Should aspirin for primary prevention be dosed by weight?

There's no evidence it will help reduce vascular events in people over 70kg

Low-dose aspirin might protect only low-weight patients from cardiovascular events, a major study suggests.

Compared with placebo, daily aspirin 75-100mg reduced the risk of vascular events in patients weighing less than 70kg by 23%, according to a pooled secondary analysis of seven randomised controlled trials (RCTs) of aspirin for primary prevention, covering 75,000 people.

But for people weighing 70kg or more, there was no evidence of its benefit in reducing vascular events, said the authors from the University of Oxford and Harvard Medical School.

“Findings were consistent in men and women, in participants with diabetes, and in trials of aspirin in secondary prevention of stroke,” they said.

“That 75-100mg aspirin was ineffective in primary prevention of cardiovascular events in the 80% of men and nearly 50% of women who weighed 70kg or more in our study ... questions the use of once-daily low