medwireNews: Findings from a phase IV trial suggest that aspirin use may reduce the risk for primary vascular events but at the cost of increased major bleeding risk in patients with diabetes, while omega-3 fatty acid supplementation does not have a cardioprotective effect.
As reported at the European Society of Cardiology Congress in Munich, Germany, and published simultaneously as two articles in The New England Journal of Medicine, the ASCEND (A Study of Cardiovascular Events in Diabetes) investigators randomly assigned 15,480 patients with type 1 or type 2 diabetes and no evidence of cardiovascular disease to receive aspirin at a dose of 100 mg per day or to receive placebo. In a factorial design, participants were also randomly allocated to take 1 g capsules containing either omega-3 fatty acids or olive oil once daily.
In the aspirin part of the study, Jane Armitage (University of Oxford, UK) and colleagues found that 8.5% of participants in the aspirin group experienced a first serious vascular event – defined as a composite of nonfatal myocardial infarction, nonfatal ischemic stroke or transient ischemic attack, or death due to vascular causes (with the exception of intracranial hemorrhage) – over an average 7.4 years of treatment. By comparison, 9.6% of their placebo-treated counterparts had a first serious vascular event over the treatment period, giving a significantly reduced rate ratio (RR) of 0.88 in favor of aspirin.
Therefore, “[a]spirin use prevented serious vascular events in persons who had diabetes and no evident cardiovascular disease at trial entry,” say the researchers. They emphasize, however, that aspirin “also caused major bleeding events” in these patients.
Indeed, major bleeding events (any confirmed intracranial hemorrhage, sight-threatening bleeding in the eye, gastrointestinal bleeding, or any other bleeding event that was fatal or required hospital admission or transfusion) were significantly more common among patients treated with aspirin versus placebo, with rates of 4.1% versus 3.2% (RR=1.29). The majority (41.3%) of bleeding events were gastrointestinal.
Based on the absolute difference in event rates between the groups, 91 patients would need to be treated to avoid one serious vascular event over 7.4 years, and 112 would need to be treated to cause one major bleeding event, explain Armitage and team.
Therefore, “[t]he absolute benefits [of aspirin treatment] were largely counterbalanced by the bleeding hazard,” conclude the study authors.
In the omega-3 part of the study, a comparable 8.9% of patients in the fatty acid group and 9.2% of those given olive oil experienced a serious vascular event over the follow-up period (RR=0.97). Similarly, the rates of the composite outcome of a serious vascular event or revascularization did not differ significantly between the two groups, at 11.4% versus 11.5% (RR=1.00), and neither did the incidence of death from any cause, at 9.7% versus 10.2%, respectively (RR=0.95).
“These findings, together with results of earlier randomized trials involving patients with and those without diabetes, do not support the current recommendations for routine dietary supplementation with [omega-3] fatty acids to prevent vascular events,” say Louise Bowman (University of Oxford, UK) and co-investigators.
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