Associations Between Residential Greenspace, Socioeconomic Status, and Stroke: A Matched Case-Control Study.

Purpose: Studies have shown increased residential greenspace is associated with improved outcome following stroke. This study sought to determine if residential greenspace is an independent stroke risk factor.

Methods: A retrospective 1:4 matched case-control study involving 1174 stroke and 4696 control patients over a 3-year period from Milwaukee County, Wisconsin, was conducted. Greenspace was determined using normalized difference vegetation index (NDVI) for a 250-meter radius surrounding a subject's residence. The area deprivation index (ADI) for the census block tract of a subject's residence was obtained from the Neighborhood Atlas (University of Wisconsin School of Medicine and Public Health). Relationship between greenspace, ADI, and stroke was determined using conditional logistic regression. Relationships among NDVI, state and national ADI, and proximity to public parks were determined using Spearman's rank-order correlation.

Results: NDVI and stroke risk were inversely correlated (odds ratio [OR]: 0.33, 95% CI: 0.111-0.975; P=0.045), with 19% lowered odds of stroke for patients living in the highest greenspace quartile compared to the lowest quartile (OR: 0.81, 95% CI: 0.672-0.984; P=0.045). Patients living in the most deprived ADI quartile had 28% greater stroke risk than those living in the least deprived ADI quartile (OR: 1.28, 95% CI: 1.02-1.6; P=0.029). Non-Hispanic Black patients lived in residential areas with lower greenspace (P<0.001) and neighborhoods of greater state and national ADI (P<0.001 for both) than non-Hispanic White patients.

Conclusions: In Milwaukee County, living with greater surrounding greenspace or areas of lower deprivation is associated with lower odds of stroke. NDVI represents an independent risk factor for stroke, not simply a proxy for socioeconomic status.