Emailed to PP, following offline exchange:
> I am also heartily in favour of avoiding acrimony! Indeed, I
> was rather disappointed by the rather aggressive reactions my
> post accrued. This is a debate about important matters, you
> won't get any personal abuse off me. My goal is not to
> persuade, but merely to defend my position, and achieve a
> logically sound debate.
Usenet can be a good place for that, and uk.rec.cycling is less prone
to flamewars than most groups. But you have to avoid the obvious
traps, like walking in and posting an "of course helmets make sense!"
post without first considering whether, as a group of obviously
committed cyclists, we might not have spent at least a little bit of
time considering this matter ourselves
> Now, your response to my message was one of the better (if
> slightly aggressive) ones, since you took the trouble to
> include some statistics, but there were a few points I'd like
> to clarify with you...
Again, you are missing the history. The arguments have been rehearsed
many, many times. During the recent debate over Eric Martlew's helmet
bill there was a lot of discussion, and in opposing the bill, a lot of
us spent time getting our facts and arguments in order. Many of us
were originally strongly pro-helmet, some in favour of compulsion,
more in favour of compulsion for children. And almost all of us who
started with that opinion have changed our view based on the evidence,
kept quiet by the Liddites, which indicates that in the real world
helmets make no measurable difference.
> Twenty years ago, I fell over the handlebars of my bike and
> struck my head on the road, causing mild concussion. I was
> not wearing a helmet. Subsequently, I have partial anosmia,
> and some of the motor control on my left side is impaired.
Logical fallacies: statistical syllogism (false extension of the
specific to the general).
"Helmet saved my life" anecdotes (or, in this case "helmet would have
saved my life") are, in the main worthless. I have a "knitted acrylic
balaclava saved my life" anecdote - the truth is, without going back
and repeating the crash you cannot know if the helmet would have made
it better, made no difference, or made it worse, by making the head
bigger. There is also good evidence to suggest that helmeted cyclists
are more likely to hit their heads in the first place. That's why
personal experience - anecdotal evidence - has to be discounted in
favour of more robust evidence based on large populations, not least
because we cannot quantify how mouch more likely it is that the
helmeted rider will crash in the first place.
> Fortunately, the consequences are merely inconvenient. A
> helmet would probably have reduced the injuries I experienced
> since its shattering would have absorbed some of the anterior
> G-forces I experienced and that led to neurones being
> stretched longitudinally to snapping point, and to minor
> haemorraghing.
A helmet which shatters has simply failed. Polystyrene foam absorbs
very little energy in brittle failure; it is designed to absorb energy
by crushing. And as stated above, modern medical thinking downplays
the role of straight coup/contre-coup brain injury, suggesting that
closed-head brain injuries are much more likely to be the result of
torsional forces, which helmets of course cannot mitigate.
Further reading: The efficacy of bicycle helmets against brain injury;
Curnow WJ 2003. Accident Analysis and Prevention: 2003; 5.2.03
> Many years ago, when leaving work, one of our neuropsychology
> postgraduates commented upon the helmet that I had bought
> recently. I mentioned that I didn't wear it much because it
> was not very comfortable and I was too self-conscious. He
> then pointed out that he had recently met a patient at the
> local neuro ward who had been a senior executive, due for
> promotion to a national level post; he had taken his daughter
> out for a ride on her new bike. Sadly, he was hit by a car
> and suffered brain damage that left him in permanent need of
> 24 hour care. The student advised me that a helmet would have
> reduced the severity of his head injury. Since then, I have
> worn my helmet as often as possible.
Logical fallacy: appeal to authority.
You'd rather believe a med student than the evidence of the entire
cycling population of New Zealand? Have you considered that the med
student might have been in the grip of "true believerism"? Have you
not realised that the average crash involving a motor vehicle yields
energies which exceed the rated capacity of a Formula 1 helmet?
Anybody who makes an absolute statement like "a helmet *would* have
reduced the severity of this man's injuries" should be distrusted on
principle. The true statement was "in my opinion, a helmet may have
reduced the severity of this injury" - and even then he would struggle
to find any evidence, because in cases involving motor vehicles there
is essentially no credible evidence of effectiveness. The sample
sizes of the pro studies are too small, and the results of the studies
based on large populations show no effect.
You must also take account of the existence of experts who take a
contrary view, based on good science.
> It would be improper for me to drag these people into the
> debate.
Logical fallacy: anonymous authority.
Just as it would be improper to drag into the debate the brain surgeon
recently featured on TV, repeatedly shown riding his bike with no
helmet. The experts are as divided as the rest of us. Dr Aziz Sheikh
is an ardent compulsionist, still convinced that he is right even
though his maths have been shown to be wrong. Dr Richard Keatinge is
a former consultant epidemiologist who is equally convinced that there
is no credible evidence to support any effect on serious or fatal
injuries. Barry Pless, editor of Injury Prevention, ridiculed the
idea of risk compensation, until his own study proved that it happens.
There are no easy answers. So the correct position is to live and let
live, to oppose compulsion for many excellent reasons, and to
challenge anybody who makes a dogmatic statement to prove it.
You would know all this if you had researched the group archive on
Google.
> However, I am sure you can accept that surrounded by
> such emminent people, I have access to fairly reliable
> information when it comes to brain injury prevention. They
> are not experts on *accidents*, but their knowledge on these
> matters is obviously considerable.
No, you are surrounded by people who might well all think the same
way, but who (a) might not be fully aware of the balancing evidence
(which is kept very quiet by the Liddites) and (b) are contradicted by
equally eminent experts who disagree.
The BMA's position is that helmets should not be compulsory.
Interventionist medical journals have all been riding the helmet
bandwagon since Thompson,. Rivara and Thompson, and the impression of
benefit remains long after the critiques are out. Many doctors
accepted uncritically the idea that helmets prevent 85% of head
injuries and 88% of brain injuries, although that clearly implies
that, uniquely among personal protective equipment, they are more
effective in the most serious injuries than in trivial ones. People
will believe almost anything if it is in line with their
preconceptions.
Further reading: "Trust us,. we're experts"
<url:http://www.prwatch.org/books/experts.html>
>>> Cycling increases the probability and severity of injury,
>>> including head injury, compared to my usual activities.
>> Prove it.
> I would say "Why should I?", given it was only a personal
> viewpoint, but I didn't make that clear in the post. So,
> would you accept that I am more at risk when cycling than
> when allotment gardening, visiting friends on foot,
> biological surveying, and hill walking, since those are my
> usual activities?
You stated it as fact. So you either have to prove it, or acknowledge
that it is conjecture. My analysis of hospital admissions indicates
that you are wrong.
Most serious and fatal cycling head injuries in children (the
population I have analysed) happen on the roads, the rate being around
ten times that for off-road cycling. The head injury rate of road
cyclists and pedestrians is not significantly different. Both are
higher than off-road cyclists or the general population; cars are what
makes the difference. Car crashes account for one in ten injury
admissions but 50% of injury deaths, so this is hardly a surprise:
most injury deaths are due to head injury, this applies to all impact
deaths. And, as the manufacturers to admit and the testers agree,
their product is not specified for crashes involving motor traffic.
Most head injury admissions are the result of simple trips and falls,
by the way.
> I was comparing my risk when cycling with my risk when doing
> my own alternative activities. The data you quote is quite
> irrelevant to my situation, though I accept it is informative
> for the bigger picture.
I am comparing your risk when cycling along a road to your risk while
using it as a pedestrian (on the footway). The risk is, within
reasonable limits, identical. Do you consider a helmet necessary
while walking along a road? If not, your position is illogical.
Google for Wardlaw's BMJ paper if you don't believe me. The Japanese
have even experimented with walking helmets for children, but they
didn't make any difference either.
> the
> neuropsychologists here have dealt with numerous patients who
> were cyclists with head injuries. I would not presume to
> question their judgement.
The helmeted community is not big enough and the crash numbers also
not big enough for any single unit to be able to come up with
conclusive data either way. Using population level figures, such as
those from New Zealand and Australia, shows no benefit.
> It might be useful to you to know that (I am advised that)
> the typical cause of head injury when cycling is going over
> that handlebars due to mechanical failure or hitting
> obstacles.
I have done that once, and survived unscathed. I know of two
seventy-year-olds who had similar crashes, one died, the other did
not. The survivor was the one without the helmet. Once again,
anecdotal evidence is useless.
We had this discussion recently on one of the newsgroups. The
consensus was that going over the bars, although serious, is actually
exceptionally rare, with the possible exception of serious offroad
riding. The inability to distinguish between Mrs. Miggins pottering
down to the shops on her Raleigh 3-speed and Jack the Lad tackling
some extreme downhill on his full-sus special is one of the things
which undermines the Liddite case.
There is also inbuilt bias. A pro-helmet doctor sees an injured,
helmeted cyclist and thinks that they have done their best to protect
themself, their injuries would surely have been worse without the
helmet; it is forgotten. An injured unhelmeted cyclist is remembered
and reported as yet another tragedy of people who refuse to take
sensible precautions. But still he sees both helmeted and unhelmeted
cyclists...
Much is made of the cyclists whose helmets "saved their lives" in
crashes in races. Less is made of the two cyclists this year who died
despite wearing helmets. Cyclists dying during races is extremely
rare, yet two have died this year, both of head injuries, and both
wore helmets. How can that be? And the answer may well be risk
compensation. I believe that 100% of the riders who have died in
races this year were wearing helmets at the time, and that the death
toll is already higher than for the last couple of years before
helmets were mandated by UCI. But again, the sample is too small to
tell anything - other than the obvious selective memories of Liddites.
> Unfortunately, many of the accidents were
> unpredictable -- forks collapsing/quick-releases coming
> undone (arguably predictable, but to err is human), and
> animals/children/objects coming unexpectedly into one's path,
> etc. Forewarned is forearmed.
Talk to James Annan about forks coming undone and QR failures. They
are less unpredictable, and for different reasons, than you might
think.
If you are genuinely concerned about this kind of crash, you have no
option but to campaign for the outlawing of those upright abominations
and compulsory use of recumbent bicycles. I guarantee that the
numbers of over-the-bars incidents would drop like a stone.
>> Same in ceertain states in Canada. In the USA head injury
>> rates have increased by 40% as helmet use has increased
>> from 18% to 50%.
> I do not accept that this tells me a helmet does not reduce
> my risk of brain injury, which was the point of my message. A
> correlation does not show cause-effect, and proves nothing,
> especailly here where the relationships are multi-factorial,
> though I admit it is suggestive.
A correlation does not show effect, but if the effect was anything
like it is claimed to be the many and various correlations and lack of
correlations - all of which show either no change or increasing risk
with increasing helmet use - would simply not be possible. There is
no known case where cyclist safety has improved with increasing helmet
use. And I didn't say that, the (pro-helmet) road safety minister
did.
To discount this evidence as you apparently do is the converse of the
"from ignorance" logical fallacy: because something is not known to be
true it is assumed to be false.
>>> Brain damage can result in permanent, wide-ranging,
>>> profound, and extremely unpleasant problems.
>> Logical fallacy
> I am completely stumped by this. A logical fallacy is an
> error in a syllogism, but you quoted a premise only! I'm not
> sure what specifically you think is a fallacy.
