That extra morning espresso, chai tea, or plain old cup of joe may give you a buzz, but it probably will not make your heart take extra beats, according to findings from a study examining the impact of food and drink consumption on cardiac ectopy.
Based on data gathered in community-dwelling participants in the Cardiovascular Health Study, there was no evidence that frequent consumption of caffeine-containing foods, including coffee, tea, or chocolate, had any impact on premature atrial contractions (PACs) and premature ventricular contractions (PVCs), reported Shalini Dixit, BA, of the University of California San Francisco, and colleagues.
After adjusting for potential confounders, more frequent consumption of these foods was not associated with ectopy, they wrote in the Journal of the American Heart Association.
"We found no evidence of a relationship between chronic caffeine consumption and frequency of these extra beats," co-author Gregory Marcus, MD, told MedPage Today. However, he added that the group was not able to measure the effects of acute caffeine exposure on heart rhythm, which was a study limitation.
In an accompanying editorial, cardiologists from the Atlanta VA Medical Center and Emory University reviewed the evidence examining the impact of caffeine consumption on the heart.
"Recently published studies, including prospective cohorts, clinical investigations, and meta-analyses, generally show coffee consumption is safe for the heart," wrote Peter W.F. Wilson, MD, and Heather Bloom, MD. "Concerning cardiovascular risk factors, there is little evidence that chronic coffee intake consumption raises blood pressure."
"Boiled coffee brewing may raise atherogenic lipid levels and other brewing methods do not appear to have this effect. Finally, there is little risk for atrial or ventricular arrhythmias at most of the levels of caffeine consumption in our society," they added.
The study by Dixit's group included 1,388 people over the age of 64 (46% male, mean age 72) without persistent atrial fibrillation (AF) who completed baseline food frequency assessments and underwent 24-hour ambulatory electrocardiography (Holter) monitoring.
A total of 840 (61%) participants reported consuming more than one caffeinated product per day. Women were more likely than men to consume at least one caffeine-containing product daily, and alcohol drinkers also consumed more caffeine than nondrinkers.
The authors reported that there were no differences in the number of PACs or PVCs/hour across levels of coffee, tea, and chocolate consumption. After adjustment for potential confounders, more frequent consumption of these products was not associated with ectopy.
Also, when combined dietary intake of coffee, tea, and chocolate were examined as a continuous measure, no relationships were observed after multivariable adjustment: 0.48% fewer PACs/hour (95% CI 4.60 to 3.64) and 2.87% fewer PVCs/hour (95% CI 8.18 to 2.43) per one-serving/week increase in consumption.
While premature cardiac contractions are common and often asymptomatic, there is increasing clinical evidence linking both PACs and PVCs to increased cardiovascular risk, the authors pointed out.
"Increased PACs, even among healthy individuals, have been associated with incident AF, stroke and death. Furthermore, the presence of PVCs in those free of heart disease has been associated with an increased risk of incident heart failure, CAD events and CAD-related deaths," they wrote.
They also noted that while caffeine consumption, especially coffee drinking, has long been related to cardiac ectopy and arrhythmias "by anecdote and biological plausibility," the evidence supporting the link is minimal.
Other study limitations included the reliance on participant self-report and the use of food frequency questionnaires, which assessed habitual dietary patterns over extended periods of time, rather than what the person consumed immediately before and during the Holter monitoring.
"This is really an interesting paradox," Marcus said. "The general belief is that caffeine is bad for your heart, but for most people this doesn't seem to be true. For people without arrhythmias, the data are pretty compelling that chronic consumption of caffeine does not lead to extra beats."
He added that there is even a reason to believe that caffeine may reduce the risk for atrial fibrillation.
"We found some evidence that caffeine may reduce some arrhythmias in our cohort," he said.
Despite the lack of supporting evidence, Marcus noted that clinicians and treatment guidelines often recommend either limiting caffeine consumption or complete avoidance to patients with premature cardiac contractions and arrhythmias.
"My clinical take is that the response to caffeine is somewhat idiosyncratic," he said. "It may trigger this response in some people, but not in others. So it is probably reasonable to allow patients who want to drink coffee or tea or eat chocolate to experiment to see how these products affect them."
Wilson and Bloom stated hat results from the current study are "relevant to healthy older adults who are relatively asymptomatic and who report modest amounts of caffeine intake."
They pointed out that the "epidemiology" of caffeine consumption has changed over the last 20 years, with the growing popularity of specialty coffee drinks and energy drinks.
"A restaurant double espresso (2 ounces, 150 mg caffeine, 0 calories) habit may not be problematic," but what, they asked, about a 20-oz peppermint mocha that clocks in at 415 mg caffeine and 440 calories or a 16-oz energy drink with 160 mg caffeine and 300 calories?
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