"judith" wrote in message
news
On Thu, 28 Aug 2008 17:33:35 +0100, "Michael C"
wrote:

Here you go again making statements without anything to back them up.
They
don't know very well that they are more likely to result in an overall
decrease in the chance of injury to the head, BECAUSE THERE HAS BEEN NO
EVIDENCE THAT SUGGESTS THAT.


Why do many Cycle Clubs recommend people wear them then?
Why do the Police insist that officers on cycles on duty wear them?

Are they wrong to do so?

Yes.

Are you saying that the sole reason you support compulsory helmets is
because some 'safety' organisations recommend them?

Are you saying that there is no evidence that cycle helmets will
overall reduce the chance of injury?

What about the BMJ article (D.L.Robinson) where I think from memory it
says that case-control studies show that cyclists who wear helmets
have fewer head injuries than non-helmet wearers - is this not the
case?

No. As has already been asked of you, if they reduced head injuries to such
an extent why have the countries that have adopted helmets not shown any
decrease in the amount of head injuries?

On Thu, 28 Aug 2008 19:57:53 +0100, "Michael C"
wrote:

snip

Why do many Cycle Clubs recommend people wear them then?
Why do the Police insist that officers on cycles on duty wear them?

Are they wrong to do so?

Yes.

Why are they wrong to *recommend* (not insist) that people should wear
them?

Do you not accept that there is clear evidence that wearing them
reduces the risk of injury?

Are you saying that the sole reason you support compulsory helmets is
because some 'safety' organisations recommend them?

No - but it reinforces my view. I do not accept that DfT, RoSPA, many
cycle clubs, and the police are wrong in recommending that people
should wear helmets.
(I accept that the compulsory side of the argument is not so clear)

(You are demonstrating the anti-compulsory-helmet denial trait that
helmets are not beneficial - because if we accept that they are, then
compulsion will come)

Are you saying that there is no evidence that cycle helmets will
overall reduce the chance of injury?

What about the BMJ article (D.L.Robinson) where I think from memory it
says that case-control studies show that cyclists who wear helmets
have fewer head injuries than non-helmet wearers - is this not the
case?

No.

What do you mean - No - that the article does not say it or that case
control studies do not show fewer injuries?

Do you also not believe as I have pointed out elsewhere from DfT
research:

Bicycle helmets have been found to be effective at reducing the
incidence and severity of head, brain and upper facial injury.
Bicycle helmets have been found to be effective in reducing injury for
users of all ages, though particularly for children.
All studies found evidence of a protective effect with regards to head
injury of helmet wearing in the event of a bicycle crash.

"judith" wrote in message
...
On Thu, 28 Aug 2008 17:41:19 +0100, "Michael C"
wrote:

DfT: Bicycle helmets: review of effectiveness

Here are some extracts - save you reading it all:

Bicycle helmets have been found to be effective at reducing the
incidence and severity of head, brain and upper facial injury.
Bicycle helmets have been found to be effective in reducing injury for
users of all ages, though particularly for children.
All studies found evidence of a protective effect with regards to head
injury of helmet wearing in the event of a bicycle crash.
http://www.dft.gov.uk/pgr/roadsafety...ct4726?page=18
(This is not the 1994 paper I was thinking of - it is later)

And that very same paper then says "While most studies indicate that helmets
offer protection from head injury, the relative risk of injury
in helmeted and unhelmeted bicyclists has varied in different studies."

So is it all studies or most studies? And once again - how come there isn't
a drastic reduction of injuries in the countries that adopted compulsory
helmets? And why do countries like Switzerland have a far lower useage of
helmets and also a far lower number of injuries?

I also don't see any mention of helmets increasing the likelihood of you
having an accident - why is this missing?

"judith" wrote in message
news
On Thu, 28 Aug 2008 19:57:53 +0100, "Michael C"
wrote:

Yes.

Why are they wrong to *recommend* (not insist) that people should wear
them?

Because it is a choice that is best left up to the rider.

Do you not accept that there is clear evidence that wearing them
reduces the risk of injury?

No, because there isn't. Why have countries like Switzerland had less
injuries alongside less helmet useage?

Are you saying that the sole reason you support compulsory helmets is
because some 'safety' organisations recommend them?

No - but it reinforces my view. I do not accept that DfT, RoSPA, many
cycle clubs, and the police are wrong in recommending that people
should wear helmets.
(I accept that the compulsory side of the argument is not so clear)

(You are demonstrating the anti-compulsory-helmet denial trait that
helmets are not beneficial - because if we accept that they are, then
compulsion will come)

"Many cycle clubs" DON'T recommend wearing or not wearing a helmet as well.

If helmets are so beneficial why have countries like Switzerland had less
injuries alongside less helmet useage?

No.

What do you mean - No - that the article does not say it or that case
control studies do not show fewer injuries?

Do you also not believe as I have pointed out elsewhere from DfT
research:

Bicycle helmets have been found to be effective at reducing the
incidence and severity of head, brain and upper facial injury.
Bicycle helmets have been found to be effective in reducing injury for
users of all ages, though particularly for children.
All studies found evidence of a protective effect with regards to head
injury of helmet wearing in the event of a bicycle crash.

Why have countries like Switzerland had less injuries alongside less helmet
useage?

On Thu, 28 Aug 2008 21:22:50 +0100, "Michael C"
wrote:

"judith" wrote in message
news
On Thu, 28 Aug 2008 19:57:53 +0100, "Michael C"
wrote:

Yes.

Why are they wrong to *recommend* (not insist) that people should wear
them?

Because it is a choice that is best left up to the rider.

I have said before - most riders do not have the time, the
inclination, or the ability to plough through the "evidence" -
therefore it is reasonable for established/authoritative bodies to
make recommendations.

Do you not agree?


Do you not accept that there is clear evidence that wearing them
reduces the risk of injury?

No, because there isn't. Why have countries like Switzerland had less
injuries alongside less helmet useage?

So you disagree with the findings of the DfT paper I have referenced
elsewhere - I see you chose to ignore that question when I asked it
previously.


Are you saying that the sole reason you support compulsory helmets is
because some 'safety' organisations recommend them?

No - but it reinforces my view. I do not accept that DfT, RoSPA, many
cycle clubs, and the police are wrong in recommending that people
should wear helmets.
(I accept that the compulsory side of the argument is not so clear)

(You are demonstrating the anti-compulsory-helmet denial trait that
helmets are not beneficial - because if we accept that they are, then
compulsion will come)

"Many cycle clubs" DON'T recommend wearing or not wearing a helmet as well.

If helmets are so beneficial why have countries like Switzerland had less
injuries alongside less helmet useage?

I have not seen that reported - please can you name the publication
where it can be found.

On Thu, 28 Aug 2008 21:19:05 +0100, "Michael C"
wrote:

"judith" wrote in message
.. .
On Thu, 28 Aug 2008 17:41:19 +0100, "Michael C"
wrote:

DfT: Bicycle helmets: review of effectiveness

Here are some extracts - save you reading it all:

Bicycle helmets have been found to be effective at reducing the
incidence and severity of head, brain and upper facial injury.
Bicycle helmets have been found to be effective in reducing injury for
users of all ages, though particularly for children.
All studies found evidence of a protective effect with regards to head
injury of helmet wearing in the event of a bicycle crash.
http://www.dft.gov.uk/pgr/roadsafety...ct4726?page=18
(This is not the 1994 paper I was thinking of - it is later)

And that very same paper then says "While most studies indicate that helmets
offer protection from head injury, the relative risk of injury
in helmeted and unhelmeted bicyclists has varied in different studies."

So is it all studies or most studies?

I don't know - I didn't write the report - if it's really worrying
you why not write and ask them?

And once again - how come there isn't
a drastic reduction of injuries in the countries that adopted compulsory
helmets?

I don't know - I accept that adding compulsion in to the research - I
am not the only one who cannot explain that.

And why do countries like Switzerland have a far lower useage of
helmets and also a far lower number of injuries?

I also don't see any mention of helmets increasing the likelihood of you
having an accident - why is this missing?

Go on then - I'll bite:

How about because there is no evidence that they do?

judith wrote:


I also don't see any mention of helmets increasing the likelihood of you
having an accident - why is this missing?

Go on then - I'll bite:

How about because there is no evidence that they do?


As you are happy to accept anecdotal evidence that " A helmet saved my
life" will you accept my anacdote?

On Thu, 28 Aug 2008 19:35:21 +0100, Marc
said in
:

I think from memory DL Robinson in the BMJ says that case-control
studies confirm that cyclists who wear helmets have less head injuries
than those who don't wear helmets.

Not good enough!

Indeed. What judith is doing is called quote mining. In this case,
she takes a single sentence, misquotes it, and uses it to completely
misrepresent the thrust of the paper.

Yes, case-control studies do suggest tat cyclists who choose to wear
helmets are also less likely to suffer head injury. Based on this,
helmet promoters assert that if everyone wears a helmet they will
become like those who choose to wear helmets. In this context a
helmet law maybe seen as a form of controlled experiment; you take a
population, change the variable which you say will produce X result,
and observe the outcome. Which was, in every case thus far, either
no reduction or in some cases a significant /increase/ in rates of
head injury.

So that shows, as Robinson's paper says, that the case-control
studies are simply documenting the existence of confounding factors.

This problem of observational studies is explained in some detail in
an issue of the International Journal of Epidemiology given over to
discussion of one notable case where the observational studies
turned out to be wrong in both magnitude and sign - that is, they
proposed a large benefit which turned out in controlled trials to be
a small but significant /dis/benefit.

Recommended reading here is:

* The hormone replacement - coronary heart disease conundrum: is
this the death of observational epidemiology? Lawlor DA, Smith GD &
Ebrahim S, International Journal of Epidemiology, 2004;33:464-467
* Hormone replacement therapy and coronary heart disease: four
lessons. Petitti D, International Journal of Epidemiology,
2004;33:461-463

The lessons drawn from this by these distinguished epidemiologists
we

* Do not turn a blind eye to contradiction. Do not ignore
contradictory evidence but try to understand the reasons behind
the contradictions.
* Do not be seduced by mechanism. Even where a plausible mechanism
exists, do not assume that we know everything about that mechanism
and how it might interact with other factors.
* Suspend belief. Of the researchers defending observational
studies, Pettiti says this: "belief caused them to be unstrenuous
in considering confounding as an explanation for the studies". Do
not be seduced by your desire to prove your case.
* Maintain scepticism. Question whether the factor under
investigation can really be that important; consider what other
differences might characterise the case and control groups. Do not
extrapolate results beyond the limits of reasonable certainty

I would say that judith has fallen into all four of these traps.

What is particularly tiresome is that her response to actual
analysis of the sources is to point to organisations who have failed
to adequately study the issue and assert that their ill-informed
opinion, because it matches hers, is somehow more valid than the
observed facts as presented by Robinson and others.

I fail to see how $SELFSELECTEDARBITEROFTRUTH saying that helmets
save lives is ever going to outweigh the documented fact that when
helmet wearing rates substantially increase in a short period, there
is absolutely no observable improvement in injury rates. For the
fallacy of this type of argument I recommend a study of Huntingdon's
account of R. v. Mare Anglorum in /Historia Anglorum/ (though this
account is disputed and does not appear in the contemporaneous
/Encomium Emmae/, it is nonetheless suitable for illustrative
purposes).

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

85% of helmet statistics are made up, 69% of them at CHS, Puget Sound

In message
judith wrote:

On Thu, 28 Aug 2008 19:51:16 +0100, Mike Clark
wrote:

In message
judith wrote:

On Thu, 28 Aug 2008 16:11:15 +0100, Mike Clark
wrote:
[snip]
Let me point you to a follow-up submission by the same author

http://www.bmj.com/cgi/eletters/332/7543/722-a#15405

In particular I would invite you to take a look at Figure 2 which
clearly indicates that from 96/97 to 01/02 the percentage of head
injuries decreased at the same time as the percentage of cyclists
wearing helmets also showed a marked decrease. This data shows that
an improvement (decrease) in the frequency of head injuries is
associated with a reduction in the proportion of cyclists wearing a
helmet.
[snip]


I believe I am looking at the graph which you referenced:


Fig 2 Linear Trends in %head injury, vs helmet wearing (%HW) of child
cyclists in Ontario, Canada.

To me this clearly shows the HI trend dropping almost linearly - with
no relationship to the HW graph.

Is that the graph which you are looking at?


Yep that is the one.

So I'm glad that you agree that it is evidence for no relationship
between helmet wearing and protection from head injuries.

You said : This data shows that an improvement (decrease) in the
frequency of head injuries is associated with a reduction in the
proportion of cyclists wearing a helmet.

It's a trick that I often use in supervisions with students to see if
they are really looking at the information and thinking it through for
themselves or simply listening to what I am saying and extrapolating too
far. I had deliberately selected from all the data in the figure those
points that were consistent with my statement.


It shows nothing of the sort. It purely shows that there was a steady
decrease in HI over the period under consideration - with no
correlation to the helmet wearing at all.

You correctly pointed out to me that if you included all the data you
came to a different conclusion. I quite agree with you that the data
shows no consistent correlation of cyclists injuries with helmet use.
Yet selected aspects of the same data sets have been used in earlier
publications to support the arguments for the protective effects of
helmets. That's why the later publications call into doubt some of the
earlier interpretations.


Why do you think the injuries do not go back up to their original (04)
level in 01/02?


I don't need to speculate on the cause in order to make use of the
observation. The observation is that cycle injuries don't seem to
correlate with helmet use. Data can be used to invalidate a hypothesis
more easily than to validate a hypothesis.

Mike
--
M.R. Clark PhD, Reader in Therapeutic and Molecular Immunology
Cambridge University, Department of Pathology
Tennis Court Road, Cambridge CB2 1QP
Tel +44 (0)1223 333705 Web http://www.path.cam.ac.uk/~mrc7/