Bleeding risk with low dose aspirin outweighs benefit in primary prevention

Low dose aspirin should not be used for primary prevention in older people as it has no benefit and increases the risk of major bleeding events, an Australian RCT has shown.

The Aspirin in Reducing Events in the Elderly (ASPREE) trial compared the effects of 100mg daily aspirin and placebo in more than 19,000 healthy people over 70 in Australia and the US.

The participants, who had no cardiovascular disease at baseline, showed no differences between aspirin and placebo in risk of a first heart attack or stroke and disability-free survival over a five year follow up.

In a series of three papers published in NEJM, the trial investigators also showed that aspirin use was associated with a significant increase in in the number of cases of serious haemorrhagic events (3.8%) compared to the placebo group (2.8%).

The rate of major haemorrhage was 8.6 events and 6.2 events per 1000 person-years for aspirin and placebo, respectively (hazard ratio, 1.38).

Gastrointestinal bleeding accounted for almost half the major haemorrhagic events. The higher risk of upper gastrointestinal bleeding with aspirin than with placebo was particularly pronounced (hazard ratio, 1.87). The risk of intracranial bleeding was also higher with aspirin than with placebo (hazard ratio, 1.50).

There was also a small increase in mortality rates for aspirin use,  with a risk of death from any cause of 12.7 events per 1000 person-years in the aspirin group and 11.1 events per 1000 person-years in the placebo group (hazard ratio, 1.14).

Principal investigator Professor John McNeil, head of Monash University’s Department of Epidemiology and Preventive Medicine said the trial findings show that many older people may be taking aspirin unnecessarily and there needs to be a rethink of global guidelines relating to aspirin use for prophylaxis.

“These findings will help inform prescribing doctors who have long been uncertain about whether to recommend aspirin to healthy patients who do not have a clear medical reason for doing so,” he said

Professor Garry Jennings, a cardiologist and Chief Medical Adviser at the Heart Foundation said the trial addressed an important health question about the balance of risks and benefits for aspirin in preventing clots but increasing bleeding risk.

“There is no more conclusive evidence of this issue than ASPREE which was well powered to clarify the risk vs benefits and conducted in an exemplary fashion,” he said.

“The results support the present Heart Foundation position that aspirin is not recommended for people without a history of heart disease.  The present recommendations for people with heart problems to take aspirin on the advice of their doctor remain.

“ASPREE substantially clarifies the question of who should take aspirin and who should not and will thereby help save lives and prevent needless bleeding complications including stroke.

The trial investigators said the small increase in deaths observed in the aspirin group was primarily from cancer, and may be a chance finding since other large aspirin studies had suggested it may prevent cancer over the longer term.

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