Plasma insulin levels and incidence of hypertension in African Americans and whites

Background: Hyperinsulinemia may play an important role in the pathogenesis of hypertension in whites but the role of hyperinsulinemia in hypertension in African Americans is controversial. Subjects and Methods: We studied the relationship between insulin levels an d subsequent incidence of hypertension in 140 African Americans and 237 whi tes who were initially screened for possible participation in the Trials of Hypertension Prevention, phase 1. Plasma insulin and serum glucose were me asured at baseline and at a follow-up examination 7 years later. Blood pres sure was measured by trained observers using a random-zero sphygmomanometer . Incident hypertension was defined as an average systolic pressure of 160 mm Hg or higher and/or diastolic pressure of 95 mm Hg or higher at a single visit and/or use of antihypertensive medication during follow-up. Results: Over the 7 years of follow-up, the incidence of hypertension was 2 5.7% in the African Americans and 25.3% in the whites. Baseline plasma insu lin and insulin-to-glucose ratio were associated with an increased risk of hypertension in both the African Americans and the whites. After adjustment for age, sex, race, body mass, heart rate, and alcohol consumption at base line as well as intervention assignment in the Trials of Hypertension Preve ntion, phase 1, a 1-SD (21 pmol/mmol) difference in baseline insulin-to-glu cose ratio was associated with a 2.77 (95% confidence interval, 1.48-5.19) odds ratio of hypertension in the African Americans and a 1.69 (95% confide nce interval, 1.08-2.64) odds ratio in the whiles. Conclusion: These results suggest that higher plasma insulin levels are ass ociated with an increased risk of hypertension in both African Americans an d whites.