Level 1: Likely reliable evidence
Evidence for the effect of omega-3 fatty acids on cardiovascular (CV) risk has been inconsistent. While some systematic reviews have found little or no evidence that dietary or supplementary omega-3 fatty acid intake alters the risk of death or CV events in primary or secondary prevention (Cochrane Database Syst Rev. 2004;4:CD003177; Arch Intern Med. 2012;172:686-694), others have shown some benefit against cardiac mortality (BMJ. 2008;337:a2931; Ann Med. 2009;41:301-310).
The recently reported ORIGIN trial examined the effects of supplementation in 12,611 patients with impaired fasting glucose, impaired glucose tolerance, or type 2 diabetes (N Engl J Med. 2012;367:309-318).
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Patients older than age 50 years (mean age 64 years, 88% with diabetes) were randomized to omega-3 fatty acids 1 g orally once daily (Omacor capsule, sold in the United States as Lovaza) vs. placebo. All patients had preexisting CV disease (MI, stroke, or revascularization in 59%) or CV risk factors at baseline. Patients were also randomized to open-label insulin glargine vs. standard care (with results reported in a companion publication). These groups were pooled for the primary analysis of the effects of omega-3 supplementation.
At median follow-up of 6.2 years, there were no significant differences between groups in CV mortality (9.1% vs. 9.3%) or all-cause mortality (15.1% vs. 15.4%). There were also no significant differences in fatal and nonfatal MI, fatal and nonfatal stroke, heart failure–related hospitalization, or revascularization procedures. Omega-3 supplementation was associated with significant reduction in triglyceride levels (P<0.001), but had no significant effect on other lipid levels. In subgroup analyses, supplementation had no significant effect on CV mortality in either the insulin-glargine or the standard-care group.
Alan Ehrlich, MD, is a deputy editor for DynaMed, in Ipswich, Mass., and assistant clinical professor in Family Medicine, University of Massachusetts Medical School in Worcester.
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