On Wed, 10 Nov 2004 23:49:41 -0000, Mark McN
<
[email protected]> wrote:
>Could you make it up? You could not. It's worth pointing out, and when
>I write my next letter I *shall* point it out, that the BMA appear to be
>guilty of making more inflated safety claims for helmets than the
>manufacturers do.
Please do exactly that. The person to write to is probably Dr Peter
Tiplady, chair of the public health committee who are responsible for
the whole sorry mess.
http://www.bma.org.uk/ap.nsf/Content/ptipladyCo
I urge moderation of language: the problem is that the person who
prepared the briefing got it wrong, and he therefore trusted an
inaccurate briefing. The fact that the balancing data will come from
sources outside Medline, and will therefore not be immediately obvious
to anyone without specialist knowledge of the subject, is worth noting
inna sympathy stylee.
My current draft follows:
The contents of the paper "Legislation for the compulsory wearing of
cycle helmets" by the BMA's Board of Science and Education has been
brought to my notice. I am concerned at the lack of academic rigour
shown in this document, as well as the apparent lack of openness in
its preparation. I am sure that many members of the BMA will be
unhappy about this, especially since the previous position paper,
based largely on the same evidence and following a much more open
process, came to such a dramatically different conclusion.
The paper itself repeats a claim which I have seen made by the Bicycle
Helmet Initiative Trust (BHIT), namely that "50 children die each year
of cycling related head injuries". This is a claim they have made
more than once, including on national television; the true figure is
not fifty but ten, a matter of public record (Hansard, following a
Parliamentary Question). I recently complained to the Advertising
Standards Authority (ASA) about this and other misleading claims made
in a BHIT leaflet. The complaint has been "informally resolved" and
they have undertaken not to repeat it.
You may be interested in BHIT's justification for quoting a figure
five times the actual value: it is an "estimate based on
under-reporting." As a senior figure in the medical establishment I
leave it to you to judge the merit of the idea that 80% of fatal child
cyclist head injuries should go unrecorded, and how quoting this
figure, so easily verified, might reflect on the BMA. I need hardly
say that the Transport Research Laboratory's figure for
under-reporting of cyclist fatalities - zero percent - is not
considered controversial.
Quite why this figure should be considered relevant is in any case
something of a mystery, as almost all fatal child cyclist injuries are
the result of impacts with motor vehicles; these greatly exceed the
limited protective capabilities of cycle helmets. The paper calls on
the ASA to prevent manufacturers making excessive claims, but on this
the manufacturers are admirably clear: the documentation with my own
helmet has a full page of caveats and warnings about the limited
protection offered. Surely the BMA is not trying to go further than
the manufacturers and suggest that helmets protect against car
crashes? References to deaths must be treated with great caution.
This is the claim of which I have most personal knowledge. I know
that other claims within the paper are also inaccurate, such as the
idea that a drop of one year in the minimum age for driving was the
cause of a 43% drop in cycling by teenagers in Victoria, Australia.
Overall the lack of cross-checking and balance is in stark contrast to
the previous position statement; it smacks of undue haste, possibly to
meet some external agenda. It is, however, understandable if the
paper was prepared by someone without specialist knowledge of this
particular field - much of the balancing data comes from sources
outside Medline such as national governments' transport casualty and
health statistics. There is a particular danger here in that many of
those who are apparently experts in the field are active in
campaigning for compulsion, so do not always provide the balancing
data in briefings. You are not the first to have tripped up on this!
It is a mistake to take the volume of studies and meta-analyses on
helmets as representing a consensus. Recent experience with MMR and
the link between HRT and coronary heart disease should remind us that
observational studies, on which the pro-helmet case is almost
exclusively based, must be treated with caution unless supported by
data from other, different types of studies; the other data in this
case comes from time series based on whole populations of cyclists,
which much larger data sets generally show insignificant or negative
benefit. This is a clear indication that we do not yet have anything
like enough knowledge of the mechanisms underlying crash and injury
causation to form an unequivocal judgment.
It is my fervent hope that the BMA will withdraw this publication
pending redrafting before further damage is done to its reputation,
and I would wholeheartedly support any call for work to be done to
establish why it is that the predicted and intuitively obvious
benefits of cycle helmets are not realised in the real world.
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
