HEMATOCRIT LEVELS AND PHYSIOLOGICAL FACTORS IN RELATIONSHIP TO CARDIOVASCULAR RISK IN TECUMSEH, MICHIGAN

Objective: To investigate the relationship between hematocrit, blood p ressure and other known cardiovascular risk factors. Design: The Tecum seh Blood Pressure Study includes a cohort of subjects of average age 29.5 years (346 male, 277 female) who reside in Tecumseh, Michigan, US A. Methods: The body weight; home, work and clinic blood pressures; he matocrit level, plasma renin activity, baseline and mentally stimulate d plasma catecholamines level; and fasting glucose, insulin and lipids levels were obtained. Since menstruation and childbearing affect the hematocrit, results are presented only for males. The males in Tecumse h were divided into tertiles of hematocrit (group I less than or equal to 43.25, group II 43.26-45.2 and group III >45.2%). Results: Higher hematocrit levels were significantly related to higher blood pressures at home, at work and in the clinic, although all of the values measur ed were within the normotensive range (128/79 mmHg clinic blood pressu re in group III). The metabolic factors weight, cholesterol, triglycer ides, insulin and glucose levels were significantly elevated in group III. The weight affected only the relationship of hematocrit to plasma insulin levels and not the other variables including the blood pressu re. Groups II and III showed signs of sympathetic overactivity; their plasma renin levels, heart rates and norepinephrine levels after menta l stimulation were elevated. Conclusions: Although the relationship of blood pressure to the hematocrit level was previously known, in Tecum seh hematocrit is also found to be associated with several other cardi ovascular risk factors and with signs of a hypersympathetic state. We intend to evaluate prospectively the relative prognostic significance of a higher hematocrit level versus the other associated risk factors.