Effect of n-3 fatty acids on heart rate variability and baroreflex sensitivity in middle-aged subjects

Background N-3 fatty acids may reduce the risk of sudden death by preventing life-threatening cardiac arrhythmias. Heart rate variability (HRV) and baroreflex sensitivity (BRS) reflect cardiac autonomic regulation; reduced values predict arrhythmic events and mortality. Effects of n-3 fatty acids on these risk indicators of arrhythmia have not been widely studied. We investigated the effect of supplemental intake of n-3 fatty acids on HRV and BRS in apparently healthy subjects aged 50 to 70 years. Methods After a run-in period of 4 weeks, 84 subjects were randomized to receive capsules with either 3.5 g of fish oil or placebo oil daily for 12 weeks. Before and after intervention, electrocardiograms and blood pressure were recorded for 10 minutes with standardized respiration of 15 breaths/min. The SD of the duration of all normal RR intervals (SDNN10) and the root mean square successive differences (RMSSD10) were calculated from the 10-minute recordings. We also computed low frequency power (LF) and high frequency power (HF). BRS was computed by integrating the spectral systolic blood pressure to interbeat-interval transfer function in the 0.05- to 0.15-Hz bond. Results The different measures of HRV and BRS did not significantly improve with the intake of n-3 fatty acids. SDNN10 decreased by 3.05 ms or 7.7% (95% Q -8.91-2.82 ms), and BRS decreased by 0.92 ms/mm Hg or 0.1% (95% Cl, -2.66-0.81 ms/mm Hg) in the fish oil group compared with the placebo group. Conclusions N-3 fatty acids have no effect on HRV from short-term recordings and BRS in apparently healthy subjects.