) criteria were used to clarify the current diabetes status of study participants. Age- and sex-standardized (1980 U.S. census) estimates of the prevalence of type II diabetes and glucose intolerance were calculated. Based on NDDG criteria, the prevalance of type II diabetes was 7.8%, and the prevalance of IGT was 5.3%. WHO criteria placed the prevalence of type II diabetes and IGT at 8.1 and 15.0%, respectively. The implications of the high total prevalence of hyperglycemia are discussed.