Among patients with diabetes without evidence of cardiovascular disease, there was no significant difference in the risk of serious vascular events between those who were assigned to receive omega-3 fatty acid supplementation and those who were assigned to receive placebo, according to results from A Study of Cardiovascular Events in Diabetes (ASCEND), published in the New England Journal of Medicine. 

For this study, researchers randomly assigned 15,480 patients with diabetes but without evidence of atherosclerotic cardiovascular disease to receive 1-gram capsules containing either omega-3 fatty acids or matching placebo daily. The primary outcome was a first serious vascular event (i.e., non-fatal myocardial infarction or stroke, transient ischemic attack, or vascular death, excluding confirmed intracranial hemorrhage). The secondary outcome was a first serious vascular event or any arterial revascularization. 

During a mean follow-up of 7.4 years (adherence rate, 76%), a serious vascular event occurred in 689 patients (8.9%) in the fatty acid group and in 712 (9.2%) in the placebo group (rate ratio, 0.97; 95% confidence interval [CI], 0.87 to 1.08; P=0.55). The composite outcome of a serious vascular event or revascularization occurred in 882 patients (11.4%) and 887 patients (11.5%), respectively (rate ratio, 1.00; 95% CI, 0.91 to 1.09). Death from any cause occurred in 752 patients (9.7%) in the fatty acid group and in 788 (10.2%) in the placebo group (rate ratio, 0.95; 95% CI, 0.86 to 1.05). There were no significant between-group differences in the rates of non-fatal serious adverse events, researchers said. 

The Global Organization for EPA and DHA Omega-3s (GOED) said the study was not adequately powered, noting the most consistently demonstrated and reported benefit associated with omega-3s is the reduction in risk of cardiac death, which includes death from coronary heart disease (CHD). In the ASCEND study there were fewer vascular deaths in the EPA/DHA group than in the placebo group, as seen in exploratory analyses (additional analyses that are not part of the original statistical plan). Additionally, the authors reported a 21% risk reduction for coronary death that missed statistical significance (95% CI = 0.61-1.02). Given that the study was not powered to detect such a difference, this finding should not be overlooked.

 

GOED also noted this is the first time that results from any significant primary prevention research on omega-3s have been published. Although it is important to not over-interpret findings from post-hoc analyses, the results showed promise for prevention of cardiac death. The results reported were qualitatively consistent with existing research, most of which has focused on secondary prevention: a small trend toward the prevention of cardiovascular events, and a larger effect in the prevention of cardiac death. While more research is needed, this could indicate the mechanisms that underlie cardiovascular prevention as measured in secondary prevention may also be present in primary prevention, and help protect diabetics.   
 

Additionally, GOED said the baseline Omega-3 Index of 152 patients in a randomly selected subgroup whose Omega-3 Indexes were tested was relatively high (placebo treatment: 6.6% and omega-3 treatment: 7.1%). These patients are very different from the general adult U.K. population, for whom the average omega-3 index is less than 4%. While omega-3 treatment increased the Omega-3 Index to 9.1%, the high baseline Omega-3 Index suggests study participants were already close to the range of Omega-3 Index (8-12%) that is optimal for cardiovascular prevention, so it is to be expected that an additional dose of omega-3 would only have a modest effect.