Cohorts, Meta-Analysis: No Link Between Coffee and Increased Risk for Atrial Fibrillation

Deborah Brauser

September 23, 2015

STOCKHOLM, SWEDEN ( updated with commentary ) — More research is weighing in with a resounding "no" on whether downing coffee may be detrimental to cardiovascular health in otherwise-healthy adults.

Analysis of more than 76,000 participants in the prospective Cohort of Swedish Men and Swedish Mammography Cohort showed that, although there were more than 7000 cases of atrial fibrillation (AF), there was no association with coffee consumption[1].

A complementary meta-analysis of six studies, which included almost 250,000 total participants, showed an overall relative risk (RR) for AF of 0.96 (95% CI 0.84–1.08) for the participants who drank the most coffee vs those who drank the least amounts and an RR of 0.99 (95% CI 0.94–1.03) for every two cups of coffee consumed per day.

Lead author Dr Susanna C Larsson (Karolina Institutet, Stockholm, Sweden) told heartwire from Medscape via email that the results were not very surprising. "The take-home message is that coffee lovers can continue to drink coffee, at least in moderation, without the risk of developing atrial fibrillation," said Larsson.

However, she noted that the study could not answer whether coffee consumption may trigger arrhythmia in patients who already have AF.

The findings were published online September 23, 2015 in BMC Medicine.

Cardioprotective?

As reported by heartwire , past research has shown that coffee consumed in moderation may protect against heart failure. In a recent meta-analysis from Chinese researchers, there was no association between caffeine consumption and increased AF risk. In fact, the investigators found that habitual consumption of caffeine may reduce the risk.

Larsson noted that because there has been past speculation that high consumption of coffee, specifically, could increase risk of AF, her team wanted to investigate the possible association.

They evaluated 41,881 men and 34,594 women from the two Swedish cohorts who provided data on their coffee consumption in diet and lifestyle questionnaires mailed out in 1997. After 12 years of follow-up, there were 4311 cases of incident AF in the men and 2730 cases in the women, as ascertained by linkage to the Swedish Hospital Discharge Register.

The mean daily coffee consumption for the entire group was three cups. There were no significant associations between coffee consumption and increased risk of AF, even after researchers removed those with prior cardiac disease or hypertension and those who didn't drink any coffee.

No Significant Associations

The meta-analysis included both of the Swedish registries as well as four other "coffee-and-AF" studies, including two conducted in the US, for a total of 248,910 participants. There were 10,406 cases of diagnosed AF.

Five of the six studies showed no significant association between coffee consumption and AF. The remaining study[2] actually showed that those who drank the highest amount of coffee had a significantly reduced risk of AF vs those who drank the lowest amount. However, no dose-response relationship was found.

In combined study analysis, the RR for AF was 0.96 for the highest vs lowest coffee consumption and was 0.93 after exclusion of the one study that didn't adjust for smoking status (95% CI 0.80–1.08).

Stratified analyses showed RRs for AF were:

  • 0.89 (95% CI 0.71–1.12) for the two US studies,

  • 0.99 (95% CI 0.86–1.15) for the four Swedish studies,

  • 1.08 (95% CI 0.99–1.19) for men.

  • 0.91 (95% CI 0.80–1.04) for women.

However, the investigators note that because the included studies were from just two countries, the generalizability of the findings may be reduced.

In addition, Larsson noted that the individuals who were excluded for having AF at baseline consumed less coffee than those without the condition. "This may suggest that coffee might trigger arrhythmia in [these] patients," she said, adding that a previous study of 100 patients with AF did, indeed, suggest that coffee was a triggering factor.

Still, in the study population without AF, risk for developing AF was not associated with coffee consumption, write the investigators; but they note that larger prospective studies are needed.

Punitive Restrictions?

"This observational, epidemiology study looks well done," Dr Stanley Nattel (University of Montreal, QC) told heartwire .

Nattel, who was not involved with this research, pointed out that the Chinese meta-analysis published last year also found no link between caffeine consumption and AF.

"I think a picture is coming out pretty consistently that, in general, coffee consumption doesn't seem to increase AF risk. So it's not something that doctors need to tell these patients to avoid," he said.

However, he noted that it's important to be aware that in an epidemiology study such as this, the possibility isn't completely excluded that some individuals may have AF episodes triggered by coffee.

"But it could be that these people have AF triggered by anything, such as cold water or ice cream. In fact, there's probably more biological plausibility to cold drinks precipitating this or GI upset than there is to coffee," said Nattel.

"I put coffee in the category of 'punitive restrictions' that physicians sometimes force on patients without much evidence," he said. "Unless there's a strong reason to think that there's a relationship within a given patient, one has to be very careful about forbidding things that are important to an individual's lifestyle."

The study was funded by the Swedish Research Council and by a Young Scholars Award grant from the Strategic Research Area in Epidemiology at Karolinska Institutet. The study authors report no relevant financial relationships.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....