Eat More Chocolate, Have Less Atrial Fibrillation? Hope Springs Eternal

Liam Davenport

May 31, 2017

COPENHAGEN, DENMARK — People who regularly consume moderate amounts of chocolate also seem to have a reduced risk for developing atrial fibrillation (AF), according to an analysis, which is being interpreted cautiously, based on a large, prospective cohort study from Denmark[1].

Lots of published studies have suggested that regular consumption of chocolate, especially dark chocolate, is associated with heart and vascular benefits that include lower rates of cardiovascular events, stroke, and heart failure, possibly due to the confection's large flavonoid content. But the current analysis is unusual for associating chocolate with less incident AF.

According to the analysis of 55,502 persons in the Danish Diet, Cancer, and Health Study, which enrolled people aged 50 to 64 years between December 1993 and May 1997, consuming chocolate one to three times a month was associated with a 10% risk of incident AF compared with partaking of the treat less than once a month.

But in the study published May 23, 2017 in Heart, the "benefit" appeared to plateau and was only marginally greater with more frequent chocolate consumption. That would be expected because "there's only so much benefit one can expect," lead author Dr Elizabeth Mostofsky (Harvard School of Public Health, Boston, MA) told heartwire from Medscape.

And, she said, "Because chocolate entails also a lot of sugar and fat, it's only beneficial in moderation." Nevertheless, "there's so little known about ways to prevent arrhythmia and it's such a huge public-health burden that any lifestyle factors that we think could be associated with prevention seem to be of interest."

Message Would Resonate With the Public

In an accompanying editorial[2], Drs Sean D Pokorney and Jonathan P Piccini (Duke University Medical Center, Durham, NC) agreed that it is "exciting" to imagine public-health announcements encouraging chocolate consumption, as they "would resonate well, and patients might be more than happy to comply with this healthcare advice."

But the pair wondered whether the idea is "too good to be true," noting a number of limitations to the study, including that the chocolate consumers were generally healthier and better educated than other participants and that it is not possible to determine whether the incidence of all or only clinically apparent AF is associated with chocolate consumption.

Regardless, Pokorney and Piccini say that the findings are "interesting and warrant further consideration, especially given the importance of identifying effective prevention strategies for AF."

At baseline in the study, participants completed a 192-item food frequency questionnaire that was validated against two 7-day weight diet records. Each participant was also matched to the Danish National Patient Register to gather data on incident clinically apparent AF or atrial flutter.

Defining a serving of chocolate as about 1 oz, or 30 g, the team found that 12,258 of the >55,000 participants reported consuming chocolate less than once a month, while 22,909 had an intake of one to three servings per month, 10,620 ate one serving per week, 8476 ate two to six servings per week, and 1239 one or more servings per day.

The questionnaire used did not distinguish between milk or dark chocolate, but, as the team notes, in Denmark most of the chocolate consumed is milk chocolate.

Over mean follow-up of 13.5 years, there were 3346 incident cases of AF. In multivariate analysis, the rate of AF was lower for those consuming one to three servings per month, at a hazard ratio of 0.90 (95% CI 0.82–0.98) compared with a chocolate intake of less than one serving per month.

The impact of increased chocolate consumption on the risk of AF subsequently leveled off at an HR 0.83 (95% CI 0.74–0.92) for one serving per week, 0.80 (95% CI 0.71–0.91) for two to six servings per week, and 0.84 (95% CI 0.65 to 1.09) for one or more servings/day P-linear trend<0.0001).

Effect Seen in Both Women and Men

Although incident AF was less common among women than men, the relationship between increased chocolate and a reduced AF incidence remained significant for both men (P for trend=0.002) and women (P for trend=0.017) after researchers took potential confounding factors into account.

Further analysis indicated that the findings were confounded by history of hypertension and cardiovascular disease or by adjustment for caffeine intake and coffee consumption.

The editorialists Pokorney and Piccini pointed to the ongoing Cocoa Supplement and Multivitamin Outcomes Study (COSMOS), a randomized trial looking at whether daily supplements of cocoa extract and/or a standard multivitamin reduces the risk of developing cardiovascular disease and cancer. However, the end points don't include AF.

"The highest-quality care for AF is to prevent it in the first place. It will be interesting to see if chocolate is an effective preventive therapy," they write.

This work was conducted with support from grants from the National Heart, Lung, and Blood Institute, the European Research Council, EU 7th Research Framework Program, a KL2/Catalyst Medical Research Investigator Training award from Harvard Catalyst, the Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health Award), and the Danish Cancer Society and the Danish Council for Strategic Research (Aalborg AF-Study Group). The authors report no relevant financial relationships. Pokorney reports modest consulting support from Boston Scientific and Medtronic; modest research support from Gilead, Boston Scientific, Bristol-Myers Squibb, Pfizer, and Janssen Pharmaceuticals. Piccini reports grants for clinical research from ARCA biopharma, Boston Scientific, Gilead, St Jude Medical, and Spectranetics and serving as a consultant to Allergan, Amgen, GlaxoSmithKline, Medtronic. and Spectranetics.

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