I have written in this column before of the "wonder drug" characteristics of aspirin. For a medication over 100 years old, it continues to astonish doctors with its range of preventative medical benefits. Aspirin has been shown to prevent cancer of the colon and rectum.
Although not yet conclusively proven, aspirin is likely to show benefit in both the main causes of dementia - Alzheimer's disease and dementia due to narrowing of the arteries. Prostate cancer is the latest condition to show a possible benefit. There is also a suggestion that aspirin can help prevent cataracts.
In the heart and the circulatory system, aspirin benefits are now well proven. A recent conference at the Royal College of Surgeons in Dublin heard the latest findings on aspirin and the heart.
Dr Giovanni de Gaetano reported on the results of the Primary Prevention Project (PPP), a large Italian trial which investigated the effectiveness of low-dose aspirin in preventing heart problems in people with one or more risk factors for heart disease.
Some 4,500 people were given 100 mgs of aspirin a day for more than three years and the effects were then measured. There was a significant reduction in the number of deaths from a cardiovascular cause as well as a reduction in heart attacks among the trial participants.
Every one of the 4,500 enrolled in the trial had at least one cardiovascular risk factor when they started taking aspirin. So, the patients were one of the following: over 65; they had elevated blood pressure; their cholesterol was in excess of 6.4 mmol/l; they had diabetes; they were clinically obese; or they had a family history of heart attack in a close relative.
The trial results, which will be published soon in the leading medical journal, the Lancet, represent strong evidence that both women and men with at least one cardiac risk factor should take a daily low-dose aspirin tablet.
Prof Peter Elwood of the University of Wales College of Medicine spoke on the topic: "You and your heart: should you be on aspirin?".
He told the meeting the benefits of aspirin in the prevention of heart attacks and strokes have been shown in more than 170 scientific trials. "The proportional reduction in heart attacks and strokes by aspirin is virtually the same in every group of individuals. The risk of an event is reduced by between 30 and 40 per cent - in males and females, in older and younger folk, in patients with diabetes and in those without," he said.
So, shouldn't we all just take an aspirin a day, regardless of whether or not we carry a risk factor for cardiovascular disease?
The answer, according to Prof Elwood, is no. The reason for the apparent contradiction lies in the number of heart attacks and strokes prevented in different groups of patients. In every 100 men who have had a recent heart attack, about 10 are likely to suffer another attack or die within the next year. However, if they are all put on aspirin, three or four of these 10 heart attacks will be prevented.
On the other hand, if the entire population takes an aspirin a day, because most of us are healthy people with no cardiovascular risk factors, several thousand would have to take aspirin in order to prevent one heart attack.
It all comes down to a risk-to-benefit ratio. If you include the possible side effects of aspirin (principally the risk of bleeding from the stomach) then among those with cardiac risk factors the benefits of giving aspirin outweigh the risk. This is not the case where a healthy population is concerned. The risk of a stomach bleed from aspirin (one in a 100) outweighs the benefit of one heart attack prevented per thousand people taking the drug.
Unusually, the dose of preventative aspirin does not determine the actual benefit gained. There is no evidence of any difference in the degree of protection given by doses between 75 mg and 300 mg per day. The World Health Organisation recommends 100 mg per day. Probably the most important part is to take a tablet every day, rather than worrying about the exact dose. If your doctor is currently prescribing 300 mg a day and this suits you, then there is no need to change.
So should you be on aspirin for your heart? Prof Elwood summarised his advice like this:
If you have already had a heart attack or stroke: definitely yes and see your doctor if you are not already taking it. If you are at increased risk because of raised levels of risk factors, then: probably yes and you should see your doctor who will advise you.
Dr Muiris Houston can be contacted at mhouston@irish-times.ie or leave messages on tel 01-6707711, ext 8511, but he regrets he cannot reply to individual medical problems