Physicians generally do not need to advise patients with atrial fibrillation to avoid moderate coffee consumption solely to reduce recurrence risk, according to an American Heart Association scientific statement published in Circulation.
The writing group concluded that habitual moderate coffee consumption could be part of a healthy lifestyle for most adults. However, the available evidence did not establish that coffee prevents cardiovascular disease or that patients who currently abstain should begin drinking it for cardiovascular benefit.
Most of the evidence concerned coffee rather than caffeine in isolation. Coffee contains multiple bioactive compounds, and favorable associations reported with both caffeinated and decaffeinated coffee suggested that caffeine may not be responsible for the observed outcomes.
The statement summarized prospective cohort studies, systematic reviews, meta-analyses, Mendelian randomization analyses, and randomized clinical trials examining blood pressure, type 2 diabetes, blood lipids, coronary artery disease, heart failure, stroke, atrial fibrillation, and other arrhythmias.
Moderate consumption—up to approximately 400 mg of caffeine daily, corresponding to roughly three to five 8-ounce cups of coffee—appeared safe for most adults. The statement noted that caffeine content varies by coffee type and serving size.
AF and PVC Findings Diverged
Observational studies generally found no higher risk of atrial fibrillation (AF) with moderate coffee consumption and, in some analyses, found a lower risk.
In the DECAF randomized clinical trial, patients with AF who had consumed caffeinated coffee during the preceding 5 years and were scheduled for elective cardioversion were assigned to drink at least one cup of caffeinated coffee daily or avoid coffee and caffeine. Daily coffee consumption reduced the risk of recurrent AF by 39% in this selected population.
The finding was consistent with a Class 3 recommendation in current atrial fibrillation guidelines advising clinicians not to recommend caffeine avoidance solely to reduce AF risk, although the guideline preceded the DECAF trial.
The effect did not extend uniformly to other rhythm abnormalities. In the CRAVE randomized case-crossover trial involving 100 ambulatory adults, caffeinated coffee increased premature ventricular contractions (PVCs) but did not increase premature atrial contractions, the trial’s primary rhythm outcome.
Case reports and small series have also described AF following energy-drink consumption among otherwise low-risk patients. Extremely high doses of caffeine, particularly in concentrated powder or capsule form, have been associated with ventricular fibrillation and sudden death in case reports.
Most Long-Term Evidence Was Observational
Across 30 prospective cohort studies, consumption of up to six cups of coffee daily was not associated with a higher risk of coronary artery disease. Light consumption, with a median of 1.5 cups daily, and moderate consumption, with a median of 3.5 cups daily, were each associated with an approximately 10% lower risk.
A dose-response meta-analysis of 20 cohort studies found a U-shaped association between coffee consumption and stroke. The lowest risk occurred at three to four cups daily, which was associated with a 21% lower risk compared with little or no consumption.
Heart failure studies also suggested a nonlinear association, with the lowest risk at approximately four cups daily. Those findings came from observational cohorts rather than randomized heart failure trials, however, and many studies were not designed primarily to evaluate caffeine exposure. The studies also often relied on administrative coding and could not distinguish between heart failure with reduced and preserved ejection fraction.
Habitual coffee consumption was consistently associated with a lower incidence of type 2 diabetes in observational studies. Similar associations with caffeinated and decaffeinated coffee suggested that noncaffeine compounds could contribute. Short-term clinical trials produced inconsistent glucose findings, and some suggested unfavorable acute effects.
Because most favorable findings came from observational research, residual confounding and healthy-user bias may have contributed to the reported associations.
Acute and Habitual Effects May Differ
The writing group emphasized that acute caffeine exposure can have different effects from habitual consumption. Acute intake can transiently increase blood pressure and blood glucose and may cause palpitations or disrupt sleep in susceptible patients.
The long-term relationship with blood pressure remained uncertain. Prospective studies suggested a nonlinear association between habitual coffee intake and hypertension, whereas high intake, severe hypertension, or heightened caffeine sensitivity could increase risk in some patients.
Coffee preparation was also relevant. Cafestol in unfiltered coffee increased low-density lipoprotein cholesterol in randomized trials. French press, Greek or Turkish, Scandinavian boiled, and some espresso-based coffees contain more cafestol than paper-filtered or instant coffee.
Added sugar, flavored syrups, and high-calorie dairy products may also counteract potential benefits associated with coffee itself.
“Potential health benefits that have been observed among individuals consuming caffeine that occurs in natural substances should not be extrapolated to synthetic products or high-dose caffeine. Indeed, although data on energy drinks are limited, available studies generally suggest cardiovascular harm,” wrote writing group chair Gregory M. Marcus, MD, of the University of California, San Francisco, and colleagues.
“Although data on energy drinks are limited, available studies generally suggest cardiovascular harm,” wrote writing group chair Gregory M. Marcus, MD, of the University of California, San Francisco, and colleagues.
Disclosures: Frank B. Hu, MD, reported a research grant from Analysis Group. Thomas A. Dewland, MD, reported consulting fees from Boston Scientific. Marilyn C. Cornelis, PhD, reported an unpaid role with the Institute for the Advancement of Food and Nutrition Sciences Caffeine Working Group. The other writing group members reported no disclosed relationships.
Source: Circulation
