Lowered Risk of Irregular Heart Beat in Older Adults with Higher Blood Levels of DHA Omega-3
Jason, H. Y. et al., Circulation, 125: 1084-1093, 2012
Dept. of Epidemiology, Harvard School of Public Health, Boston, MA, USA
Atrial Fibrillation (AF) is the most common cardiac arrhythmia (irregular heart beat) in adults with the risk of AF increasing as one ages. AF increases various morbidities including the risk of stroke and death. Using various animal models, investigators have reported a preventive influence of fish oils containing DHA plus EPA on arrhythmias and several physiological and cellular mechanisms for such effects have been studied. In the present study, the investigators assessed whether the omega-3 status in the body as measured may bear a relationship to the onset of AF in the general population. For this investigation, men and women (3,326 in total) ages 65 years and over (free of AF or heart failure at initiation) had blood samples taken and their omega-3 status determined based on the levels of the long-chain omega-3 fatty acids (EPA/DPA/DHA) in the blood biomarker (plasma phospholipid). The subjects were followed for 10 years thereafter (including regular interim contact by telephone) and cases of AF were confirmed by ECG and other medical records.
During follow-up, 789 cases of AF were identified. Statistical analyses revealed an inverse relationship between higher circulating levels of the summed long-chain omega-3 fatty acids (as EPA plus DPA plus DHA) and the risk of AF. Those in the sector with the highest blood levels (top 25 %) showed a 29 % lower risk as compared to those in the bottom 25 % (based on blood levels) when adjusting for confounding factors. No significant relationship (statistically) between blood levels of EPA (eicosapentaenoic acid) or DPA (docosapentaenoic acid) and the risk of AF was found. However, a highly significant inverse relationship was observed in the case of DHA (docosahexaenoic acid) with those in the sector with the highest blood levels (top 25 %) having a 23 % lower risk than those in the bottom 25 % (based on blood levels). The authors conclude by suggesting that these omega-3 fatty acids could be beneficial for the prevention of the onset of AF in older subjects since they are a group at particular high risk.
Dr. Holub's Comments:
It is noteworthy that those subjects in the sector with the highest blood levels of DHA (in the phospholipid biomarker) had mean DHA levels at 4.37 % of total fatty acids. This study did not address the amount of dietary DHA/day which would be needed to attain such levels. However, previous published work from our group (Conquer and Holub , J. Lipid Res., 39: 286-292 (1998) found that daily intakes of 750 mg DHA/day and 1500 mg DHA/day gave DHA levels (in the phospholipid biomarker) at a mean of 6.4 % and 7.9 % of total fatty acids, respectively. It is also noted that average DHA intakes in the US are approximately 80 mg/day but approach 600 to 800 mg/day for a considerable portion of the Japanese population over the age of 50 years.