Research finds little evidence to back aspirin for heart disease prevention

In a report published in Medscape Medical News, a new meta-analysis of trials evaluating aspirin for primary prevention of cardiovascular disease has found no overall benefit.

While aspirin use was associated with a lower risk of cardiovascular events, it increased risk of major bleeding, and had no effect on cancer risk.

However, there still appears to be some disagreement on how to apply these findings.

“A review of the evidence for use of aspirin in primary prevention was last looked at 5 or 6 years ago but now we have additional data from three new trials published last year – ARRIVE in people at higher CV risk, ASCEND in people with diabetes, and ASPREE in older individuals,” lead author of the new meta-analysis, Dr Sean Zheng, from King’s College Hospital in London, said.

“This new analysis was done to bring together the total evidence on aspirin in primary prevention of cardiovascular disease now available in a mixed population,” he said.

“We found that aspirin did reduce cardiovascular events by a modest 11 per cent, with a number needed to treat to prevent one event of 265, but it also increased major bleeding, such as a serious gastrointestinal bleed, intracranial bleed or bleed needing hospitalization or transfusion, by 43 per cent. That is a number needed to harm of 210,” Dr Zheng reported.

“These numbers needed to treat for benefit and harm are of similar magnitude,” he said.

“So there isn’t a clear-cut benefit, and in order to make a decision each patient would have to be considered individually with their own personal view of how they value these benefits and risks. But at the population level, we can say this is not strong enough evidence to recommend use of aspirin routinely.”

The meta-analysis was published online in JAMA earlier this month.

Dr Zheng explained that the earlier trials of aspirin for primary prevention tended to include all levels of cardiovascular risk – true population studies – but as these did not show a clear benefit, the later trials have tried to select out higher risk groups.

“But the results are similar across the board – aspirin appears to reduce cardiovascular events but increases bleeding to a similar degree in all groups,” he said. “We can never disengage the benefit from the risk.”

Guidelines Not Consistent

What effect will this latest meta-analysis have on guidelines?

Dr Zheng noted that UK and European guidelines generally do not recommend aspirin for primary prevention, but some of the US guidelines still recommend it based on age or cardiovascular risk, and there are a large number of patients in the US still taking aspirin for primary prevention.

“I think the US guidelines should change to not routinely recommending aspirin in primary prevention for any group, and our data should help in that regard,” he said.

Australian guidelines do not recommend aspirin for general primary prevention. However, medical advice may differ from the general guidelines if patients have heart disease or have had a stroke.

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