BACKGROUND: Associations between long-term exposure to air pollution and road traffic noise have been established for ischemic heart disease, but findings have been mixed for atrial fibrillation (AF).

OBJECTIVES: The goal of the study was to examine associations of long-term exposure to road traffic noise and air pollution with AF.

METHODS: Time-varying Cox regression models were used to estimate associations of 1-, 3-, and 23-y mean road traffic noise and air pollution exposures with AF incidence in 23,528 women enrolled in the Danish Nurse Cohort (age >44y at baseline in 1993 or 1999). AF diagnoses were ascertained via the Danish National Patient Register. Annual mean weighted 24-h average road traffic noise levels (Lden) at the nurses' residences, since 1970, were estimated using the Nord2000 model, and annual mean levels of particulate matter with a diameter <2.5μm (PM2.5) and nitrogen dioxide (NO2) were estimated using the DEHM/UBM/AirGIS model.

RESULTS: Of 23,528 nurses with no prior AF diagnosis at the cohort baseline, 1,522 developed AF during follow-up. In a fully adjusted model (including PM2.5), the estimated risk of AF was 18% higher [hazard ratio (HR); 95% confidence interval (CI): 1.18; 1.02, 1.36] in nurses with residential 3-y mean Lden levels >58 dB vs. <48 dB, with similar findings for 1-y mean exposures. A 3.9-μg/m3 increase in 3-y mean PM2.5 was associated with incident AF before and after adjustment for concurrent exposure to road traffic noise (HR 1.09; 95% CI: 1.00, 1.20 and 1.08; 95% CI: 0.97, 1.19, respectively). Associations with 1-y mean PM2.5 exposures were positive but closer to the null and not significant. Associations with NO2 were null for all time periods before and after adjustment for road traffic noise and inverse when adjusted for concurrent PM2.5.

CONCLUSION: Our analysis of prospective data from a cohort of Danish female nurses followed for up to 14 y provided suggestive evidence of independent associations between incident AF and 1- and 3-y exposures to road traffic noise and PM2.5. https://doi.org/10.1289/EHP8090.