Background: Cannabis use is increasing worldwide as legalization becomes more common. Prior studies have reported an association between cannabis use and increased risk of atrial fibrillation (AF). However, these have been cross-sectional and generally relied on diagnostic coding to identify cannabis users, which may not be representative of the typical recreational cannabis user. Goals: To examine the association between recreational cannabis use and AF risk. Methods: We utilized the UK Biobank, a prospective cohort study with serial assessments of lifestyle and medical diagnoses. Those who completed the cannabis use questionnaire and without prevalent AF were analyzed. Cannabis exposure was ascertained by self-reported lifetime use. AF events were identified using healthcare coding. Cox proportional hazard regression models were used to estimate the hazard ratios between the cannabis use groups and incident AF. Models were adjusted for age, sex, race, alcohol, coffee, smoking, education, and baseline cardiovascular comorbidities. Results: 157,305 participants (mean age 55.9 ± 7.7 years, 57.0% female, and 22.1% having used cannabis at least once) were followed for a mean 13.5 ± 1.7 years. Before multivariable adjustment, AF risk was found to be lower among occasional cannabis users (hazard ratio [HR] 0.71, 95% confidence interval [CI] 0.66 to 0.75, p < 0.001) and frequent cannabis users (HR 0.63, 95% CI 0.53 to 0.75, p < 0.001) compared to never users. However, after multivariable adjustment and compared to no cannabis use, neither occasional nor frequent cannabis use was associated with statistically significant differences in incident AF (HR 0.98, 95% CI 0.91 to 1.05, p = 0.58 and HR 0.98, 95% CI 0.82 to 1.18, p = 0.86 respectively) (Figure). Conclusions: Contrary to previous evidence relying on healthcare coding of cannabis use, this large prospective cohort study failed to reveal any evidence that cannabis use was associated with an increased risk of AF.
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