Association between Hyperinsulinemia and Hypertension among White, Black, and Mexican American Adults. Results from the Third National Health and Nutrition Examination Survey, 1988-1994.
Objective: To examine the association between hyperinsulinemia and blood pressure independent of body mass among nondiabetic white non-Hispanic, black non-Hispanic, and Mexican American adults. Methods: We examined this relationship using data from 8004 adults aged ≥20 years from the Third National Health and Nutrition Examination Survey (1988-1994). Univariate differences in body mass index (BMI), waist-to-hip ratio (WHR), glycosylated hemoglobin (HbA 1c ), fasting plasma glucose and C-peptide were examined between normotensives and hypertensives within each racial or ethnic group. Logistic regression was used to obtain the likelihood of being hypertensive across race specific tertiles of C-peptide adjusting for age, sex, education, BMI, and WHR. Results: The prevalence of hypertension was 21.1% among whites, 24.6% among blacks, and 10.9% among Mexican Americans. Hypertensives were older, with higher BMI, WHR, HbA 1c , fasting plasma glucose, and fasting C-peptide levels than normotensives. Also, the prevalence of hypertension increased significantly with C-peptide level for each of the racial or ethnic groups. Persons with a C-peptide in the upper tertile were more likely to be hypertensive than those with a C-peptide level in the lower tertile after adjustment for age, sex, education, and BMI (Mexican Americans OR=3.3, 95% CI=2.2-4.8; whites OR=2.0, 95% CI=1.5-2.7, blacks OR=2.0, 95% CI=1.3-3.0). Adjustment for WHR attenuated the association between C-peptide and hypertension (Mexican Americans OR=3.0, 95% CI=2.0-4.5; whites OR=1.6,95% CI=1.2-2.2; blacks OR=1.7, 95% CI=1.1-2.6). Conclusion: These results suggest that hyperinsulinemia is associated with hypertension independent of BMI and diabetes. Further, WHR was identified as a confounder and should be taken into account in addition to BMI when evaluating the relationship between C-peptide and hypertension.