Taking high-doses of marine omega-3 fatty acids, more than 1 gram daily, may raise the risk for atrial fibrillation (AFib), according to a meta-analysis of relevant research.
Dr. Christine M. Albert
However, the risk of developing AFib appears to be “relatively small” for those taking 1 gram or less of fish oil per day, Christine M. Albert, MD, chair of the department of cardiology at the Smidt Heart Institute at Cedars-Sinai, Los Angeles, told this news organization.
The study was published online Oct. 6 in the journal Circulation.
It’s estimated that 7.8% of U.S. adults – almost 19 million in all – take fish oil supplements, often unbeknownst to their health care providers, the researchers noted. Yet, the literature on the effects of omega-3 fatty acid supplementation on cardiovascular outcomes are mixed.
“Some, but not all” large-scale randomized controlled trials investigating the effects of marine omega-3 fatty acid supplements on cardiovascular outcomes have reported increased risks for AFib. The potential reasons for differing findings may be dose related, the authors note in their paper.
The goal of this meta-analysis was to “bring clarity, answers, and actionable information” to doctors and patients, said Dr. Albert. The results suggest, however, that there may not be a “straightforward answer” to whether fish oil is good or bad for AFib. Instead, the answer may depend on the dose, she added.
Pooled data
After screening 4,049 articles and abstracts, the researchers included in their analysis seven large-scale randomized controlled trials reporting cardiovascular outcomes of marine omega-3 fatty acids.
The trials reported results for AFib, either as prespecified outcome, adverse event, or a reason for hospitalization. Each had a minimum of 500 patients and a median follow-up of at least 1 year.
Trials examining the effects of omega-3 fatty acids on recurrent AFib in patients with established AFib or postoperative AFib were excluded.
The seven trials enrolled a total of 81,210 patients (mean age, 65 years; 39% women); 72.6% of participants were enrolled in clinical trials testing ≤1 gram of marine omega-3 fatty acids per day and 27.4% were enrolled in clinical trials testing >1 gram of the supplement per day. The weighted average follow-up was 4.9 years.
Overall, use of omega-3 fatty acids was associated with a 25% increased risk for AFib (hazard ratio, 1.25; 95% confidence interval, 1.07-1.46; P = .013).
In analyses stratified by dose, the risk for AFib was “significantly more pronounced” in trials testing high doses of marine omega-3 fatty acid supplements (>1 gram per day: HR, 1.49; 95% CI, 1.04-2.15; P = .042) compared with those testing lower doses (≤1 gram per day: HR, 1.12; 95% CI, 1.03-1.22; P = .024; P for interaction < .001).
In meta-regression, the HR for AFib increased per 1 gram increase in daily omega-3 fatty acid dose (HR. 1.11; 95% CI, 1.06-1.15; P = .001).
Risk-benefit balance
“This meta-analysis adds new evidence regarding the risk of AFib in patients taking marine omega-3 fatty acid supplements,” wrote Dr. Albert and colleagues.
“Since the benefit of omega-3 fatty acids also appears to be dose dependent, the associated risk of AFib should be balanced against the benefit on atherosclerotic cardiovascular outcomes,” they suggested.
They cautioned that the meta-analysis pooled aggregate-level trial data, not individual patient data. Therefore, subgroup analyses by age or other patient level characteristics were not possible.
The risk of developing AFib increases with advancing age and is more common in men than in women. Additional risk factors include elevated blood pressure, coronary artery disease, heart failure, heart valve defects, obesity, and diabetes.
The authors said the potential risk of developing AFib with high doses of omega-3 fatty acid supplements should be discussed with patients and they should know the signs and symptoms of the condition.
The study had no specific funding. Dr. Albert has received grants from St. Jude Medical, Abbott, and Roche Diagnostics.
A version of this article first appeared on Medscape.com.