Indoor Radon and Incident Heart Failure Among Postmenopausal Women

Importance Evidence has shown an association of radon exposure with heart failure risk factors, but whether there is an association with heart failure remains unclear. Objective To assess whether indoor radon concentrations are associated with incident heart failure among US postmenopausal women. Design, Setting, and Participants This prospective cohort study used data from the Women’s Health Initiative (WHI) observational study and clinical trials. Participants were postmenopausal women from 40 US clinical centers who were aged 50 to 79 years and did not have self-reported heart failure at enrollment or randomization (September 1993 to December 1998) but had physician adjudication of heart failure during follow-up through February 17, 2024. Exposure Geocoded participant address–based assignment of county-level, US Environmental Protection Agency–categorized indoor radon concentration (<2, 2-4, or >4 picocuries [pCi]/L). Main Outcome and Measure Incident hospitalization for acute decompensated heart failure was ascertained through physician adjudication of medical records. Hazard ratios (HRs) for heart failure by indoor radon concentration were estimated with Cox proportional hazards regression models. Results Among 43 188 postmenopausal women (mean [SD] age, 63 [7] years), 36% were exposed to a radon concentration less than 2 pCi/L; 41%, to a concentration of 2 to 4 pCi/L; and 23%, to a concentration of more than 4 pCi/L. Over a mean (SD) follow-up of 16.2 (8.4) years, 3446 incident heart failure events occurred. The fully adjusted HR for heart failure was 1.19 (95% CI, 1.07-1.33) at more than 4 pCi/L vs less than 2 pCi/L, changing little in sensitivity analyses. The HR was higher for heart failure with reduced ejection fraction (1.24; 95% CI, 1.04-1.49) and heart failure mortality (1.37; 95% CI, 1.12-1.69) at radon concentrations more than 4 pCi/L vs less than 2 pCi/L, but these HRs were not different from the null at concentrations of 2 to 4 pCi/L vs less than 2 pCi/L. The HR at concentrations greater than 4 pCi/L approximated that of a 16–mm Hg increase in systolic blood pressure or an increase of 4.8 in body mass index (calculated as weight in kilograms divided by height in meters squared). Conclusions and Relevance In this cohort study of US postmenopausal women, higher indoor radon concentrations were associated with an increased risk of incident heart failure, suggesting that radon may be a modifiable environmental determinant of heart failure.