High long-chain n-3 fatty acid intake attenuates the effect of high resting heart rate on cardiovascular mortality risk: A 24-year follow-up of Japanese general population

Background: Increased resting heart rate (RHR) independently predicts cardiovascular mortality. Meanwhile, long-chain n-3 fatty acids (LCn3FAs) have a cardioprotective effect. Our aim was to evaluate whether higher LCn3FAs intake attenuates the elevated risk of cardiovascular mortality associated with increased RHR. Methods: We conducted a population-based 24-year prospective cohort study of Japanese, whose LCn3FAs intake is relatively high. Study participants included 8807 individuals aged 30-95 years from randomly selected areas across Japan without cardiovascular diseases and anti-hypertensive drugs at baseline. The primary endpoint was cardiovascular mortality, and the secondary endpoints were cardiac and stroke mortality during 24 years of follow-up. Individual dietary LCn3FAs intake was estimated from household-based 3-day weighed food records. RHR was obtained from 3 consecutive R-wave intervals on 12-lead electrocardiography. Cox models were used to estimate the multivariable hazard ratios (HRs) and 95% confidence intervals (95% CIs) adjusting for possible confounders. Results: During the follow-up period, 617 cardiovascular deaths were observed. The median daily intake of LCn3FAs was 0.37% kcal (0.86 g/day). The interaction between dietary LCn3FAs intake and RHR in the risk of cardiovascular mortality was statistically significant (p = 0.033). The risk of cardiovascular mortality was significantly higher in the low-intake group (<0.37% kcal) with an RHR >85 beats/min (bpm) [hazard ratio (HR), 1.67; 95% confidence interval (CI), 1.15-2.43], but not in the high-intake group (>= 0.37% kcal) with an RHR >85 bpm (HR, 0.92; 95% CI, 0.61-1.38), compared with those in the high-intake group with an RHR <70 bpm. Similar results were observed with stroke mortality, but not with cardiac mortality. Conclusions: The risk of cardiovascular mortality associated with increased RHR is elevated in participants with low dietary LCn3FAs intake, but not in participants with high dietary LCn3FAs intake in a representative Japanese general population. These results suggest that high dietary LCn3FAs intake may prevent cardiovascular mortality associated with increased RHR. (C) 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.