Benefits of aspirin outweighed by risk of bleeding

27 August 2018        

Category: Research

Aspirin prevents heart attacks in people with diabetes, but it causes almost as many major bleeds and should not be routinely prescribed to prevent first heart attacks, according to research that we've funded being presented at the European Society of Cardiology Congress in Munich.

an assortment of pills

Patients with diabetes are, on average, at increased risk of cardiovascular disease. Aspirin reduces the risk of second cardiovascular events and is already recommended for patients who have evidence of cardiovascular disease.

However, its role in preventing first events (primary prevention) is less clear because of the increase in bleeding. It has therefore been unclear whether aspirin should be recommended for cardiovascular prevention in diabetic patients without existing cardiovascular disease.

The ASCEND trial looked at whether aspirin reduced the risk of a first cardiovascular event in patients with diabetes. Between 2005 and 2011, 15,480 patients with diabetes but no history of cardiovascular disease were randomly assigned to aspirin (100 mg daily) or matching placebo. 

The researchers then recorded how many of the study participants suffered a heart attack, stroke or major bleed.

During an average of 7.4 years of follow-up, a first serious vascular event occurred in 685 (8.5%) participants allocated aspirin and 743 (9.6%) allocated placebo, which meant 11 of every 1,000 participants avoided a serious vascular event during the trial as a result of allocation to aspirin.

However, a first major bleed occurred in 314 (4.1%) participants given aspirin and 245 (3.2%) participants given a placebo, which meant that 9 of every 1,000 participants suffered a first major bleed during the trial as a result of allocation to aspirin.

Aspirin not recommended

Professor Jeremy Pearson, our Associate Medical Director, said:

“If you have a heart attack, your doctor will usually prescribe a daily aspirin to try and prevent a second attack. The reduced risk of a second life-threatening heart attack substantially outweighs the risk of side effects, such as bleeding. But there is still some debate over giving aspirin to people at high risk – such as those with diabetes – as a way of reducing the chances of that heart attack or stroke from happening in the first place. 

“This large clinical trial shows the benefit of taking aspirin to reduce the risk of a first heart attack or stroke is small, and it’s balanced by the increased risk of bleeding. Therefore it cannot be recommended.”