Objective To assess alcohol intake as a risk factor for adverse events among patients with incident atrial fibrillation (AF).

Design Prospective cohort study.

Setting Population based cohort study and nationwide Danish registries.

Patients The Danish Diet, Cancer and Health study included 57 053 participants (27 178 men and 29 875 women) aged between 50 and 64 years. The study population for this study included the 3107 participants (1999 men, 1108 women) who developed incident AF after inclusion.

Main outcome measures A composite of thromboembolism or death.

Results During a median follow-up of 4.9 years 608 deaths and 211 thromboembolic events occurred. Of those who developed AF, 690 (35%) men and 233 (21%) women had a high intake of alcohol (>20 drinks/week for men and >13 drinks/week for women). After adjustment for use of oral anticoagulation and components of the CHA₂DS₂-VASc score, men with an intake of >27 drinks/week had a higher risk for thromboembolism or death (hazard ratio (HR) 1.33, 95% CI 1.08 to 1.63) than men with an intake of <14 drinks/week. Women with an intake of >20 drinks/week also had a higher risk (HR 1.23, 95% CI 0.78 to 1.96) than women in the low intake category. The higher risk among men was primarily driven by mortality (HR 1.51, 95% CI 1.20 to 1.89), whereas the risk found among women was driven by thromboembolism (HR 1.71, 95% CI 0.81 to 3.60).

Conclusions High alcohol intake predicts thromboembolism or death, even after adjustment for established clinical risk factors, and may help identify high risk AF patients who could be targeted for stroke and cardiovascular prevention strategies.