Environment/Climate Change
Radon exposure and cognitive impairment Yijia Zhang* Yijia Zhang Zhang Zhang Zhang Zhang Columbia University Irving Medical Center
Background Ionizing radiation exposure may contribute to cognitive impairment. Radon is a ubiquitous radioactive gas that can expose the brain to low-dose radiation, but evidence linking radon exposure to cognitive outcomes remains limited.
Methods We included 24,652 participants from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study who were free of baseline cognitive impairment and stroke and had complete exposure and outcome data. Radon exposure was assigned using monthly ZIP Code–level estimates generated via machine learning, with radon level at enrollment used as the exposure. Radon was analyzed as a binary variable using a cutoff of 2 pCi/L, corresponding to the US Environmental Protection Agency–recommended level at which mitigation should be considered. Global cognitive status was assessed using the Six-Item Screener (SIS). Cognitive impairment was defined as either a SIS score <4 on the most recent assessment or in a sensitivity analysis SIS scores <4 on the 2 most recent assessments. Associations were estimated using ORs with 95% CIs.
Results Approximately 9.3% of participants resided in ZIP codes with radon levels ≥2 pCi/L. After adjustment for demographic, socioeconomic, lifestyle, and health factors, radon exposure was not associated with cognitive impairment overall in this predominantly low-radon cohort. However, smoking status modified the association. Among never smokers, radon exposure ≥2 pCi/L was associated with increased odds of cognitive impairment defined by the most recent SIS <4 (OR, 1.26; 95% CI, 1.05–1.50) and by SIS <4 on the 2 most recent assessments (OR, 1.35; 95% CI, 1.05–1.75). No associations were observed among ever smokers.
Conclusion In a large population predominantly residing in low-radon regions, radon exposure ≥ 2 pCi/L was associated with cognitive impairment among never smokers but not ever smokers. Further studies are needed to clarify potential confounding, particularly from competing risks.