Hypertension as a cause of lower than expected death rates from coronary artery disease among blacks

Coronary risk factors are more prevalent among blacks than whites in the United States. It is therefore paradoxical that age-adjusted death rates for coronary artery disease (CAD) are similar in the two racial groups. The major risk factor for CAD that is more common among blacks than whites is hypertension, which increases the risk of CAD by two- to fourfold, depending on the presence of smoking, hypercholesterolemia, or other factors. Two general hypotheses have been advanced to explain the lower than expected CAD rates among blacks: (1) the presence of some protective factors, such as increased levels of high density lipoprotein cholesterol (HDL); or (2) selective loss of CAD-prone black individuals due to other causes of mortality. Analysis of age-specific death rates from the vital statistics records strongly suggests that differential survival in the black and white populations, i.e., mortality selection, is the primary explanation of this phenomenon. We sought to test this hypothesis by examining an entirely independent data base. Data from the National Hospital Discharge Survey for the years 1973–1984 were evaluated to determine whether there were age-related differences in case-fatality rates between whites and blacks, and whether a crossover pattern in mortality could be discerned. The results demonstrate that in-hospital case-fatality rates for acute myocardial infarction (MI) were 10% to 70% higher for each of the 10-year age groups for blacks up to age 70 years, at which time a crossover occurred. The median age at which death due to MI occurred in blacks was approximately 5 years earlier than in whites. We conclude that CAD has an earlier onset in blacks and is more severe at any given age under 70 years, and that age-adjusted CAD rates are reduced by the effects of mortality selection on a cohort. The primary cause of non-CAD cardiovascular death among blacks is hypertension. Thus, the relatively increased prevalence of hypertension among blacks is paradoxically the cause of the lower than anticipated CAD death rates.