Supplementing with cocoa flavanol may reduce atrial fibrillation over time

The central theses:

• Participants who took cocoa extract supplements experienced a significant reduction in cases of atrial fibrillation after 5.5 years.
• The properties of cocoa flavanols can lead to a remodeling of the atrium that protects against atrial fibrillation.

Cocoa flavanols may reduce the risk of atrial fibrillation over time, possibly as a result of atrial remodeling, according to a secondary analysis of a completed study published in. European Journal of Preventive Cardiology.

Although several large-scale, long-term cohort studies have examined the association between cocoa flavanols and cardiovascular health, researchers say information on the association between AF and cocoa flavanols is lacking.

This motivated Melissa E. Middeldorp, PhD, MPHPostdoctoral fellow in the Department of Cardiology at the University Medical Center Groningen (Netherlands), and colleagues were designed to conduct a secondary analysis of the COSMOS study to specifically examine atrial fibrillation as an outcome.

The original COSMOS study involved 21,422 American adults to find out whether taking 500 mg of flavanol supplements or a multivitamin could prevent cardiovascular disease and cancer. As Healio previously reported, results showed that participants randomly assigned to receive the cocoa flavanol supplement had a 27% lower risk of cardiovascular death than those who received a placebo.

Of all COSMO participants, 18,188 individuals who had no history of cardiac arrhythmia at baseline and completed a biannual questionnaire on new physician diagnoses of atrial fibrillation were included in the secondary analysis.

Middeldorp and colleagues found that during an average follow-up of 5.5 years, 1,029 participants (5.7%) reported a diagnosis of atrial fibrillation. Of these cases, 694 occurred during an average randomized treatment period of 3.5 years—including 333 in the cocoa extract group and 361 in the placebo group—and 335 during an average follow-up period of 2 years after the intervention, including 144 in the extract group and 191 in the placebo group.

Using Cox proportional hazard models, the results showed that atrial fibrillation during the intervention period did not differ significantly between the cocoa extract and placebo groups (HR = 0.92; 95% CI, 0.79–1.06; P = .24), a significant reduction was observed after 5.5 years of cumulative follow-up (HR = 0.85; 95% CI, 0.75-0.96; P = .01).

In addition, the researchers found that participants who took the cocoa extract supplement experienced a significant reduction in cases of atrial fibrillation in the post-intervention period compared with the placebo group (HR = 0.75; 95% CI, 0.6-0.93).

Limitations included that atrial fibrillation was not a pre-specified endpoint of the COSMOS trial and that the atrial fibrillation events that occurred were based on self-reporting and therefore the results could potentially be biased toward the null, the researchers wrote.

Middeldorp and his colleagues hypothesized that the vasodilatory, anti-inflammatory, antioxidant, antiplatelet and angiotensin-converting properties of cocoa flavanols may lead to an “electrical and structural remodeling of the atria, which may protect against the development of atrial fibrillation.” This would also explain why the reduction in the number of atrial fibrillation events was only visible after a longer follow-up of 5.5 years, by which time the remodeling of the atria may already have occurred.

“Based on these promising study results, it is appropriate to further investigate the hypothesis that cocoa flavanols may reduce the risk of atrial fibrillation in future randomized trials,” wrote Middeldorp and his colleague.

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Sources/Disclosures

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Disclosure: Middeldorp does not report any relevant financial disclosures. The relevant financial disclosures of all other authors can be found in the study.

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