New study on helmet effectiveness

This sub-forum all discussions about this "lively" subject. All topics that are substantially about helmets will be moved here, if not placed here correctly in the first place.

Vorpal
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Re: New study on helmet effectieness

Postby Vorpal » 22 Sep 2016, 8:56am

A similar literature review by Elvik a couple of years ago found:
-significant bias in the available literature
-earlier studies found more benefit than recent studies

His conclusion was very different; that there is little evidence that populations of adult cyclists benefit from increased helmet wearing. He did find some benefit for children.

The abstract doesn't say what were the crieria for inclusion. I will see later if I have access to the full text somewhere. Otherwise, someone else will have to access it and report back to us.

edited to add reference: Elvik R. Accident Analysis & Prevention, 2011;43(3):1245-1251
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Captain Morgan
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Re: New study on helmet effectieness

Postby Captain Morgan » 22 Sep 2016, 9:42am

The literature search produced 2405 total results of which 1190 were duplicates. A title and abstract search eliminated a further 1125 records; 91 full-text articles were assessed for eligibility and 48 studies did not meet study criteria. The primary reasons for exclusion were: the inability to construct a 2 x 2 table of injury by helmet status; the study data were a subset of data used in an included study; collected data were a case series; injuries were self-reported; the published report was an abstract only; helmet data were unreliable; and there was conflicting information in the paper. A further three studies were not included in a meta-analysis as there were too few helmeted cyclists to reliably estimate odds ratios. The 40 studies included in the metaanalysis comprised 64 708 injured cyclists and 89 total effect sizes (28 head, 30 serious head, 17 face, 12 neck and 2 fatal head injuries). By contrast, the most recent review by Elvik included data on 19 580 cyclists from 20 studies.


One reason given for this study being an improvement on Elvik is:
the assessment of publication bias requires an independent review of the research literature by two authors, and this is not possible when there is a sole author


I have the paper here, so can provide any/all of the information in it.

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661-Pete
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Re: New study on helmet effectieness

Postby 661-Pete » 22 Sep 2016, 9:56am

Oh dear!
Australian researchers say.....
says it all really.

I am unconvinced. I feel that other, motorised road users who can see the whole of my head and face, and see me dressed in ordinary clothes, tend to grant me more respect, seeing me as a person, than they would a fully lycra'd, begoggled, and helmeted cyclist, who seems to them as merely an obstruction....

But that's my view, based on my personal cycling experience which admittedly is hardly a properly controlled study.
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Re: New study on helmet effectieness

Postby Vorpal » 22 Sep 2016, 10:18am

Captain Morgan wrote:
The literature search produced 2405 total results of which 1190 were duplicates. A title and abstract search eliminated a further 1125 records; 91 full-text articles were assessed for eligibility and 48 studies did not meet study criteria. The primary reasons for exclusion were: the inability to construct a 2 x 2 table of injury by helmet status; the study data were a subset of data used in an included study; collected data were a case series; injuries were self-reported; the published report was an abstract only; helmet data were unreliable; and there was conflicting information in the paper. A further three studies were not included in a meta-analysis as there were too few helmeted cyclists to reliably estimate odds ratios. The 40 studies included in the metaanalysis comprised 64 708 injured cyclists and 89 total effect sizes (28 head, 30 serious head, 17 face, 12 neck and 2 fatal head injuries). By contrast, the most recent review by Elvik included data on 19 580 cyclists from 20 studies.


One reason given for this study being an improvement on Elvik is:
the assessment of publication bias requires an independent review of the research literature by two authors, and this is not possible when there is a sole author


I have the paper here, so can provide any/all of the information in it.


But Elvik wasn't a sole author. He used new techniques (developed in 2001?) to look at a previous literature review by multiple authors. He also discussed the addition of several new studies since the previous review.

What I would like to know, in particular are whether the studies by Thompson, Rivara and Thompson are included. Not only do some of their studies have significant problems, but they also suffer from a possible conflict of interest.
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Re: New study on helmet effectieness

Postby Captain Morgan » 22 Sep 2016, 10:32am

Two studies with that author list are included in the data, from 1989 and 1996, and a report was also referenced:
In a Cochrane Review, Thompson et al. included studies that collected data prospectively, injuries were medically verified and analyses controlled for selection bias, observational bias or confounding.

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Re: New study on helmet effectieness

Postby Stevek76 » 22 Sep 2016, 10:41am

Method:
...Time trends and publication bias were assessed....

Results:
...There was no evidence of time trends or publication bias....


Riiight. Any claims that there is no publication bias makes the whole thing exceptionally dubious. Publication bias is something that plagues pretty much every area of research.

Pity the paper is not open, it would be interesting to see if, like the thompson et al study (think it was this one?) this one shows helmets also have benefits to extraneous body parts like legs.

Did find this from the same authors though: https://www.researchgate.net/publication/291554175_Evidence_bicycle_helmets_mitigate_intra-cranial_injury_is_not_controversial

wahoofish
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Re: New study on helmet effectiveness

Postby wahoofish » 22 Sep 2016, 11:19am

Brilliant


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Re: New study on helmet effectiveness

Postby bovlomov » 22 Sep 2016, 11:22am

wahoofish wrote:Brilliant

Do us a favour and explain your glee.

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Re: New study on helmet effectiveness

Postby bovlomov » 22 Sep 2016, 11:27am

Am I allowed to post a Guardian comment?

thelonggrass
22 Sep 2016 11:16
0 1


The data on helmets is led from the hospital looking out. Definitely from this point of view helmets help. In the UK we might reduce cyclist fatalities from 113 to around 60-70. However there are 25 million bike owners in the UK, and 3.6m cycling at least once a month. So at a typical cost of a helmet of £30, compulsory helmets would cost the population between £110m-£750m. So the first question is that value for money, or could we improve cyclist safety better by spending £100m on something better?

Secondly, the view from the hospital out ignores the exposure rate. So it fails to consider the risk per individual or per individual journey. The UK has about 9000 hospital admissions for cyclists per year of which 2,800 are serious injuries with 110 fatalities. This is from a population of 3.6m regular/occasional cyclists (may actually be 6.6m). So one estimate of the likelihood of being KSI because of not wearing a helmet is about 0.04% per year - ignoring cycling time and journey length. Accidents are also disproportionally likely for those under 14 and over 65 and those cycling more adventurously (mountain bikes or racing). These are not high levels of risk (there were 30 fatalities related to angling in 2011 as a comparison), and may be better dealt with in other ways - reducing the factors that cause accidents for instance.

It also ignores a problem that requiring helmets may reduce the amount of cycling (I've seen estimates of a 13% drop in journeys). Since for cycling there is a safety in numbers effect - more cyclists leads to fewer accidents - so forcing helmet use might not be a positive trade off against other benefits from cycling itself. For example there were 9,500 estimated deaths in London from air pollution. Bikes on the road would reduce the car fumes that aggravate asthma and other lung problems so the net cost of discouraging cycling could be many times higher than the reduction in fatalities.

Since adults continually have to balance and judge risks, my feeling is that the scale of the problem is small for the relative burden that would be imposed, and so it is better to let cyclists choose.

I think s/he explains it rather well.

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Re: New study on helmet effectiveness

Postby Vorpal » 22 Sep 2016, 11:42am

I looked at the study linked on research gate, and what the authors did in that study was...

Previous research has found bicycle
helmets protect against head and upper facial injuries [4-8], and researchers have studied
associations between helmets and neck injuries [4, 8]. Therefore, when assessing bicycle helmet
efficacy, the selection of controls should not include cyclists with head, face or neck injuries. This is
an important distinction as the probability of multiple injuries could differ substantially between
helmeted and non-helmeted cyclists and therefore bias statistical results.

there were 35 helmeted and 99
non-helmeted cyclists with intra-cranial injuries, and 227 helmeted and 208 non-helmeted cyclists
with no head, face or neck injuries. Using this data, helmet use is associated with a 68% significant
reduction in the odds of intra-cranial injury (OR=0.32, 95% CI: 0.21-0.50, p<0.001).


Frankly, I think it is probable that cyclists without any head, face, or neck injuries will have been in less serious crashes than those with them. Although I understand the problem that they are trying to address, and I think the concern is a valid one, I don't think that their approach holds water, at least not without discussing the probable difference in severity between accidents. Selecting controls on the basis of injury type is certain to introduce bias.
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Re: New study on helmet effectiveness

Postby pjclinch » 22 Sep 2016, 11:46am

I'll dig it out of the library when I've a spare moment, but immediate thoughts are it's another meta-study, so going over stuff that has all the problems outlined by Goldacre and Spiegelhalter in their 2013 BMJ editorial, and indeed stuff that contributed to that editorial being written. Meta-analysing a lot of studies with contentious methodologies doesn't strike me as a great way to get meaningful data.

That you can go over available studies where many suggest a benefit and most of the rest come up with nothing much and come up with a net benefit is news at about the level of "Bear excrement identified in Colorado forest". In the meantime this sort of thing is used as a basis to criminalise many people who choose a healthy travel option.

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Re: New study on helmet effectiveness

Postby bovlomov » 22 Sep 2016, 12:14pm

pjclinch wrote: In the meantime this sort of thing is used as a basis to criminalise many people who choose a healthy travel option.

Perhaps this kind of headline grabbing research supports your views about the general direction of the helmet debate. That is, that any amount of research, in either direction, about helmet efficacy, or about risk, weight, heat and balance issues, all distracts from the fact that helmets are a near irrelevance in the debate about cycling safety.

Someone asked in an earlier thread: what if there was a helmet that was proved to be effective? (or something along those lines). My answer was that it wouldn't make any difference to me. I don't wear one for the same reason that I don't wear any number of other safety aids. The risk is low, and the effort, cost and inconvenience of wearing one isn't worth it, in an environment that I consider to be safe enough. Even if this paper had published 100% effectiveness, I wouldn't wear one, because I can't run my life on the basis that I may be among the 60 or 70 people a year in the UK that may be saved by such a device. And, if something is to be done about cycling safety, helmets aren't it.

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Re: New study on helmet effectiveness

Postby 661-Pete » 22 Sep 2016, 12:32pm

If you'll forgive the little digression:
I read somewhere, that King Charles 1st made arrangements, and paid in advance, to have his head sewn back on after his unfortunate encounter with the axeman in 1649. This was apparently, in order to ease the passage of his 'immortal soul' into heavenly paradise, or some such line of thinking.

I perceive a sort of analogy with helmet-wearing, if you please. You may be stretchered into hospital (or mortuary) stiff, cold and unresponsive, with a broken neck, but the lid on your cranium 'saved' you from intolerable brain injuries....
Suppose that this room is a lift. The support breaks and down we go with ever-increasing velocity.
Let us pass the time by performing physical experiments...
--- Arthur Eddington (creator of the Eddington Number).

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Re: New study on helmet effectiveness

Postby Flinders » 22 Sep 2016, 12:43pm

There is always the elephant in the room- people who were wearing helmets which did their job properly in an accident and whose wearers therefore didn't end up in A&E at all. I know of a few of those. That's very difficult to count, though I know they try to.