Exploring racial disparities in CHD mortality between blacks and whites across the United States: a geographically weighted regression approach.

Coronary heart disease (CHD) mortality is one of the major contributors to racial disparities in health in the United States (US). We examined spatial heterogeneity in black-white differences in CHD mortality across the US and assessed the contributions of poverty and segregation. We used county-level, age-adjusted CHD mortality rates for blacks and whites in the continental US between 1996 and 2006. Geographically weighted regression was employed to assess spatial heterogeneity. There was significant spatial heterogeneity in black-white differences in CHD mortality (median black-white difference 17.7 per 100,000, 25th-75th percentile (IQR): 4.0, 34.0, P value for spatial non-stationarity <0.0001) before controlling for poverty and segregation. This heterogeneity was no longer present after accounting for county differences in race-specific poverty and segregation and interactions of these variables with race (median black-white difference -13.5 per 100,000, IQR: -41.3, 15.7,P value for spatial non-stationarity=0.4346). The results demonstrate the importance of spatial heterogeneity in understanding and eliminating racial disparities in CHD mortality. Additional research to identify the individual and contextual factors that explain the local variations in racial disparities is warranted.