Coffee Drinkers Not at Increased Risk for Atrial Fibrillation

New research has cast more doubt on the theory that drinking coffee, even in large amounts, may increase the risk of developing atrial fibrillation (AF).

Analysis of 41,881 participants in the Cohort of Swedish Men (COSM) and 34,594 participants in the Swedish Mammography Cohort (SMC) found no association between coffee consumption and the 7,041 cases of incident AF that members of both groups have developed in the 12 years from baseline to the end of the study period.

The same authors then performed a complementary meta-analysis of 6 prospective studies (including the COSM and the SMC studies) and, again, found no significant different in AF risk between patients who drank coffee and those who did not.

“When we used splines to examine more extreme levels of coffee consumption, we observed no significant association in either men or women or in men and women combined,” they wrote in BioMed Central Medicine, referring to their analysis of the COSM and SMC cohorts. “The results remained essentially the same after removing those with a history of cardiac disease and/or a history of hypertension at baseline, or removing coffee abstainers.”

For patients in the COSM and SMC cohorts, information about coffee consumption came from each patient’s responses on a questionnaire, while information about AF diagnoses came from linking each study patient with records from the Swedish Hospital Discharge Record. Patients were followed from January, 1998 until death, diagnosis with AF or the end of the study period, December 31, 2009.

The meta-analysis had data on 248,910 patients from the COSM and SMC studies, 2 more Swedish studies and 2 studies from the U.S. Looked at individually, 1 of the studies found that coffee consumption was associated with a significantly lower risk of developing AF, but that study did not find any relationship between the amount of coffee consumed (above none) and AF. The other 5 studies found no significant association between coffee consumption and incident AF.

The combined results of all the studies found that people who drank the most coffee were slightly less likely to develop AF than those who drank the least, but not significantly so (relative risk, 0.96; 95% confidence interval, 0.84-1.08). Heterogeneity among the studies was moderate (I² = 60.9 %). Excluding the 1 study that did not adjust for smoking had no material impact on results. Neither did breaking the total meta-study population down by sex, by nation or by any other metric the researchers tried.

Several other recent studies have looked, without success, for links between coffee consumption and AF. Another meta-study, this 1 conducted by researchers in China found that caffeine might even reduce the risk of AF. Still, the study team from Sweden believes the issue has yet to be settled definitively.

“Although available evidence does not indicate that coffee consumption increases the risk of developing AF, coffee (or caffeine) may trigger arrhythmia [in patients who have already developed AF],” the Swedish authors wrote. “In a study of 100 patients with idiopathic paroxysmal AF, 25 patients indicated coffee consumption as a triggering factor for arrhythmia. In the COSM and the SMC, participants who had AF at baseline consumed, on average, less coffee than those without AF, suggesting that some individuals with AF may have quit drinking coffee or lowered their consumption because of an arrhythmic-triggering effect of coffee.”