Hematocrit and the Incidence of Type 2 Diabetes in the Pima Indians
- Marshall K. Tulloch-Reid, MBBS, DSC,
- Robert L. Hanson, MD, MPH,
- Aramesh Saremi, MD,
- Helen C. Looker, MBBS,
- Desmond E. Williams, MBCHB, PHD,
- Jonathan Krakoff, MD and
- William C. Knowler, MD, DRPH
- From the Diabetes and Arthritis Epidemiology Section, Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona
- Address correspondence to William Knowler, MD, DrPH, Chief, Diabetes and Arthritis Epidemiology Section, National Institutes of Health, 1550 East Indian School Rd., Phoenix, AZ 85014. E-mail: knowler{at}nih.gov
Several prospective studies have shown that a high hematocrit (or hemoglobin) predicts type 2 diabetes (1–6). However, the reasons for this association have not been fully explored.
Hematocrit has been positively correlated with hyperinsulinemia and conditions associated with insulin resistance such as high blood pressure, elevated serum triglycerides, low HDL cholesterol, and central obesity and could therefore be associated with insulin resistance (7,8). On the other hand, hematocrit is also a major determinant of blood viscosity (9). An elevated blood viscosity is thought to contribute to the development of insulin resistance by reducing blood flow to skeletal muscle, thereby interfering with insulin-mediated glucose uptake in this tissue (10).
The aim of this study was to examine the association between hematocrit and type 2 diabetes incidence in the Pima Indians and to determine whether any association between hematocrit and diabetes incidence was altered by adjustment for fasting insulin.
RESEARCH DESIGN AND METHODS
The population studied was part of an ongoing epidemiological study of diabetes that has been conducted in the Gila River Indian community since 1965 (11). Subjects selected for analysis were ≥20 years old; had height, weight, and hematocrit measurements; …
