The British Medical Journal has published a paper that has concluded that aspirin is ineffective in preventing primary cardiovascular events in some patients with diabetes. This study has been reported in the media (BBC).
The study particularly looked at patients with diabetes and asymptomatic peripheral arterial disease (defined as a ankle brachial pressure index of 0.99 or less). These patients were randomised to one of four treatment groups including treatment with aspirin, antioxidants or matching placebo. The primary outcome for the study was a composite including death from coronary heart disease or stroke, non-fatal myocardial infarction or stroke.
The study recruited almost 1,300 patients with approximately 300 in each treatment group and ran for 8 years. The study found no difference in the primary endpoint for either treatment. The paper notes that, "small effects may be shown with larger trials continued for a longer time".
It should be noted that by year 6 of the study one third of patients had died but that deaths from vascular causes comprised less than half of these deaths. The authors of the study propose that optimal use of statins (mean cholesterol in patients with diabetes has dropped from 6.0 mmol/l in 1996 to 4.3 mmol/l in 2007) may be one explanation for lack of efficacy of aspirin in this study. Additionally, primary prevention studies have generally added statins to standard therapy with aspirin; this study raises the question whether aspirin is still necessary if statins are used.
Action: In the secondary prevention of cardiovascular disease aspirin therapy is effective and remains part of standard care. The place of aspirin in primary prevention of cardiovascular disease is questioned by this study but more work is required to confirm these findings before changes to practice are implemented.
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