Positive Health Online

Abstract

MOZAFFARIAN and COLLEAGUES, Division of Cardiovascular Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Mass, USA. dmozaffa@hsph.harvard.edu analyzed whether consumption of fish is associated with heart rate variability, and improved risk of cardiac death.

Background

Fish and omega-3 fatty acid consumption reduce risk of cardiac death, but mechanisms are not well established. Heart rate variability (HRV) predicts cardiac death and reflects specific electrophysiological pathways and influences. The authors hypothesized that habitual consumption of fish and marine omega-3 fatty acids would be associated with more favourable HRV, citing electrophysiological influences and supporting effects on clinical risk.

Methodology

In a population-based cohort of older US adults, the authors evaluated cross-sectional associations of usual dietary fish and omega-3 consumption during the prior year and ECG-derived (n=4263) and 24-hour Holter monitor-derived (n=1152) HRV.

Results

After multivariable adjustment, consumption of tuna or other broiled/baked fish was associated with specific HRV components, including indices suggesting greater vagal predominance and moderated baroreceptor responses (eg, higher root mean square successive differences of normal-to-normal intervals [P=0.001]; higher normalized high-frequency power [P=0.008]; and lower low-frequency/high-frequency ratio [P=0.03]) and less erratic sinoatrial node firing (eg, lower Poincare ratio [P=0.02] and higher short-term fractal scaling exponent [P=0.005]) but not measures of circadian fluctuations (eg, 24-hour standard deviation of normal-to-normal intervals). Findings were similar for estimated dietary consumption of marine omega-3 fatty acids. For magnitudes of observed differences in HRV comparing the highest to lowest category of fish intake, differences in relative risk of cardiac death during 10.8 years of follow-up ranged from 1.1% (for difference in standard deviation of normal-to-normal intervals) to 5.9% and 8.4% (for differences in Poincare ratio and short-term fractal scaling exponent) lower risk.

Conclusion

Habitual tuna/other fish and marine omega-3 consumption are associated with specific HRV components in older adults, particularly indices of vagal activity, baroreceptor responses, and sinoatrial node function. Cellular mechanisms and implications for clinical risk deserve further investigation.

References

Mozaffarian D, Stein PK, Prineas RJ and  Siscovick DS. Dietary fish and omega-3 fatty acid consumption and heart rate variability in US adults.[see comment]. Circulation. 117(9):1130-7. Mar 4 2008.  Comment in: Circulation 19: 118(8): e129;  author reply e130; PMID: 18711019. Aug 2008.