Pop a pill and you’re cured. In media reporting it often seems as simple as that. Take aspirin daily and you won’t get cancer. Put more subtly, take aspirin and your chances of getting cancer are reduced by a finite amount.

Except they’re not. What we have is a body of evidence, being added to over the months and years by new studies, but not evidence of the kind that allows a straightforward ‘positive’ result.

The Daily Telegraph says a daily dose will cut cancer risk for the over-60s by 40 per cent, but that is not what the evidence says. An academic article establishes an association between daily aspirin use and modestly reduced rates of death from cancer. But however much we might wish the relationship to be solid and causal, an association is all it is: the reduced death rate in the studies could be the result of some other, unobserved factor (people’s weight, their education and so on).

The admirable NHS Choices gives the detail and reaches the sober conclusion that ‘overall, the evidence is not strong enough to recommend that everyone take daily aspirin purely for cancer prevention’ — and that’s because we don’t know enough about the risks of taking aspirin, especially for people without cardiovascular complaints.

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