Men 'benefit most' from aspirin

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The heart-protecting benefits of aspirin may be available mainly to men, Canadian experts have suggested.

Some research studies have suggested that the drug might cut heart attack risk by half.

But an analysis of trials involving 113,000 patients hinted those with a higher number of female participants were less likely to show benefit.

However, the BMC Medicine study was described as "potentially misleading" by one UK researcher.

We would caution clinicians on the prescribing aspirin to women, especially for primary prevention of heart attacks Dr Don SinJames Hogg iCapture Centre

Heart attacks happen when a narrowed or damaged blood vessel feeding the heart is blocked by a blood clot.

Aspirin can make it harder for these clots to form and studies suggesting this could prevent attacks, or make them less likely, have led to thousands of people worldwide taking the drug every day.

However, the precise benefit has been hard to gauge, with some research coming to the conclusion that it was unlikely to offer any protection whatsoever.

Physical differences

The researchers from the James Hogg iCapture Centre for Cardiovascular and Pulmonary Research, part of the University of British Columbia, believe that gender may be one of the main reasons for this.

It would be a tragedy if women who are taking it because they had already had a heart attack stop doing so Dr Colin Baigent, Clinical Trials Service Unit

They say that the make-up of a woman's heart and its surrounding blood vessels may be more resistant to the effects of aspirin.

They looked at the ratio of men and women taking part in major aspirin research projects - and found that those involving predominantly men were the most likely to find a benefit.

Conversely, those involving mainly women were more likely to find a lesser benefit, or none at all.

Dr Don Sin, one of the study authors, said: "We found that a lot of the variability in these trials seems to be due to the gender ratios, supporting the theory that women may be less responsive to aspirin than men for heart protection.

"From our findings we would caution clinicians on the prescribing of aspirin to women, especially for primary prevention of heart attacks.

"Whether or not other pharmaceutical products would be more effective for women is unclear; more sex-specific studies should now be conducted."

This is unlikely to be the last word on who should be taking aspirin - a study of 80,000 women published in March 2007 claimed to have found heart benefits for healthy women who regularly took aspirin.

Long-term aspirin use does raise the risk of internal bleeding and some doctors are reluctant to recommend it for people who have not already suffered a heart attack for this reason.

One UK expert, Dr Colin Baigent, from the Clinical Trial Service Unit at Oxford University, said that taking aspirin in the months and years after a heart attack delivered equal benefits to men and women.

He said: "This is potentially misleading - by far the largest trial included in this research was concerned mainly with the primary prevention of heart attacks - giving aspirin to people who had never had a heart attack.

"It would be a tragedy if women who are taking it because they had already had a heart attack stop doing so."