Hematocrit and risk of coronary heart disease: the Puerto Rico Health Program.

Hematocrit was determined in 2555 rural and 6151 urban men age 45 to 64 years participating in the Puerto Rico Health Program, a prospective epidemiologic study of coronary artery disease (CAD). These participants were reexamined three additional times and mortality by cause and coronary heart disease (CHD) morbidity were carefully documented for 8 years of follow-up. Since hematocrit (Hct) is an indirect measure of blood viscosity, its value an an independent risk factor of CHD was evaluated. Within the Puerto Rican cohort, Hct is slightly lower in older age groups, and appears slightly lower in the rural than in the urban area. In the rural area 4.6% had Hct values below 40%; in the urban area 3.0% were below 40%. A higher Hct level was associated with cigarette smoking, higher relative weight, higher blood pressure, and higher serum cholesterol. An elevated Hct level was also associated with an increased risk of myocardial infarction (MI), coronary insufficiency or CHD death in the urban area. Incidence of MI, coronary insufficiency, or CHD death was more than double in the high hematocrit group (Hct greater than 49%) compared to the low group (Hct less than 42%). Using a multivariate logistic function, the relationship remained statistically significant after adjustment for the above mentioned risk factors. These results provide further insight concerning the issue of the potential impact of elevated Hct as an independent risk factor contributing to the incidence of CHD mortality and morbidity.