Insulin sensitivity and blood pressure in a biethnic sample: The Miami Community Health Study

An association between blood pressure and insulin sensitivity among normotensive African-Americans has not been demonstrated consistently in epidemiologic studies. Part of the discrepancy may be due to studying persons with profound obesity - an insulin-resistant state itself. The association between insulin-mediated glucose uptake (i.e., insulin sensitivity) and blood pressure was examined among 25 nondiabetic African-American and 28 white non-Hispanic persons aged 25-44 years who ranged from normal weight to obese, using the hyperinsulinemic euglycemic clamp technique. In bivariate analyses, insulin sensitivity was inversely related to systolic (P < 0.01) and diastolic blood pressure (P = 0.08) among African-American persons and to diastolic blood pressure among white non-Hispanic subjects (p < 0.05). Covariate adjustment for age and sex had only a marginal effect on these results. When the data were pooled and further adjusted for ethnicity, insulin sensitivity remained significantly associated with both systolic and diastolic blood pressure (P < 0.01 for each). To consider the effect of obesity, body mass index (BMI) was divided at the sample median (26.5 kg/m²) and the analyses were repeated within each stratum. Among those whose BMI was below the median value, each increment in insulin sensitivity was associated with a 2-mmHg decrease in systolic blood pressure (P = 0.02). These results suggest that ethnicity was not a strong effect modifier in this sample and indicated that insulin sensitivity was inversely related to blood pressure level in these normotensive African-American and white, non-Hispanic participants.