Indoor radon exposure and COPD in never smokers: a case–control study in a radon-prone area in Spain

Previous studies have linked radon exposure with mortality in patients with chronic obstructive pulmonary disease (COPD), but there is little data assessing the role of indoor radon exposure with the risk of COPD or its severity in never smokers. Objective: To explore whether indoor radon exposure is associated with the risk or severity of COPD in never smokers. Multicentric, hospital-based, case–control study, located in Northwest Spain. The study included 300 never-smokers with COPD (cases) and 462 never smoking controls. COPD cases and their severity were included following Global Initiative for Obstructive Lung Disease 2019 (GOLD) criteria for COPD diagnosis. Radon concentrations were measured in each participant’s home using long-term (at least 3 months) alpha-track devices. Results were analyzed for cases and controls, and also for different lengths of residence in the last dwelling employing logistic regression. For cases, hospital admissions in the last 3 years due to COPD exacerbations and COPD severity were related to radon concentrations. (1) Indoor radon exposure was similar in cases and controls, but radon exposure showed a statistically significant association with COPD when length of residence in the same dwelling was > 40 years. There was an odds ratio (OR) of 2.79 (1.06–7.40) for those with highest (> 300 Bq/m 3 ) vs. lowest radon exposure (< 100 Bq/m 3 ); (2) in cases, the severity of airflow obstruction increased with higher indoor radon exposure, and the proportion of COPD cases with radon exposure above 300 Bq/m 3 was higher in GOLD 4 (50%) vs. GOLD 1 (9%). Although indoor radon exposure was not higher in cases compared to controls, the association increased for those with higher exposures who lived for longer periods in the same dwelling, reaching statistical significance when length of residence was higher than 40 years. In COPD cases, higher radon exposure was associated with more severe airflow limitation.