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Yvain comments on Living Forever is Hard, or, The Gompertz Curve - Less Wrong

46 Post author: gwern 17 May 2011 09:08PM

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Comment author: Yvain 19 May 2011 12:56:25PM *  23 points [-]

The meta-analysis you cite is moderately convincing, but only moderately. They had enough different analyses such that some would come out significant by pure chance. Aspirin was found to have an effect on 15-year-mortality significant only at the .05 level, and aspirin was found not to have a significant effect 20-year-mortality, so take it with a grain of salt. There was also some discussion in the literature about how it's meta-analyzing studies performed on people with cardiac risk factors but not bleed risk factors, and so the subjects may have been better candidates for aspirin than the general population.

The Wikipedia quote you give is referring to secondary prevention, which means "prevention of a disease happening again in someone who's already had the disease". Everyone agrees aspirin is useful for secondary prevention, but there are a lot of cases where something useful for secondary prevention isn't as good for primary. In primary prevention, aspirin doesn't get anywhere near a tenth reduction in mortality (although it does seem to have a lesser effect).

I would say right now there's enough evidence that people who enjoy self-experimentation are justified in trying low-dose aspirin and probably won't actively hurt themselves (assuming they check whether they're at special risk of bleeds first), but not enough evidence that doctors should be demonized for not telling everyone to do it.

Comment author: LukeStebbing 17 January 2012 03:12:12AM *  1 point [-]

Aspirin was found to have an effect on 15-year-mortality significant only at the .05 level, and aspirin was found not to have a significant effect 20-year-mortality, so take it with a grain of salt.

Can you provide your reference for this? I looked at the meta-analysis and what I assume is the 20-year follow-up of five RCTs (the citations seem to be paywalled), and both mention 20-year reduction in mortality without mentioning 15-year reductions or lack thereof.

Edit: Never mind, I found it, followed immediately by

the effect on post-trial deaths was diluted by a transient increase in risk of vascular death in the aspirin groups during the first year after completion of the trials (75 observed vs 46 expected, OR 1·69, 1·08–2·62, p=0·02), presumably due to withdrawal of trial aspirin.

I'd like to see 20-year numbers for people who maintained the trial (and am baffled that they didn't randomly select such a subgroup).

Comment author: LukeStebbing 17 January 2012 05:32:09AM 0 points [-]

The meta-analysis you cite is moderately convincing, but only moderately. They had enough different analyses such that some would come out significant by pure chance.

Their selection methodology on p32 appears neutral, so I don't think they ended up with cherry-picked trials. Once they had their trials, it looks like they drew all conclusions from pooled data, e.g. they did not say "X happened in T1, Y happened in T2, Z happened in T3, therefore X, Y, and Z are true."