New Study Casts More Doubt on Negative Link Between Coffee Intake and Risk of Arrhythmia

Habitual coffee drinkers, including those who are genetically predisposed to metabolize caffeine differently, were not at a heightened risk of developing cardiac arrhythmias in a large cohort study published July 19, 2021, in JAMA Internal Medicine.

“Most research exploring the associations between coffee and arrhythmias has relied on self-reported coffee consumption,” wrote study authors led by Gregory Marcus, MD, professor of medicine, Division of Cardiology, University of California San Francisco. “Because most of these studies are observational rather than randomized trials, decisions to drink coffee and the amounts regularly consumed are likely associated with other variables that may confound observed associations.”

To help fill the gap, investigators conducted a prospective cohort study using mendelian randomization to evaluate the association between genetic polymorphisms that impact caffeine metabolism and arrhythmia. Researchers also assessed self-reported coffee consumption among participants as a predictor of future arrhythmias.

Researchers analyzed longitudinal data from the community-based UK Biobank study between January 2006 and December 2018. A total of 386 258 participants (mean age, 56 years; 52.3% female) were included in the new analysis.

During a mean follow-up of 4.5 years, 16 979 participants developed an incident arrhythmia. After adjusting for demographic characteristics, comorbid conditions, and lifestyle habits, each additional cup of coffee consumed was associated with a 3% lower risk of incident arrhythmia (hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.96-0.98; P<.001), according to the study.

When analyzing each arrhythmia alone, small reductions were observed for atrial fibrillation (HR, 0.97; 95% CI, 0.96-0.98; P<.001) and supraventricular tachycardia (HR, 0.96; 95% CI, 0.94-0.99; P=.002).

The mendelian randomization analyses did not provide evidence that coffee consumption increased the risk of arrhythmia, concluded researchers.

Study limitations included self-reported caffeine intake and that detailed information on the type of coffee (eg, espresso) or other caffeinated products was unavailable, wrote authors.

“Only a randomized clinical trial can definitively demonstrate clear effects of coffee or caffeine consumption,” said Marcus in a press release. “But our study found no evidence that consuming caffeinated beverages increased the risk of arrhythmia. Coffee’s antioxidant and anti-inflammatory properties may play a role, and some properties of caffeine could be protective against some arrhythmias.”