Abstract MP19: Indoor Radon Concentrations Are Associated With Incident Myocardial Infarction in the Women’s Health Initiative

Background: Radon is an emerging risk factor for stroke, but its relationship with common forms of coronary heart disease (CHD) is unclear. Methods: We studied the radon-myocardial infarction (MI) association among US women without a history of MI or coronary revascularization at the 1993-1998 screening visit of the Women’s Health Initiative Clinical Trials (CT) and Observational Study (OS). We paired their geocoded addresses with county-level, indoor, screening radon gas concentrations predicted by the US Environmental Protection Agency and classified as Zone 3 (<2 pCi/L), Zone 2 (2-4 pCi/L), or Zone 1 (>4 pCi/L). We used medical records to identify incident, physician-reviewed, classified, and adjudicated MI through 02/17/24 based on acute onset of cardiac pain, electrocardiographic abnormalities, and/or elevated cardiac biomarkers. We estimated the radon-MI association as a hazard ratio (HR) and 95% confidence interval (CI) using a Cox proportional hazards model on an attained-age scale adjusting for CT/OS membership, race/ethnicity, education, homemaker status, US Census region, neighborhood socioeconomic status, annual mean concentration of ambient particulate matter <2.5 um in diameter (PM 2.5 , ug/m 3 ), smoking, alcohol intake, sodium intake (g/day), Healthy Eating Index, recreational physical activity (metabolic equivalent-hr/wk), body mass index (kg/m 2 ), systolic blood pressure (mm Hg), as well as history of diabetes and hypercholesterolemia. Results: Among 153,701 postmenopausal women examined at 40 US centers (mean age = 63.1 years; 83% white; 9% Black; 4% Hispanic/Latina; 4% other), we identified 5,925 incident MIs over a mean follow-up of 13.2 years. Incidence proportions and corresponding rates in Radon Zones 3, 2, and 1 were 36, 38, and 43 MIs per 10 3 women at risk and 278, 287, and 314 MIs per 10 5 woman-years, respectively. Relative to women in Zone 3, those in Zones 2 and 1 had higher hazards of incident MI: HR (95% CI) = 1.04 (0.97-1.11) and 1.18 (1.09-1.28). The association was robust after adjusting for center-level confounding, multiply imputing missing data, stratifying by smoking or PM 2.5 , and substituting related radon exposures and CHD outcomes. In contrast, it was attenuated after replacing MI with a negative outcome control, coronary revascularization. Conclusion: Exposure to radon gas—a residentially ubiquitous carcinogen previously associated with risk of stroke—may also be associated with risk of MI among postmenopausal women.