38 trials included
For the current paper, Dr. Bhatt and coauthors performed a comprehensive literature search for randomized trials comparing omega-3 fatty acids with control (placebo, no supplementation, or lower dose of omega-3 fatty acids) in adults, with a follow-up of at least 12 months, and mortality and cardiovascular outcomes as endpoints.
Ultimately, 38 trials encompassing 149,051 patients were included. Of these, four trials compared EPA with control, 34 trials compared EPA+DHA with control, and 22 trials were in primary prevention. The dose of omega-3 fatty acids ranged from 0.4 g/day to 5.5 g/day.
A total of 25 trials with 143,514 individuals reported 5,550 events of cardiovascular mortality, and 24 trials with 140,983 individuals reported 10,795 events of all-cause mortality.
Omega-3 fatty acids were associated with reduced cardiovascular mortality (rate ratio, 0.93; P = .01), but not all-cause mortality (RR, 0.97; P = .27). The meta-analysis showed reduction in cardiovascular mortality with EPA monotherapy (RR, 0.82; P = .04) and EPA+DHA combination (RR, 0.94; P = .02).
A total of 20 trials with 125,611 individuals reported 2,989 nonfatal myocardial infarction events, and 29 trials with 144,384 individuals reported 9,153 coronary heart disease (CHD) events.
Omega-3 fatty acids were associated with reducing nonfatal MI (RR, 0.87; P = .0001) and CHD (RR, 0.91; P = .0002). The meta-analysis showed higher risk reductions in nonfatal MI with EPA monotherapy (RR, 0.72; P = .00002) than with EPA+DHA combination (RR, 0.92; P = .05), and also for CHD events with EPA monotherapy (RR, 0.73; P = .00004) than with EPA+DHA combination (RR, 0.94; P = .01).
A total of 17 trials (n = 135,019) reported 13,234 events of MACE, and 13 trials (n = 117,890) reported 7,416 events of revascularization.
Omega-3 fatty acids were associated with reducing MACE (RR, 0.95; P = .002) and revascularization (RR, 0.91; P = .0001). The meta-analysis showed higher risk reductions in MACE with EPA monotherapy (RR, 0.78; P = .00000001), whereas EPA+DHA combination did not reduce MACE (RR, 0.99; P = .48). This effect was consistent for revascularization.
A total of eight trials with 65,404 individuals reported 935 nonfatal strokes, and eight trials with 51,336 individuals reported 1,572 events of atrial fibrillation (AFib).
Omega-3 fatty acids did not significantly reduce nonfatal stroke (RR, 1.04; P = .55), but EPA monotherapy was associated with a reduction of nonfatal stroke, compared with control (RR: 0.71; P = .01).
Conversely, omega-3 fatty acids were associated with increased risk for AFib (RR, 1.26; P = .004), with a higher risk with EPA monotherapy than with control (RR, 1.35; P = .004).
Overall, omega-3 fatty acids did not prevent sudden cardiac death or increase gastrointestinal-related adverse events, total bleeding, or major or minor bleeding; however, the meta-analysis showed a higher risk of total bleeding with EPA monotherapy than with control (RR, 1.49; P = .006).
An influence analysis with stepwise exclusion of one trial at a time, including REDUCE-IT, did not alter the overall summary estimates. “Despite the exclusion of REDUCE-IT, EPA monotherapy reduced MACE by 23%, compared with the control,” the authors reported.
They said these new findings also have important implications for clinical practice and treatment guidelines.
“After REDUCE-IT, several national and international guidelines endorsed EPA in their therapeutic recommendations. However, the publication of two recent negative trials of EPA + DHA has created some confusion in the scientific community about the value of omega-3 FAs in preventing atherosclerotic cardiovascular disease [ASCVD],” they stated.
“This meta-analysis provides reassurance about the role of omega-3 fatty acids, specifically EPA, in the current treatment framework of ASCVD residual cardiovascular risk reduction and encourages investigators to explore further the cardiovascular effects of EPA across different clinical settings,” they added.
REDUCE-IT was sponsored by Amarin. Brigham and Women’s Hospital receives research funding from Amarin for the work Dr. Bhatt did as the trial chair and as the international principal investigator. The present analysis was unfunded.
A version of this article first appeared on Medscape.com.