Discontinuation of Low Dose Aspirin and Risk of Myocardial Infarction: Case-Control Study in UK Primary Care

Study Questions:

What is the impact of discontinuation of aspirin in patients taking it for secondary prevention?

Methods:

The authors used The Health Improvement Network (THIN) database in the United Kingdom to assess impact of aspirin discontinuation on the outcome of 39,513 patients, ages 50-84, with a first prescription for aspirin (75-300 mg/day) for secondary prevention of cardiovascular outcomes in 2000-2007. The mean follow-up was 3.2 years and the outcome of interest was nonfatal myocardial infarction (MI) or death from coronary heart disease (CHD). A nested case-control analysis was used to assess the risk of these events in those who had stopped taking low-dose aspirin compared with those who had continued treatment.

Results:

There were 876 nonfatal MIs and 346 deaths from CHD. Compared with current users, people who had recently stopped taking aspirin had a significantly increased risk of nonfatal MI or death from CHD (rate ratio [RR], 1.43; 95% confidence interval [CI], 1.12-1.84). This difference was driven by an increase in nonfatal MI (RR, 1.63; 95% CI, 1.23-2.14) with no difference in the risk of death from CHD (RR, 1.07; 95% CI, 0.67-1.69). Discontinuation of aspirin was associated with an excess of four more cases of nonfatal MI per 1,000 patients.

Conclusions:

The authors concluded that aspirin discontinuation in patients with prior cardiovascular disease is associated with an increased risk of nonfatal MI.

Perspective:

The benefit of aspirin for secondary prevention is well established, although there are little direct data to guide the common practice of lifelong aspirin in these patients. This study demonstrates an increase in MI with aspirin cessation and provides indirect support to continue aspirin long-term in this population. Further studies are needed to define the risk associated with this approach and to evaluate strategies to ensure continuation of aspirin in these patients.

Clinical Topics: Atherosclerotic Disease (CAD/PAD)

Keywords: Coronary Artery Disease, Great Britain, Myocardial Infarction, Follow-Up Studies, Cardiovascular Diseases, Primary Health Care


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