The Oxford University professor who made the headlines this week with his aspirin study – which demonstrated that the painkiller reduces the risk of cancer by 20 per cent – wasn’t telling the whole story. Just three years ago he discovered the drug was a major cause of stroke in the elderly.

His earlier findings may be the reason why Prof Peter Rothwell, at Oxford’s Department of Clinical Neurology, wasn’t as emphatic about taking aspirin as his cancer study warranted.

After announcing the findings, he cautioned: “I don’t think it’s necessarily right for the person who did the research to say what guidelines should be. We can’t say with absolute certainty that there won’t be some unknown harm in taking aspirin for 30 years…people have to accept there’s some uncertainty here.”

But there isn’t really any uncertainty. Prof Rothwell has already demonstrated that aspirin has caused a sevenfold increase in stroke over the past 25 years among elderly patients. At the time, he warned that aspirin could soon replace high blood pressure (hypertension) as the leading cause of stroke, especially among the over-75s.

He might also have had in mind a study from Eastern Virginia Medical School which discovered the drug is killing 20,000 Americans a year from gastro-intestinal bleeding – when the official records put the figure at just 59.

(Sources: Lancet, 2010; doi: 10.1016/S0140-6736(10)62110-1 – cancer study; Lancet Neurology, 2007;6: 487-93 – stroke study; Proceedings of the Annual Scientific Meeting of the American College of Gastroenterology, October 15, 2007 – GI deaths study).

via Aspirin reduces cancer risk, but raises chances of stroke, says same researcher | What Doctors Don’t Tell You.