Secondhand tobacco exposure and risk of atrial fibrillation: a systematic review

This systematic review aims to provide evidence from current observational studies on whether Secondhand smoke (SHS) exposure is associated with increased risk of atrial fibrillation (AF) risk, so to identify potential high-risk subgroup to inform both mechanistic hypotheses and prevention strategies. A systematic screening of the PubMed, EMBASE and Cochrane Central databases was conducted until September 2025 to identify observational studies focused on the association between SHS and AF. Six observational studies involving more than 420,000 participants were included. Early-life SHS exposure, including gestational and childhood household exposure, was consistently associated with a higher risk of AF in adulthood. Evidence for adulthood SHS exposure was more heterogeneous; however, studies incorporating objective biomarkers or dose–response assessments demonstrated clearer associations. Several studies reported stronger associations among women, Black individuals, never-smokers, and those with elevated genetic susceptibility. Notably, a large population-based cohort demonstrated a graded relationship between SHS exposure and incident AF, with evidence of gene–environment interaction. Available evidence suggests that SHS exposure, particularly during early life, may be associated with an increased risk of AF. The observed heterogeneity by exposure window, assessment method, and population subgroup underscores the importance of life-course and equity-focused approaches to AF prevention. Reducing SHS exposure may represent a modifiable and underrecognized strategy for long-term AF risk reduction.