Just zis Guy, you know? wrote:
> On Sat, 19 Jun 2004 10:59:23 -0400, Mark & Steven Bornfeld DDS
> <[email protected]> wrote in message
> <[email protected]>:
>
>
>>I posted the link of a review of
>>previously published clinical studies.
>
>
> That'll be where you went wrong, then. Epidemiological studies based
> on whole population data (including series where there are substantial
> step-changes in helmet use over very short periods, like in Australia)
> show no discernible benefit. Small-scale prospective studies show
> benefit, but often fall apart under investigation due to basic errors.
> Injury Prevention has just published a critique of one such paper by
> Cook & Sheikh; they mistook percentages for percentage points (a
> fairly basic statistical error) - if you correct this they are saying
> that helmets are 186% effective, with every helmet protecting not only
> its wearer but somebody else as well - this clearly demonstrates that
> there are major confounding factors in the data for which they have
> not accounted.
Let me see if I get this straight. All the studies showing a benefit
have fatal flaws; all the studies that show no benefit are well-designed.
The studies I saw cited are all retrospective studies. I believe it is
possible that somewhere a paper may have been published that confuses
percentages for percentage points. It is hard to believe this happened
multiple times in referreed journals.
Let me be clear--I am not an expert in safety data nor in epidemiology.
But I am up to my eyeballs in newsgroup pundits (in unrelated fields)
making patently ridiculous claims about the body of evidence in fields
in which I do have expertise. It is impossible for me to evaluate
helmet data for myself, nor have I found it prudent to believe folks
such as yourself who may very well have that expertise.
One hopes that people in position of authority choose carefully in whom
they listen to when policy is made.
>
> Many of the clinical papers are actually just literature reviews, with
> remarkably few actual studies, of which the best-known is Thompson,
> Rivara and Thompson's 1989 paper in the New England Journal of
> Medicine. The flaws in that study are well-documented (it arrives at
> a figure of 85% effectiveness by comparing poor solo urban street
> cyclists with middle-class families on bike paths and attributes the
> entire difference in injury rates to differences in helmet use).
See, I'm going to have to look up that paper. It is very, very
difficult for me to believe that NEJM would publish a paper with a flaw
that blatant.
It
> is still quoted as gospel by almost every "new" paper and literature
> review, and I have only once or twice seen any explicit mention of the
> known flaws in the study. In fact, if you replace the "control" group
> with Rivara's own street counts from the previous year, the supposed
> benefit vanishes. BHSI still quote it, despite knowing that it is
> wrong, because the figure is "so ingrained in the injury prevention
> community" that to use another figure would be "unhelpful". Unhelpful
> to whom? Those seeking to make the case for compulsion? Or those
> seeking to form a balanced judgement based on theevidence?
>
> By the way, according to BHSI this thread is not happening ;-)
>
>
> The fact that head injury rates have risen by 40% in the USA in a
> period when helmet use rose from 18% to 50% surely tells us something.
Are we talking about cycling head injuries, or total head injuries?
>
> As does the fact that the pro-helmet British government has admitted
> that it knows of no case where cyclist safety has improved with
> increasing helmet use.
I'd love to hear some context.
>
>
>>It is certainly understandable to me that racers who'd become
>>accustomed to the wind in their hair would object to the "intrusion" of
>>the insurance companies. Certainly there had been no studies back then
>>demonstrating the uselessness of helmets in preventing serious injuries,
>>but those I spoke to (some of whom you undoubtedly know personally) were
>>just as opposed to mandated helmets as you are now.
>
>
> That was not, in my opinion, an actuarial judgement; there was not
> enough data to go on at the time. Quite why a device designed for a
> crash at around 12mph should be mandated for racing is an interesting
> philosophical question.
Actually in this area you have a point. It was a decision made for the
USCF by whichever insurance carrier was willing to write the liability
policy. Far be it from me to tell you their decisions are made on the
basis of good, rational data. ;-)
HPV races now have helmets mandated. I have
> never seen an HPV racer sustain a head injury in a crash. Several
> helmeted wedgie racers have died and been brain injured in recent
> times, though.
>
>
>>Krygowski (and perhaps you) can probably name some safety measures that
>>you would acknowledge will decrease death and morbidity from bicycle
>>accidents.
>
>
> Only about 10% of cyclist injuries are to the area covered by the
> helmet and many (possibly most) cyclists who die of head injury also
> have other mortal injuries. Most fatal cyclist injuries are of course
> sustained in crashes involving motor vehicles: it is motor traffic,
> not cycling, which is dangerous.
Statistically you are right of course. But we are talking about
cycling; we might have much more to talk about were this a political or
automotive ng. But I know of several folks who have suffered head
injury, a couple of which were life-threatening (prolonged coma and
permanent neurological damage) without the benefit of motor vehicles.
>
> Any "safety programme" which ignores these fundamental facts is
> necessarily going to be of limited effect.
>
>
> The first, best thing that can be done to improve cyclist safety is to
> promote cycling. There is robust evidence from around the world that
> risk falls as participation increases, for a variety of reasons.
>
> The best thing a cyclist can do to ensure their own safety is to ride
> confidently and in a vehiclular style, as per Effective Cycling (and
> the equivalents in other countries such as Cyclecraft).
>
> If you look at detailed returns on crashes you find recurrent themes:
> cyclist injured by turning goods vehicle after the cyclist has gone up
> the inside at a junction; cyclist hit by car emerging from junction
> (which can be reduced by riding further out so you are where the
> driver is looking); cyclist hit by overtaking car which turns across
> their path (which can be reduced by riding further out, as the
> overtaking manoeuvre is then more deliberate and reminds the driver
> that you are there, rather than simply cruising by).
>
> And of course a cyclist should ensure that their bike is well
> maintained, with brakes and steering in good order.
>
>
>
> The biggest problem with helmet promotion is that it reinforces the
> perception of cycling as dangeorus without teaching any of the
> techniques which reduce the danger. In doing so, it actively deters
> cycling, which paradoxically /increases/ risk.
Clarification please: are you talking about relative risk to the rider,
or total risk to the population?
>
> Now, I would not normally care too much about people who decide to
> promote helmet use, if it weren't for the studies which show that it
> deters cycling - but these days the only thing stopping some
> jurisdictions from passing a helmet law is low levels of helmet use.
> More than one Government has said that compulsion will be introduced
> when voluntary wearing rates are high enough (at least they've learned
> that much from Australia, where cycling was decimated by compulsion).
>
> So the Liddites
I must complement you on this usage!
have persuaded Gvernments that every person who wears
> a helmet is voting for compulsion. That is unacceptable.
>
> My objections to helmet compulsion are not libertarian, but
> evidence-based. We have the experience of laws in Australia, New
> Zealand and Canada to draw on. In no case did injury rates reduce.
> In every case cycling was deterred.
As long as this is not libertarian, and allowing that proper bicycle
maintenance and effective cycling are more important to cyclist safety,
what would your feelings be about:
1) Mandatory licensing of cyclists (as per motor vehicles)
2) Mandatory minimum age for cyclists on public streets and roads
3) Mandatory registration of bicycles and periodic bicycle inspections
>
>
>
> But of course, these are unwelcome messages. When you compare child
> head injury rates for road crashes you find that pedestrians and
> cyclists have around the same proportion of head injuries, and
> pedestrian injuries are much more numerous (the risk levels in
> off-road cycling for children are an order of magnitude lower). Any
> justification of cycle helmet promotion applies to a much greater
> extent to walking helmets. And even more so for car occupants, whose
> fatality rate from head injuries is much greater.
Another clarification please: The head injury rates for cyclists vs.
pedestrians vs. auto passengers are for 1) Mile traveled
2)total number in population 3) hour spent in activity
What to do?
> Clearly the answer is to reduce the danger which cars pose to other
> road users, but that is politically unacceptable. Cycle helmets give
> the impression of "doing something" without the need to offend the
> motor lobby, which is politically very attractive.
I think that making the auto industry the focus in this discussion in
very much the same way makes it too easy to absolve ourselves of
responsibility in this issue. I certainly agree with you about the
relative danger of autos. I also agree that doing anything meaningful
in this area will be difficult (although the increase in the price of
crude oil is doing more than the political will would allow--if a
sustained rise in gasoline prices leads to diminished sale of SUVs, I
would be very happy). But if we wish to appear to be "doing something",
it is not enough to fault those who think helmet laws will save us; we
must have the courage (and the political clout) to do something that
WILL be meaningful.
Best,
Steve
>
> 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
