Regional Differences in African Americans' High Risk for Stroke: The Remarkable Burden of Stroke for Southern African Americans
Introduction
The “STROKE BELT” was first identified in 1965 as a region with approximately 50% higher stroke mortality rates in the southeastern United States (1). While there are different definitions of the region, it frequently includes 8 southern states: North Carolina, South Carolina, Georgia, Tennessee, Mississippi, Alabama, Louisiana, and Arkansas. Although this region of excess stroke mortality rate has been persistent and very well documented 1, 2, 3, 4, 5, 6, 7, the contributing causes have remained a mystery with at least 10 hypothesized potential contributing causes 8, 9. As there are limited national data on stroke incidence, it is not clear whether the excess in stroke mortality is primarily associated with higher stroke incidence or case fatality following stroke events 8, 9. Within the “STROKE BELT,” a “Buckle” region along the coastal plain of North Carolina, South Carolina, and Georgia has even higher stroke mortality (approximately twice the national rate) 4, 5.
In addition, stroke mortality rates are approximately 50% higher in African Americans than in whites, with a larger difference at younger ages; at 55 years of age, the risk of dying from stroke is 3 times greater for blacks than whites 10, 11, 12, 13. Data from the Greater Cincinnati/Northern Kentucky Stroke Study suggest the excess mortality rate is primarily attributable to higher incidence of stroke (rather than higher case fatality) among African Americans (14). As with the excess stroke mortality in the Southeast, the known contributing factors for the excess stroke mortality in blacks (primarily higher prevalence of hypertension and diabetes and a lower socioeconomic status) explain only a fraction of the overage 15, 16, 17.
The geographic variations in overall stroke mortality risk raise the question whether there are also variations in the black-to-white ratio of stroke mortality (13). That is, in a comparison of African Americans and whites by state or region, does the relative excess of stroke mortality among African Americans vary? Are there regions where the black-to-white stroke mortality ratio is even greater than the national average?
Previously we noted differences in the age-adjusted black-to-white stroke mortality ratio (without stratification by age) among the states. For example, in Florida African Americans have 1.92 times the rate of whites, whereas in New York African Americans have 1.06 times the rate of whites (13). In this report we explore age-specific black-to-white mortality ratios for each sex by state and by aggregations of states classified as nonsouthern or southern.
Section snippets
Methods
State stroke mortality rates were calculated for sex and age strata (45–54 years, 55–64, 65–74, 75–84, and 85 or older) on the basis of US vital statistics 1997 to 2001 (18) and a population estimate from the midpoint of 1999 (19). Stable estimates of stroke mortality ratios require a substantial population in each group of interest. All 50 states have sufficient numbers of white residents to provide stable estimates, but 24 states have a small African American population, so our analysis had
Results
Age-specific white and African American stroke mortality rates and the age-specific black-to-white mortality ratio are in Tables 1A (men) and 1B (women). Review of the black-to-white mortality ratios shows a clear pattern, with southern states having greater values than nonsouthern states. The geographic differences in the distributions of stroke mortality ratios by groups of states are shown in Fig. 1, A and B.
A pattern of declining black-to-white mortality ratios with increasing age is
Discussion
Except at the oldest ages, African Americans are at higher risk of death from stroke than are whites, a finding that held in all the states we studied. The excess in stroke mortality for nonsouthern African Americans is substantial: for men there was an average black-to-white stroke mortality ratio across nonsouthern states of 2.76 (1.04/0.38) at age 55 to 64; 1.81 (2.49/1.37) at age 65 to 74; and 1.22 (5.89/4.80) at age 75 to 84. Similar excesses were found for women. However, this report
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