Glycemic control in diabetic American Indians - Longitudinal data from the Strong Heart Study

OBJECTIVE - To describe glycemic control and identify correlates of elevated HbA(1c) levels in diabetic American Indians participating in the Strong Heart Study which is a longitudinal study of cardiovascular disease in American Indians in Arizona, Oklahoma, South Dakota, and North Dakota. RESEARCH DESIGN AND METHODS - This analysis sis is based on data from the baseline (1989-1992) and first follow-up (1994 similar to 1995) examinations of the Strong Heart Study. The 1,581 diabetic participants included in this analysis were aged 45-74 years at baseline, were diagnosed with diabetes before and at baseline, and had their HbA1(c),levels measured at followup. HbA(1c) was used as the index of glycemic control. Characteristics that may affect glycemic control were evaluated for cross-sectional and longitudinal relationships by analysis of covariance and multiple regression. RESULTS - There was no significant difference between median HbA(1c) at baseline (8.4%) and at follow-up (8.5%). Sex, age (inversely), and insulin and oral hypoglycemic agent therapy were significantly related to HbA(1c), levels in both the cross-sectional and longitudinal analyses. Current smoking, prior use of alcohol, and duration of diabetes were significant only for the cross-sectional data. Baseline HbA(1c) significantly and positively predicted HbA(1c) levels at follow-up. Comparison of HbA(1c) by therapy type shows that insulin therapy produced a significant decrease in HbA(1c) between the baseline and follow-up examinations. CONCLUSIONS - Glycemic control was poor among diabetic American Indians participating in the Strong Heart Study Women, patients taking insulin or oral hypoglycemic agents, and younger individuals had the worst control of all the participants. Baseline HbA(1c), and weight loss predicted worsening of control, whereas insulin therapy predicted improvement in control. Additional therapies and/or approaches are needed to improve glycemic control in this population.