On Fri, 17 Sep 2004 23:27:08 +0000 (UTC), "PK"
<[email hidden]> wrote in message
<[email hidden]>:
Quoted message said:What gives many people difficulty is the intellectual gyrations some try to
go through to prove from ultra tenuous data that helmets provide no
protection and are more dangerous than not wearing one.
Talk about risk compensation, possible worsening of rotational
injuries, failure to mitigate rotational injuries - this is all
speculation, and inevitable because nobody has successfully
established why it is that the hospital based studies yield such
enormously different results from the real world. Other than the
obvious caveats about their structure, such as the fact that voluntary
helmet-wearers are likely to be more risk-averse (the most extreme
example of this sampling bias is probably the 1989 Thompson, Rivara
and Thompson study).
My view is that there are small-scale studies which show substantial
benefit, and large-scale figures which show no benefit at a population
level (in terms of serious & fatal injuries, which are the stats
collected by Governments). One of my reasons for being suspicious of
the likes of Cook & Sheikh is that, when challenged to account for
this disparity, their response is to repeat the mantra "helmets
prevent injuries" - or to deny that the disparity exists, or to
repudiate the suggested mechanisms for the disparity as with Towner
et. al. as if that somehow makes it go away. Not good enough.
The people with the time and money to find out what is really going on
are apparently all too busy trying to prove one side of the argument,
rather than accepting and studying the documented fact that in real
populations of cyclists, helmet use appears to have no effect on
serious & fatal head injuries.
It would be strange if there were no circumstances where a helmet
cannot migrate an injury from one side to the other of some arbitrary
line which defines a serious injury. It would be equally perverse to
suggest that helmets are more likely to prevent a brain injury than a
cut or graze (which is what at least two of the hospital studies
appear to suggest). I am not convinced that a helmet can worsen a
rotational injury, although I am sure that this has not been properly
studied. And I am not inclined to believe that cyclists alone among
road users are not subject to risk compensation. I am very confident
that New Zealand, for example, provides a reliable indication that
forcing people to wear helmets has no effect on their safety.
One of the things which really winds me up, is when a letter in the
press, or a posting on Usenet, or a feedback on my website, presents
the latest output from known helmet zealots (Cook & Sheikh again being
a leading example) as if this is the final clinching proof that
helmets are a necessary safety measure. Because in every case what
they are doing is to repeat the same studies, albeit in different
locations, repeating the sampling bias, and still failing to
acknowledge or address the fact that nowhere in the world have cyclist
injuries improved with increasing helmet use.
I do know from my own work that cycling is not uniquely productive of
head injuries in children, and I do believe that the best way to
improve cyclist safety is for more people to cycle. I also know that
the most survivable crash is the one which you avert - and it seems
that a majority of cyclists who die of head injuries have other mortal
injuries as well - so I am pretty confident that reducing stupid
behaviour like riding without lights, zooming on and off the pavement,
riding ill-maintained bicycles and so on, would have a massively
greater effect on cyclist casualties than all the helmet campaigns
ever devised.
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk
88% of helmet statistics are made up, 65% of them at Washington University
