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Aspirin, antioxidants not effective in primary prevention of cardiovascular events in patients with diabetes, study shows

Wednesday, November 05 2008 | Comments

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What's This? Aspirin and antioxidants do not appear to be effective in the primary prevention of cardiovascular events in patients with diabetes and asymptomatic peripheral arterial disease, concludes a randomized, controlled trial.

Clinical guidelines including those from the American Heart Association and the American Diabetes Association suggest that antiplatelet therapy is appropriate for the primary prevention of coronary artery disease in patients with diabetes; at the same time, publicity in the lay press about antioxidant deficiency among people with diabetes has led many people with the condition to supplement with antioxidants, noted a research team from Scotland.

To determine whether aspirin and antioxidant therapy, combined or alone, are more effective than placebo in reducing the development of cardiovascular events in patients with diabetes and asymptomatic peripheral arterial disease, they recruited adults from 16 hospital centers in Scotland. All participants (n=1,276) were aged 40 years or older and had type 1 or type 2 diabetes and an ankle brachial pressure index <=0.99 but no symptomatic cardiovascular disease.

The researchers randomized participants to receive 1 of 4 therapies daily: a 100 mg aspirin tablet plus an antioxidant capsule selected specifically for the study's purposes (n=320), aspirin tablet plus placebo capsule (n=318), placebo tablet plus antioxidant capsule (n=320), or placebo tablet plus placebo capsule (n=318). Randomized participants were followed for a median of 6.7 years.

The researchers set 2 hierarchical composite primary endpoints; death from coronary heart disease (CHD) or stroke, nonfatal myocardial infarction or stroke, or amputation above the ankle for critical limb ischemia; and death from CHD or stroke.

Because the researchers observed no interaction between aspirin and antioxidants for the composite primary endpoints, they compared the 2 groups randomized to receive aspirin with the 2 groups that did not receive aspirin, and the 2 groups randomized to receive antioxidants to the 2 groups that did not receive antioxidants.

The study produced no evidence to support the use of either aspirin or antioxidants in the primary prevention of cardiovascular events and mortality in individuals with diabetes. Overall, 116 primary events occurred in the aspirin groups compared with 117 events in the no-aspirin groups (18.2% vs 18.3%, respectively; hazard ratio [HR], 0.98; 95% CI, 0.76-1.26). Forty-three deaths from CHD or stroke occurred in the aspirin groups compared with 35 in the no-aspirin groups (6.7% vs 5.5%, respectively; HR, 1.23; 95% CI, 0.79-1.93).

A total of 117 primary events occurred in the antioxidant groups compared with 116 events in the no-antioxidant groups (18.3% vs 18.2%, respectively; HR, 1.03; 95% CI, 0.79-1.33). Considering death from coronary heart disease or stroke, there were 42 deaths in the antioxidant groups compared with 36 in the no-antioxidant groups (6.6% vs 5.7%, respectively; HR, 1.21; 95% CI, 0.78-1.89). (Belch J, et al. BMJ 2008;337:1840.)

"Although aspirin is cheap and universally available, practitioners and authors of guidelines need to heed the evidence that aspirin should be prescribed only in patients with established symptomatic cardiovascular disease,"  concluded Dr. William R. Hiatt, a professor of cardiovascular research at the University of Colorado Denver School of Medicine, in an accompanying editorial. (BMJ 2008;337:a1806.)

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