Caffeine Not Associated With Increased Risk of Atrial Fibrillation

Laurie Barclay, MD

March 10, 2005

March 10, 2005 — Caffeine does not increase the risk for developing atrial fibrillation, according to the results of a prospective study published in the March issue of the American Journal of Clinical Nutrition.

"Caffeine toxicity by self-intended poisoning produces tachyarrhythmias such as supraventricular tachycardia, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation," write Lars Frost and Peter Vestergaard, from Aarhus University Hospital in Denmark. "The risk of cardiac arrhythmias associated with customary daily consumption of caffeine from coffee, tea, cola, cocoa, and chocolate does not seem to be increased at the ventricular level, but more information is needed about what happens at the supraventricular level (i.e, the atrium)."

Investigators in the Danish Diet, Cancer, and Health Study evaluated the association between the risk of atrial fibrillation or flutter and daily consumption of caffeine from coffee, tea, cola, cocoa, and chocolate in 47,949 subjects with a mean age of 56 years.

During a mean follow-up of 5.7 years, 555 participants (373 men and 182 women) developed atrial fibrillation or flutter. Caffeine consumption was not associated with risk of atrial fibrillation or flutter. Using the lowest quintile of caffeine consumption as a reference, the adjusted hazard ratios in quintiles 2, 3, 4, and 5 were 1.12 (95% confidence interval [CI] 0.87 - 1.44), 0.85 (95% CI, 0.65 - 1.12), 0.92 (95% CI, 0.71 - 1.20), and 0.91 (95% CI, 0.70 - 1.19), respectively.

Study limitations include the possibility of biased follow-up, limited statistical power, inclusion only of atrial fibrillation or flutter that was symptomatic and that led to hospitalization or clinical investigation in an outpatient hospital clinic, reliance on self-reported data on the consumption of caffeine-containing food and drink items, no information on supplementary intake of caffeine from drugs, and the possibility of unmeasured bias and uncontrolled confounding.

"Some clinicians advise patients with cardiac arrhythmias to avoid caffeine-containing beverages such as coffee and tea," the authors write. "In this large cohort study, we could not find evidence for such a practice."

The Danish Medical Research Council supported this study. Dr. Frost has received funding and grant support for research projects from Aarhus University, Boehringer-Ingelheim, Cardiome Pharma, the Danish Heart Foundation, the Danish Medical Research Council, the Danish Society of Nephrology, the Hørslev Foundation, Laerdahls Foundation for Acute Medicine, Lægekredsforeningens Forskningsfond, Merck Sharp & Dome, Nycomed, and Pfizer, and he has served as a consultant for AstraZeneca and Pfizer.

In an accompanying editorial, Martijn B. Katan and Evert Schouten, from the Wageningen Centre for Food Sciences and Wageningen University in the Netherlands, note that "many ills have been ascribed to caffeine, but few have been substantiated."

They support the study methodology and the investigators' conclusions, although they point out that the study provides no information about zero intake of coffee. Although it is therefore possible that total abstinence from caffeine reduces the incidence of atrial fibrillation, the lack of an association over the wide range of reported intakes makes that possibility less plausible.

"The caffeine in coffee does cause an increase of 2.4 mm Hg in systolic blood pressure when 5 cups are consumed daily," Drs. Katan and Schouten write. "That effect is enough to justify counseling high-risk patients to moderate their caffeine intake, but other interventions — eg, smoking cessation, weight loss, exercise, and a healthy diet low in saturated and trans fats — yield larger benefits and should come first."

The Wageningen Centre for Food Sciences, an alliance of major Dutch food industries, TNO Nutrition and Food Research, Wageningen University and Research Centre, Maastricht University, and the Dutch government supported this study. Dr. Katan previously received grants from the Institute for Scientific Information on Coffee and from Nestlé to study health effects of coffee.

Am J Clin Nutr. 2005;81:578-582

Reviewed by Gary D. Vogin, MD

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