Background: It is somewhat controversial whether caffeine consumption is associated with an increased risk of developing atrial fibrillation (AF).
Objective: We prospectively assessed the relation between caffeine intake and incident AF.
Design: A total of 33,638 initially healthy women who participated in the Women's Health Study and who were gt 45 y of age and free of cardiovascular disease and AF at baseline were prospectively followed for incident AF from 1993 to 2 March 2009. All women provided information on caffeine intake via food-frequency questionnaires at baseline and in 2004.
Results: During a median follow-up of 14.4 y (interquartile range: 13.8-14.8 y), 945 AF events occurred. Median caffeine intakes across increasing quintiles of caffeine intake were 22, 135, 285, 402, and 656 mg/d, respectively. Age-adjusted incidence rates of AF across increasing quintiles of caffeine intake were 2.15, 1.89, 2.01, 2.24, and 2.04 events, respectively, per 1000 person-years of follow-up. In Cox proportional hazards models updated in 2004 by using time-varying covariates, the corresponding multivariable-adjusted hazard ratios (95% CI) were 1.0, 0.88 (0.72, 1.06), 0.78 (0.64, 0.95), 0.96 (0.79, 1.16), and 0.89 (0.73, 1.09) (P for linear trend: 0.45). None of the individual components of caffeine intake (coffee, tea, cola, and chocolate) were significantly associated with incident AF.
Conclusions: In this large cohort of initially healthy women, elevated caffeine consumption was not associated with an increased risk of incident AF. Therefore, our data suggest that elevated caffeine consumption does not contribute to the increasing burden of AF in the population. This trial was registered at clinicaltrials.gov as NCT00000479.