BackgroundEfforts to reduce socioeconomic inequities in cardiovascular disease include interventions to change the built environment. We aimed to explore whether socioeconomic inequities in coronary heart disease (CHD) incidence are ameliorated or exacerbated in environments supportive of physical activity (PA).MethodsWe used data from the Reasons for Geographic and Racial Differences in Stroke study, which recruited US residents aged 45 or older between 2003 and 2007. Our analyses included participants at risk for incident CHD (n=20 808), followed until 31 December 2014. We categorised household income and treated it as ordinal: (1) US$75 000+, (2) US$35 000–US$74 000, (3) US$20 000–US$34 000 and (4) <US$20 000. We operationalised PA-supportive environments using characteristics within a 1 km residential buffer: walkable destinations density, PA facility density and proportion green land cover. We used Cox proportional hazards models to estimate the adjusted association of income with incident CHD, and tested effect modification by PA-supportive environment variables.ResultsWe found a 25% (95% CI 1.17% to 1.34%) increased hazard of CHD per 1-category decrease in household income category. Adjusting for PA-supportive environments slightly reduced this association (HR=1.24). The income–CHD association was strongest in areas without walking destinations (HR=1.57), an interaction which reached statistical significance in analyses among men. In contrast, the income–CHD association showed a trend towards being strongest in areas with the highest percentage of green land cover.ConclusionsIndicators of a PA supportive environment show divergent trends to modify socioeconomic inequities in CHD . Built environment interventions should measure the effect on socioeconomic inequities.