BOSTON, MASSACHUSETTS. In 2009 Finnish researchers reported that high levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) in the serum phospholipid phase were associated with a significant decrease in the risk of developing atrial fibrillation (AF). The study involved 2174 men aged 60 years or younger at baseline in 1984. During 18 years of follow-up, 11% of study participants were diagnosed with AF upon admission to hospital (for arrhythmia or other reasons). At baseline, the mean percentages of EPA, DPA and DHA in serum fatty acids were 1.67%, 0.55% and 2.46% respectively. After adjustment for age and other possible confounders the researchers observed that men in the highest quartile of EPA+DPA+DHA concentration (5.3 � 15.6%) had a 35% reduced risk of developing AF when compared to men in the lowest quartile (1.7 � 3.6%). The absolute risk in the lowest quartile group was 13.4% vs 8.7% in the highest quartile group. Further analysis revealed that DHA accounted for the entire risk reduction and that EPA and DPA levels were not associated with risk of developing AF.

Considering only lone afibbers (no heart disease prior to diagnosis of AF) strengthened the association between serum fatty acid concentration of DHA and AF risk. Men in the lowest quartile had a risk of 10.9%, while those in the highest quartile had a risk of only 5.6% � a relative risk reduction of 49%.

Now researchers from Harvard School of Health and a group of other research centers confirm that high phospholipid levels of EPA, DPA and EPA (the main components of fish oil) also help prevent the development of AF in older men and women. Their study involved 3326 American men and women aged 65 years or older at enrolment in the Cardiovascular Health Study in 1989 to 1990. None of the participants had AF or heart failure at baseline. Blood serum levels of EPA, DPA and DHA were measured at baseline as percentages of total phospholipid fatty acid concentration.

During 31,169 person-years of follow-up, 789 cases of AF were diagnosed either through hospital admission records or routine annual ECG readings. This corresponds to an incidence (new cases diagnosed) of 2.5%/year. A high percentage of EPA+DPA+DHA in the phospholipid phase (average 6.4%), after adjusting for potential confounders, was found to be associated with a 27% relative reduction in the risk of developing AF when compared to an average level of 2.9%. The risk reduction was almost entirely attributable to DHA which, on its own, was associated with a 23% relative risk reduction when comparing the highest quartile of phospholipid level (4.37%) to the lowest quartile (1.98%). In absolute terms, the risk of developing AF was 1.9%/year in the highest quartile group versus 2.8%/year in the lowest quartile group.

The researchers point out that long-chain n-3 polyunsaturated fatty acids (PUFAs) such as found in fish oil have several important biological effects on a range of cellular functions that may reduce the risk of developing AF. Among these are improvement in myocardial efficiency, and significant anti-inflammatory and anti-fibrotic effects that may reduce long-term atrial remodelling and limit the creation of an �AF-friendly� substrate. There is also evidence that PUFAs directly affect cardiac electrophysiology through modulation of ion channels, potentially increasing myocardial electric stability. The researchers recommend a randomized trial to test the efficacy of PUFAs (fish oil) for prevention of the development of AF in older adults.
Wu, JHY, et al. Association of plasma phospholipid long-chain omega-3 fatty acids with incident atrial fibrillation in older adults. Circulation, Vol. 125, March 6, 2012, pp. 1084-93

Editor�s comment: Fish oil has now been shown to have strong anti-inflammatory properties, and to help prevent the development of AF, help reduce ventricular ectopy (PVCs), help prevent AF recurrence following catheter ablation, help prevent atrial mechanical stunning (an important stroke risk) after cardioversion and catheter ablation, help prevent sudden cardiac death, and has many more beneficial effects. I see no need to wait for the results of another clinical trial before embarking on daily fish oil supplementation.