the usefulness of parachutes has not been scientifically tested

This post’s about another of the papers a teacher sent to me recently, with the subject line ‘science can be fun’. The title of this one is Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials (Smith & Pell, 2003). I have to say that I chuckled when I read this – a common charge levelled agains current medical practice by the ‘alternative health’ lobby is that many medical techniques haven’t been subjected to randomised controlled trials (with the corollary that it’s thus unfair to demand evidence from such trials on alternative practices).

And indeed this strikes me as an article written with tongue firmly in cheek. The authors state that they conducted a literature search of some of the major science sources: Medline, Web of Science, the Cochrane Library, and various others, using the search words ‘parachute’ and ‘trial’. However (& unsurprisingly), they found no randomised controlled trials (RCTs) of parachute use. Smith & Pell begin their discussion with the following inspired statement: It is a truth universally acknowledged that a medical intervention justified by observational data must be in want of verification through a randomised controlled trial. Many medical interventions probably fall into this category – for example, I doubt that surgery for severe appendicitis has ever been subjected to such a trial. That’s not to say that, where appropriate (& in the case of appendicitis it almost certainly isn’t!) such trials shouldn’t be performed. As Smith & Pell point out, hormone therapy for post-menopausal women seemed – on thebasis of observational studies – to convey a number of health benefits. But RCTs showed that hormone replacement therapy actually increased the risk of ischaemic heart disease.

As the authors point out, RCTs avoid a major weakness of observational studies: that of bias (eg selection bias & reporting bias). They note that individuals jumping from aircraft without the help of a parachute are likely to have a high prevalence of pre-existing psychiatirci morbidity (ie they are probably not in their right minds when they jump. You have got to love this paper!). So any study of parachute use could well be subject to selection bias, in that those using them are likely to have fewer psychiatric problems than those who don’t. Smith & Pell also put forward the possibiliy that enforced parachute use is simply a case of mass medicalisation of the population by out-of-control doctors – or worse, by evil multinational corporations 🙂 (These are, of course, charges frequently levelled at the medical world eg by those who are against interventions such as vaccination.)

This little gem of a paper (& I continued to chuckle as I read it) contains some valuable lessons on the nature of science (& more particularly, science-based medicine). And it should be read by anyone who doubts that scientists have both creativity and a good sense of humour.

G.S.S.Smith & J.P.Pell (2003) Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. British Medical Journal 327: 1459-1460.

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