We can all recite the common the causes of a heart attack - smoking, diabetes and raised blood pressure and cholesterol, to name most of them - and yet up to half of people who suffer a heart attack don't have any of these risk factors.

Well, that's been the general view that has reached the status of urban myth. Except that it just isn't true, as two major studies of heart attack victims have revealed.

In one, up to 87 per cent of 21,000 people who suffered a fatal heart attack had at least one of the major risk factors. Of those who had a non-fatal attack, 92 per cent of men and 87 per cent of women had one or more of the risk factors.

A second study, which explored the health profiles of 122,458 heart patients, came up with similar findings. Researchers found that 85 per cent of women and 80 per cent of men with heart disease had one of more of the risk factors.

Of course, this does not explain the 20 per cent who did not have any of the risk factors, nor does it necessarily confirm that the so-called risk factors actually caused the heart attack. So perhaps this is one urban myth that cannot be laid to rest quite yet.

(Source: Journal of the American Medical Association, 2003; 290: 891-7, and 898-904).