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I have never been excited about things like taking aspirin to prevent heart attacks as I have written about before (“Should I Take Aspirin or Put a Gun to my Head?“), and this week there is an article in Lancet that pretty much sums things up for me. The authors combined data from six large trials including 95,000 people who did not have heart disease who were taking aspirin for the prevention of heart attacks.
Taking aspirin was associated with a reduction to 0·51% aspirin vs 0·57% control per year in vascular events like heart attacks, due mainly to a reduction in non-fatal heart attacks (0·18% vs 0·23% per year). There was no effect on stroke (0·20% vs 0·21% per year). There was also no difference in death rates from heart attacks and strokes (0·19% vs 0·19% per year). Aspirin increased major gastrointestinal and extracranial bleeds (0·10% vs 0·07% per year, p<0·0001).
The others concluded that taking aspirin for prevention is of “uncertain net value”. In other words, useless. The meager savings from heart attacks is outweighed by dangerous bleeds, and it doesn’t save your life, so why bother?
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You may wish to be careful about your conclusions—it is rather important to distinguish primary prevention (asa probably not all that useful), vs secondary prevention (asa VERY beneficial).
so it means recommendations for primary prevention might change in the future.
as i recall, the primary prevention recs already don’t advise aspirin to the general public – only for those who are felt to be at higher risk for a first heart attack (but for whom aspirin’s benefits aren’t clear either that I know of).
Could Doug or someone translate the results into NNT numbers, for primary and secondary prevention of MIs, fatal and non-fatal?
Thanks!
for primary prevention, if one can use the meta-analysis data presented, the NNT is around 1667.
Secondary prevention numbers (not presented in this study) are significantly better.
and if my next back of the envelop calculation is correct, the NNT for secondary prevention of any serious vascular event in this meta-analysis was about 70.
I think I would agree with that. So the conclusion is that aspirin is useful for secondary prevention (translation: those with a history of heart attack, etc) but not primary prevention (preventing first heart attack). I had that in mind but did not make explicit in the post, thanks.
Oh BTW hat tip to Mrs. Bremner