Residential radon exposure and incident myocardial infarction and stroke risks in the All of Us Research Program

Radon, a naturally occurring radioactive gas, is ubiquitous in the environment. Little is known about radon's impact on cardiovascular disease (CVD). This study aims to evaluate the association between residential radon exposure and incident myocardial infarction (MI) and stroke.

This cohort study included participants with electronic health records (EHR) and residential address information from the All of Us Research Program between May 31, 2017, and October 1, 2023. Residential radon exposures were estimated from a 2024 high-resolution model incorporating over six million measurements across the USA. The main outcome was MI and stroke diagnosis or condition, obtained from EHR. Stratified Cox proportional hazards regression models were used to estimate the hazard ratios (HRs) and 95% CIs for the risk of incident MI and stroke for log-2 transformed radon exposure and quartiles of radon exposure, adjusting for sociodemographic, behavioral, and clinical covariates. Sex- and smoker-stratified analyses were conducted. Penalized spline models were used to estimate the nonlinear association.

A total of 304,050 participants were included. The mean (SD) age was 58.5 (12.9) years old. Among them, 59.2% were female, 18.2% non-Hispanic Black, and 59.0% non-Hispanic White. The median radon exposure was 1.14 pCi/L (interquartile range: 0.90-1.71 pCi/L). Over 950,895 person-years, 1334 MI and 1869 stroke cases were identified. Per doubling of radon exposure was associated with increased risks for incident MI (HR = 1.46, 95% CI 1.04-2.08) and stroke (HR = 1.60, 1.02-2.49). Participants in the third and fourth quartiles had a significantly higher risk for MI and stroke compared to the lowest quartile. Specifically, the fourth quartile was associated with HR = 2.20 (95% CI 1.18-4.10) for MI and HR = 2.38 (95% CI 1.16-4.89) for stroke. Associations persisted across sexes and current smoking status. Nonlinear analyses revealed steep risk increased starting at 1 pCi/L, plateauing at 1.5 pCi/L.

In this cohort study of 304,050 participants, residential radon exposure was significantly associated with elevated risks for incident MI and stroke. Our results suggest that risks may emerge at levels well below this action level. These findings call for further research incorporating household-level exposure measures and lifetime residential histories to confirm the association.