26 May 2013

NNT, a very interesting number

While reading a somewhat dated article (that I'd highly recommend) that calls into question the wisdom of taking statins, I came across the measure known as NNT (number needed to treat). The NNT basically tells you how many patients would need to take a drug (or adopt some form of treatment) in order to obtain the desired outcome. When a drugs' effectiveness is analyzed using the NNT, the outcome can be very enlightening. In the article, Lipitor, used to prevent a heart-attack, had an NNT of 100! (In other words, 99 people taking this expensive drug for the observed period would receive no observable benefit whatsoever.) If we look at side-effects, on the other hand, the NNH (number needed to harm) is quite low (in other words, the side-effect would show up in even a small group of people taking the drug). I have some knowledge of statistics and am familiar with effect-size measures, but these measures--the NNT and NNH--are quite enlightening. If the NNT of common drugs is anything close to what it is for statins, it really suggests that Americans are popping way too many pills. Instead of wasting so much money on what is of little or no benefit (and is likely to harm us), we should relax, be happy, lose weight, meditate, laugh more, meet friends, have good sex, eat a few more veggies and fish, and cut out the red meat--all lifestyle changes that have been proven to be very effective.

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