Relative Versus Absolute Neighborhood Economic Conditions And Risk Of Stroke In A United States National Cohort

Introduction: Neighborhood economic conditions are important predictors of incident stroke. Neighborhood economic conditions can be characterized differently but studies have not identified which characterizations are most predictive of incident stroke. Previous work has suggested that the income distribution within the population may be more relevant for chronic disease than the absolute value of median income of the population. This project aims to estimate the effects of neighborhood income and neighborhood income inequality on incidence stroke. Hypothesis: Neighborhood income inequality and absolute neighborhood income will predict incident stroke above and beyond demographic characteristics and individual socioeconomic status. Methods: We used data from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study, a national longitudinal study of black and white older adults (N=29,443). Baseline median household income and the Gini coefficient of income inequality at the Census Tract level were obtained from the 2000 decennial census. Both variables were standardized to have a mean of 0 and a standard deviation of 1; z-score of median household income was multiplied by -1 (representing neighborhood income deprivation) to allow for comparability. Using Cox Proportional Hazards analysis we examined the risk of stroke associated with these exposures in separate models. Model 1 was unadjusted, Model 2 was adjusted for demographic characteristics (age, race, sex, marital status), and Model 3 was adjusted for individual socioeconomic characteristics (household income and education). Results: Within Model 1, neighborhood income deprivation (HR: 1.18; 95% CI 1.11-1.24) and neighborhood income inequality (HR: 1.10; 95% CI: 1.05-1.16) were both significantly associated with risk of stroke. The association persisted in Model 2: neighborhood income deprivation (HR: 1.13; 95% CI 1.07-1.20) and neighborhood income inequality (HR: 1.06; 95% CI: 1.00-1.11). Within Model 3, neighborhood income deprivation maintained its positive association (HR: 1.06; 95% CI 1.00-1.13), while neighborhood income inequality was no longer predictive of stroke risk (HR:1.04; 95% CI 0.99-1.10). Conclusions: Neighborhood income deprivation and neighborhood income inequality were similar predictors of incident stroke. The effect of absolute economic resources in a Census Tract was slightly larger than the relative economic standards within a Census Tract. There is a need to investigate other characterizations of neighborhood economic conditions, such as residential income segregation. The findings from this project suggest that there are multiple policy levels that can be used to decrease incident stroke, through decreasing income inequality and improving the absolute economic conditions of deprived neighborhoods.