Importance: Socioeconomically disadvantaged subpopulations are more vulnerable to fine particulate matter (PM_2.5) exposure. However, as prior studies focused on individual-level socioeconomic characteristics, how contextual deprivation modifies the association of PM_2.5 exposure with cardiovascular health remains unclear.

Objective: To assess disparities in PM_2.5 exposure association with cardiovascular disease among subpopulations defined by different socioeconomic characteristics.

Design, Setting, and Participants: This cohort study used longitudinal data on participants with electronic health records (EHRs) from the All of Us Research Program between calendar years 2016 and 2022. Statistical analysis was performed from September 25, 2023, through February 23, 2024.

Exposure: Satellite-derived 5-year mean PM_2.5 exposure at the 3-digit zip code level according to participants’ residential address.

Main Outcome and Measures: Incident myocardial infarction (MI) and stroke were obtained from the EHRs. Stratified Cox proportional hazards regression models were used to estimate the hazard ratio (HR) between PM_2.5 exposure and incident MI or stroke. We evaluated subpopulations defined by 3 socioeconomic characteristics: contextual deprivation (less deprived, more deprived), annual household income (≥ 50,000 USD, < 50,000 USD), and race and ethnicity (non-Hispanic Black, non-Hispanic White). We calculated the ratio of HRs (RHR) to quantify disparities between these subpopulations.

Results: A total of 210 554 participants were analyzed (40% age >60 years; 59.4% female; 16.7% Hispanic, 19.4% Non-Hispanic Black, 56.1% Non-Hispanic White, 7.9% other [American Indian, Asian, more than 1 race and ethnicity]), among whom 954 MI and 1407 stroke cases were identified. Higher PM_2.5 levels were associated with higher MI and stroke risks. However, disadvantaged groups (more deprived, income <$50 000 per year, Black race) were more vulnerable to high PM_2.5 levels. The disparities were most pronounced between groups defined by contextual deprivation. For instance, increasing PM_2.5 from 6 to 10 μg/m3, the HR for stroke was 1.13 (95% CI, 0.85-1.51) in the less-deprived vs 2.57 (95% CI, 2.06-3.21) in the more-deprived cohort; 1.46 (95% CI, 1.07-2.01) in the $50 000 or more per year vs 2.27 (95% CI, 1.73-2.97) in the under 50,000 USD per year cohort; and 1.70 (95% CI, 1.35-2.16) in White individuals vs 2.76 (95% CI, 1.89-4.02) in Black individuals. The RHR was highest for contextual deprivation (2.27; 95% CI, 1.59-3.24), compared with income (1.55; 95% CI, 1.05-2.29) and race and ethnicity (1.62; 95% CI, 1.02-2.58).

Conclusions and Relevance: In this cohort study, while individual race and ethnicity and income remained crucial in the adverse association of PM_2.5 with cardiovascular risks, contextual deprivation was a more robust socioeconomic characteristic modifying the association of PM_2.5 exposure.