Associations of hyperinsulinemia and hypertension independent of body mass among white, black, and Mexican-American adults without diabetes.

Objective: In a cross-sectional study, we examined the association between hyperinsulinemia and hypertension, independent of body mass, among White non-Hispanic, Black non-Hispanic, and Mexican-American adults without diabetes.

Methods: Data are from 8,004 adults, aged > or = 20 years from the Third National Health and Nutrition Examination Survey, 1988-1994. Univariate differences in C-peptide levels (fasting) were examined in normotensives and hypertensives by racial or ethnic group. Multivariate logistic regression models were used to estimate the likelihood of hypertension across race-specific tertiles of C-peptide levels. Adjustments were made for age, sex, education, body mass index, and waist-to-hip ratio.

Results: The prevalence of hypertension was 21.1% among non-Hispanic Whites, 24.6% among non-Hispanic Blacks, and 10.9% among Mexican Americans. The prevalence of hypertension increased significantly with C-peptide level for each racial or ethnic group. Mexican Americans with a C-peptide level in the upper tertile were 3.3 times (95% confidence interval [CI]=2.2-4.8) more likely to have hypertension than those with a C-peptide level in the lower tertile, after adjustment for age, sex, education, and BMI. Further adjustment for WHR resulted in a slightly lower odds ratio (OR=3.1; 95% CI=2.0-4.6). Among non-Hispanic Whites and Blacks, respectively, persons with a C-peptide level in the upper tertile were 1.6 times (95% CI=1.2-2.2) and 1.7 times (95% CI=1.1-2.6) more likely to have hypertension than those with a C-peptide level in the lower tertile, after multivariate (including WHR) adjustment.

Conclusions: These data suggest that high C-peptide levels, reflecting endogenous insulin secretion, are associated with hypertension, independent of body mass index and diabetes. This association was strongest among Mexican Americans. Our results also suggest that adjustment for waist-to-hip ratio as a confounding factor may be important in evaluation of the relationship between C-peptide level and hypertension.