IS HYPERTENSION MORE SEVERE AMONG US BLACKS, OR IS SEVERE HYPERTENSION MORE COMMON

It is frequently stated that the risk of sequelae from hypertension at a given level of severity is higher among blacks than whites, althoug h little empirical evidence supports that supposition. In this work we examined the basis for accepting the existence of a black:white diffe rential in hypertension outcomes in a representative biracial sample o f the U.S. population followed in the First National Health and Nutrit ion Examination Survey (NHANES-I) Epidemiologic Follow-up Study. As we ll recognized, the risk associated with increasing blood pressure is n ot dichotomous but varies across the entire distribution in a curvilin ear fashion. The rightward skew of the blood pressure distribution wit h increasing mean levels affects comparisons between Populations, sinc e the change in shape results in a change in the mix of case severity. These considerations can influence estimates of the relative populati on-attributable risk from hypertension, considered as a dichotomous cl assification in blacks and whites. Although the relative risk of death associated with a systolic blood pressure of greater than or equal to 140 mmHg in this study was higher for blacks than for whites (1.7 and 1.5, respectively), with all-cause mortality as the outcome, the logi stic coefficient for systolic blood pressure was not significantly dif ferent among white as compared with black men (beta = 0.016 us. 0.010; p = 0.320 for race interaction term) and was slightly greater among w hite vs. black women (beta = 0.013 vs. 0.010; P = 0.05). After strata- specific blood pressure adjustment, the principal determinant of incre ased population risk for both black men and women was the higher preva lence of hypertension, not differential severity. The population-attri butable risk for hypertension was at least two times higher among blac ks because of the higher prevalence among them; moreover, the increase d prevalence accounted for 10% of the interethnic difference in mortal ity. Data from this study indicate that hypertension was not more seve re among individual blacks, simply more common in the population.