A randomized clinical trial of omega-3 fatty acid and vitamin D supplementation on electrocardiographic risk profiles

Associations Between Plasma Omega-3, Fish Oil Use and Risk of AF in the UK Biobank

Objective

To determine the relationship between plasma omega-3 levels and incident atrial fibrillation (AF), and the association between fish oil supplement (FOS) use and risk for AF.

Methods and Analysis

Recent studies in UK Biobank concluded that FOS use was associated with increased risk of incident AF. Conversely, a meta-analysis found inverse relationships between blood levels of omega-3 and AF risk. We performed a prospective observational study linking plasma omega-3 levels and reported FOS use with AF risk in UK Biobank. Among UK Biobank participants without prevalent AF, 261 108 had plasma omega-3 levels and 466 169 reported FOS use. The primary outcome was incident AF during follow-up (median 12.7 years). Multivariable-adjusted hazard ratios (HR, 95% confidence intervals, CI) for fatty acids were computed continuously (per inter-quintile range, IQ5R) and by quintile. Hazard ratios were computed for dichotomous fish oil supplement use.

Results

Plasma omega-3 levels were inversely associated with incident AF (HR per IQ5R = 0.90, 95% CI 0.86, 0.93; HR=0.87 [0.83, 0.91] in quintile 5 vs quintile 1). Fish oil supplement use was reported by 31% of the cohort and was more common in older individuals. After adjusting for age as a continuous variable, no association was observed between fish oil supplement use and AF risk (HR=1.00; 95% CI 0.97, 1.02).

Conclusion

Higher circulating omega-3 levels were linked to reduced AF risk in UK Biobank. Further, after age was adjusted for as a continuous variable, no association was found between fish oil supplement use and AF.

Unraveling the discrepancies between REDUCE-IT and STRENGTH trials with omega-3 fatty acids: new analytical approaches

Two large-scale, randomized, double-blind, placebo-controlled trials-REDUCE-IT and STRENGTH-have garnered significant attention in cardiovascular medicine. Both trials aimed to evaluate the effects of prolonged administration of nutritional lipids, specifically omega-3 fatty acids, on major adverse cardiovascular events (MACEs) in high-risk patients undergoing statin therapy. REDUCE-IT used eicosapentaenoic acid (EPA) ethyl ester with mineral oil as a control, while STRENGTH utilized a carboxylic acid formulation of both EPA and docosahexaenoic acid (DHA) with corn oil as a control. Notably, REDUCE-IT demonstrated a reduction in MACE risk with EPA, whereas STRENGTH showed no such benefit with the combination of EPA and DHA. Despite extensive and insightful discussions following the publication of these trials, the underlying reasons for this discrepancy remain elusive. We posit that further investigation into resting heart rate (RHR), heart rate variability (HRV), and ethnic subgroup data-collected but not fully explored-is critical to unraveling the divergent outcomes of the REDUCE-IT and STRENGTH trials. These additional analyses could provide pivotal insights into the mechanisms driving the differential effects of omega-3 fatty acids in high-risk cardiovascular patients. Given that previous discussions have not fully addressed these potential variables, exploring them may illuminate unexplored pathways and offer a deeper understanding of the mechanistic and clinical roles of omega-3 s in cardiovascular health. We hypothesize that by delving into these under-analyzed factors, we can not only clarify the discrepancies between the trials but also advance our broader understanding of cardiovascular nutrition and medicine.

Omega-3 and Risk of atrial fibrillation: Vagally-mediated double-edged sword

OBJECTIVE

Studies regarding effects of omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on risk of atrial fibrillation (AF) have reported discordant results. The aim of this review is to clarify effects of marine omega-3 intake on risk of AF.

PATIENTS AND METHODS

A PubMed search was performed using terms: atrial fibrillation, omega-3, EPA, DHA, vagal tone. We summarized findings from randomized clinical trials (RCTs), epidemiology studies, and meta-analyses evaluating effects/associations of DHA + EPA on risk of AF. Also, vagal tone was explored as a mediator between omega-3 and risk of AF.

RESULTS

Meta-analyses of 8 RCTs and 17 prospective cohort studies comprised of 83,112 and 54,799 individuals, respectively, investigated the link between omega-3 intake and incident AF. The RCTs reported that treatment with DHA and/or EPA was associated with a 24 % increased relative risk of AF (absolute risk 4.0 % vs 3.3 %; relative risk [RR] 1.24, 95 % confidence interval [CI] 1.11-1.38, p = 0.0002). This was dose-dependent; DHA + EPA doses of ∼1000 mg/d increased AF risk ∼12 %, whereas 1800 to 4000 mg/d increased AF risk by ∼50 %. In contrast, observational studies focused on DHA + EPA blood levels or dietary intake have generally reported that higher omega-3 levels/consumption are associated with lower AF risk. Maximal AF risk reduction. (12 %) occurred at ∼650 mg/d of dietary DHA + EPA. Other studies have indicated that omega-3 fatty acids can dose-dependently increase vagal tone, which could explain the biphasic relationship between DHA + EPA and AF risk. Experimental studies show that low-level vagal stimulation decreases risk of AF, whereas high-level vagal stimulation increases risk of AF.

CONCLUSION

Higher consumption of dietary omega-3 is associated with decreased AF risk. In contrast, pharmaceutical dosing of omega-3 increases AF in a dose-dependent manner, which may be mediated by vagal tone.