Impact of air pollution and multimorbidity on the risk of incident atrial fibrillation

Background Emerging evidence suggests associations between air pollution, multimorbidity, and atrial fibrillation (AF), but their interplay remains unclear. We evaluated these relationships in a prospective cohort. Methods We retrieved a total of 480 344 individuals from the UK Biobank. The quantification of air pollutants (particulate matter with a diameter ≤2.5 μm (PM 2.5 ), particulate matter with a diameter ≤10 μm (PM 10 ), nitrogen oxides (NO x ) and nitrogen dioxide (NO 2 )) was conducted at the geocoded residential locations of each participant. Multimorbidity clusters were determined using latent class analysis using 35 long-term conditions (LTCsc. Three latent classes were identified: non-cardiovascular disease (non-CVD) multimorbidity, mental health multimorbidity and cardiometabolic multimorbidity. These were compared with no LTCs and singular LTCs. Cox models examined the effects of air pollution and multimorbidity status on AF incidence. Counterfactual analyses were performed to calculate the proportion of preventable AF. Results During a median follow-up of 12.5 years (IQI 11.8 to 13.2), 28 977 incident AF cases occurred. Exposure to PM 2.5 was associated with a 37% higher AF risk per 1 µg/m³ higher PM 2.5 (HR 1.37, 95% CI 1.36 to 1.38), with similar patterns for PM 10 (HR 1.18, 95% CI 1.17 to 1.18), NOₓ (HR 1.06, 95% CI 1.06 to 1.06) and NO 2 (HR 1.03, 95% CI 1.03 to 1.03). Compared with no multimorbidity, cardiometabolic multimorbidity showed a 1.84-fold higher AF risk (95% CI 1.76 to 1.93), while non-CVD multimorbidity showed a 2.13-fold higher risk (95% CI 1.97 to 2.30). Additive interactions were observed between air pollution and multimorbidity. For example, participants with high PM 2.5 exposure and non-CVD multimorbidity had a sixfold higher AF risk (95% CI 5.25 to 6.82; relative excess risk due to interaction (RERI) 2.31, 95% CI 1.55 to 3.07), exceeding the sum of individual risks. Counterfactual analysis suggested that reducing PM 2.5 to the 10th percentile could prevent 26–52% of AF cases in multimorbidity subgroups, with the largest reductions in cardiometabolic (52%) clusters. Conclusion Air pollution and multimorbidity were independently and synergistically associated with higher AF risk. Mitigation strategies targeting pollution may reduce AF burden, particularly in high-risk populations.