Monday October 22 2007
Does aspirin work differently in men and women?
Aspirin is good for the heart, but mostly if you are a man, reported the Daily Express. “The benefits of taking the drug to ward off heart attacks have been well documented but studies suggest the protective effects are mainly experienced by men”, the newspaper said.
The newspaper story is based on data from a review of studies where aspirin was used to prevent heart attacks both in people who have never had heart problems and in those who have. The researchers found that overall aspirin reduces the risk of non-fatal heart attacks, but appears to do this only in studies where the participants are predominantly male.
Anyone who has had been prescribed aspirin should not stop taking it on the basis of these results and before taking regular doses of aspirin, people should consult their doctor. More studies are needed before the implications for patients are known.
Where did the story come from?
Drs Todd Yerman, Wen Gan, and Don Sin from the University of British Columbia, the James Hog Centre for Cardiovascular and Pulmonary Research, and St Paul’s Hospital in Vancouver conducted this research. The study was funded by the Canadian Institutes of Health Research, the Canadian Lung Association and the Heart and Stroke Foundation of Canada. The review is not fully published yet, but is available in a draft form online through the BioMed Central medical journal – BMC Medicine.
What kind of scientific study was this?
This was a systematic review of randomised controlled trials. The researchers pooled together the results of multiple studies that looked at the use of aspirin to prevent a first heart attack (primary prevention) both in people with risk factors for cardiovascular disease and those without, or where aspirin was used to prevent another cardiovascular event in those who have had a heart attack or stroke (secondary prevention).
The researchers were interested in whether the gender of people who took part in the studies was responsible for the variation that is seen in the results. They combined the results from studies that involved mainly women and those that involved mainly men to see whether there were differences in the prevention of non-fatal and fatal heart attacks using aspirin.
What were the results of the study?
The researchers found that when all the studies were pooled together, aspirin reduced the risk of a non-fatal heart attack by 28% overall. When they grouped the studies by the predominant gender of their participants, they found that in the studies that mainly involved men, the reduction in risk was greatest – 38%, while in studies enrolling mainly women, the reduction in risk was 13% (and this was not statistically significant).
What interpretations did the researchers draw from these results?
The researchers concluded that gender accounts for a lot of the variation that we see in the efficacy of aspirin in reducing heart attacks. They say that their findings support the idea that women “might be less responsive to aspirin than men”.
What does the NHS Knowledge Service make of this study?
The take-home message is that anyone currently prescribed aspirin, particularly those in high risk groups, should not stop taking it. Anyone concerned about their heart and considering the regular use of aspirin should consult their doctor.
There are several points to keep in mind when interpreting this study:
- The researchers combined studies that looked at using aspirin to prevent a heart attack in people who had never had an event or heart disease (primary prevention) and also in those who were trying to prevent another event (secondary prevention). These are very different groups of people and it may not have been appropriate to combine them. People who have heart disease or have had a previous cardiovascular event are obviously at higher risk of a/another heart attack.
- Though researchers took into account the age and smoking status of the people in the studies, however, there are other factors which may also explain their findings. A person’s cardiovascular risk is often a combination of several factors including their previous history of an event, family history, age, blood pressure, cholesterol and diabetes. Being male is in itself a recognised risk factor. Whether the participants had other diseases (comorbidities) that may have changed the effects of aspirin is another factor. The researchers themselves say that 27% of the variation in study results could be accounted for by gender. This study doesn’t take into account all the other factors that make up the remaining 73% of the variation.
- Recent studies have shown that there are biological differences in the structures of heart vessels in men and women and in the pattern and nature of diseases. It is right to expect that there may be differences in the way drugs are metabolised and therefore differences their effects. Before it is certain that there are gender differences with respect to aspirin, however, further studies that are designed to detect these differences must be conducted.
- The systematic review does highlight the importance of considering gender when designing studies.
Links to the headlines
Aspirin is good for the heart… if you’re a man. Daily Express, October 22 2007
Men 'benefit most from aspirin'. The Guardian, October 20 2007
Aspirins ‘better for men’. Daily Mirror, October 22 2007
Aspirin ‘best for men’. The Times, October 22 2007
Aspirin is a 'man only' fix. The Sun, October 22 2007
Links to the science
Original study Yerman T, Gan WQ, Sin DD. The influence of gender on the effects of aspirin in preventing myocardial infarction. BMC Med 2007, 5:29
Further reading There are several reviews in the Cochrane library which consider the effects of aspirin for cardiovascular events, including:
Lip GYH, Chung I. Anticoagulation for heart failure in sinus rhythm. Cochrane Database Syst Rev 2000, Issue 2
Keller TT, Squizzato A, Middeldorp S. Clopidogrel plus aspirin versus aspirin alone for preventing cardiovascular disease. Cochrane Database Syst Rev 2007, Issue 3