why is there not a definative study about helments?

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[XAP]Bob
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Re: why is there not a definative study about helments?

Postby [XAP]Bob » 11 Dec 2014, 7:34am

drossall wrote:What I want to know is whether the OP is any the wiser :D

Hopefully the answer is: yes - what is definitive? What for...
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Re: why is there not a definative study about helments?

Postby Phil Fouracre » 11 Dec 2014, 9:14am

Probably none the wiser! Just another 'helmet thread' effectively going nowhere.
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Re: why is there not a definative study about helments?

Postby pjclinch » 11 Dec 2014, 10:01am

Hopefully it's brought the Goldacre/Spiegelhalter editorial to greater prominence. While far from a definitive resolution one way or the other it is a useful thing to point out that we really don't know all the answers with current methods and data.

Not as useful as we might want, and it's not to say there's no point in looking at the data if you're so inclined to make better sense of it, or that we we don't know any answers, but it usefully suggests that not being sure is a reasonable position to take for now and at least some time to come.

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Re: why is there not a definative study about helments?

Postby MartinC » 11 Dec 2014, 10:02am

Phil Fouracre wrote:Probably none the wiser! Just another 'helmet thread' effectively going nowhere.


Yes, but that's the answer to the question in the OP.

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Re: why is there not a definative study about helments?

Postby Steady rider » 11 Dec 2014, 10:03am

why is there not a definative study about helments?

To try and answer the question. Data on head and other injury per hour cycled is needed and the accident rate various by about 10 to 1 depending on the type of cyclist/age/experience, so even if data is available it becomes difficult to compare.
Data indicates a lower head injury rate and higher accident rate.

Studies can be provided in various ways, gather injury data and compare wearers to non-wearers, problem here is they do differ in several ways and behavior is a prime function of accident involvement, it becomes difficult to reliably compare.

Studies of groups and population are also difficult in term of changes that occur, improved road safety, provision of cycling infrastructure, increased cycle training and having sufficient data on the level of cycle use and helmet use.

Multiple changes often occur and even if funding was available any study could have aspects of uncertainty.

Some Governments do not seem keen to fund studies showing that the helmet laws have discouraged cycling. The medical profession can use the easy studies of comparing without the risk per hour, so their results will always be weak.
Even helmet promotion and the focus on accidents may change behaviour.

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Re: why is there not a definative study about helments?

Postby martinn » 11 Dec 2014, 1:15pm

So the answer is (In my opinon) after having followed this thread....
its a bit too complicated with too many variables, and there is no interest in trying to do any better because, there are other areas of cycle safety which have a much more significant impact, for the amount of time, effort and money that would be required to answer the helmet question.
So the question of does the evidence support wearing a helmet is proably never going to be answered in a fashion that will be unequvical.
Which at the end of the day is more than a little fustrating,
Thank you for all your thoughts.

Martin

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Re: why is there not a definative study about helments?

Postby kwackers » 11 Dec 2014, 1:39pm

martinn wrote:So the answer is (In my opinon) after having followed this thread....
its a bit too complicated with too many variables, and there is no interest in trying to do any better because, there are other areas of cycle safety which have a much more significant impact, for the amount of time, effort and money that would be required to answer the helmet question.
So the question of does the evidence support wearing a helmet is proably never going to be answered in a fashion that will be unequvical.
Which at the end of the day is more than a little fustrating,
Thank you for all your thoughts.

Martin

You're assuming that it's actually possible to come up with a definitive answer.
IMO if such a thing were possible then population studies would show very marked trends, they don't and therefore there isn't going to be an answer simply because helmets make no appreciable difference.
That's the answer you're looking for, feel frustrated no more... ;)

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Re: why is there not a definative study about helments?

Postby Steady rider » 11 Dec 2014, 1:58pm

On helmet laws a definitive answer is probably achievable.
Piet de Jong in 2012 provided a way to evaluate the question whether mandatory bicycle helmet laws deliver a net societal health benefit . He reported, “In jurisdictions where cycling is relatively unsafe, helmets will do little to make it safer and a helmet law, under relatively extreme assumptions, may make a small positive contribution to net societal health.”

The formula for the cost benefit ratio is (mu x beta)/(e x q ), where
mu = odds of cycling is not maintained
beta = health benefit of cycling
e = proportional reduction in head injuries
q = proportion of accidents involving the head

The Handbook of Road Safety Measures detailed its findings on ‘Effects on injuries of mandatory wearing of bicycle helmets’ with;
• Increased use of helmets, Head injuries -25 (-30; -19)
• Increased risk per km cycled, All injuries +14 (+10; +17)
• Less cycling, All injuries -29 (-30; -28)
• Net effect, All injuries -22 (-23; -21)

Assuming values of 29% discouraged as reported, assuming 20 to 1 for health factor, e = - 0.25 as reported and q =0.3 matching general data (Whately 1985).

mu value is 0.408, using 0.29/1-0.29 = 0.29/0.71= 0.408
beta = 20
e = 0.25
q = 0.3
Cost benefit ratio is (0.408 x 20)/(0.25 x 0.3) = 8.16/0.075 =109

The cost factor against helmet laws is then more than 100 to 1. Put very simply, helmet laws are not worthwhile because the health loss is far greater than the possible gains. Applying the formula to adult and children would provide estimates for each group. The 14% extra accident figure is not included.

Even for helmet laws the figures would be disputed by a number of people who support helmets.

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Re: why is there not a definative study about helments?

Postby pjclinch » 11 Dec 2014, 2:47pm

martinn wrote:So the question of does the evidence support wearing a helmet is proably never going to be answered in a fashion that will be unequvical.
Which at the end of the day is more than a little fustrating,


I think the actualities of life are to complex to come up with questions with yes/no answers like that for a great many situations. You just can't come up with quantitative measures for faffing, image-conciousness, comfort etc. etc., which will inform the personal end decision for a lot of people.

The typical answer to a simple question like "should I wear a helmet to cycle?" almost inevitably has an answer of "it depends...", and the list of things it depends on is very long and has a lot of things that don't lend themselves to hard numbers.

It could be worse: if cycling turned out to be so dangerously mad an EN1078 hat was going to make any useful difference it may well be time to just take the bus...

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Re: why is there not a definative study about helments?

Postby TonyR » 11 Dec 2014, 8:09pm

Steady rider wrote:Studies can be provided in various ways, gather injury data and compare wearers to non-wearers, problem here is they do differ in several ways and behavior is a prime function of accident involvement, it becomes difficult to reliably compare.


But to repeat the point I made earlier, none of that would be a problem if the protective effect was as big as some claim. It's only because the effect is so small that it's difficult.

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Re: why is there not a definative study about helments?

Postby MartinC » 12 Dec 2014, 9:06am

We're all assuming we know what the question means. What's the question the OP wants a definitive answer to? How many live do helmets save? Do they provide a substantive safety benefit in mitigating injury? Should they be compulsory? etc. etc.

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Re: why is there not a definative study about helments?

Postby TonyR » 12 Dec 2014, 9:38am

pjclinch wrote:
martinn wrote:So the question of does the evidence support wearing a helmet is proably never going to be answered in a fashion that will be unequvical.
Which at the end of the day is more than a little fustrating,


I think the actualities of life are to complex to come up with questions with yes/no answers like that for a great many situations. You just can't come up with quantitative measures for faffing, image-conciousness, comfort etc. etc., which will inform the personal end decision for a lot of people.

The typical answer to a simple question like "should I wear a helmet to cycle?" almost inevitably has an answer of "it depends...", and the list of things it depends on is very long and has a lot of things that don't lend themselves to hard numbers.


Which is why it should be a matter of informed personal choice. But based on the overall population statistics you can say its almost certainly not worth wearing one for safety reasons. Of course there are exceptions. Just as the population statistics say you would be foolish to smoke, if you are suffering from a terminal disease with months left to live or you've just reached your 90th birthday then its highly unlikely that taking up smoking is going to kill you but that still does not mean its a good idea for most people to take up smoking.

But the problem with the "exceptions" approach is that there is even less data to inform an approach to helmets. So it may be that if you could get good data it could show, for arguments sake, that wearing a helmet as a 30-35 year old female on a sit up and beg Dutch bike has a safety benefit. But in the absence of that data its not a good idea to assume that you, as a 32 year old female with a Dutch bike, are somehow special and different from the general population. You are much better off assuming that you are just like the general population and there will be no discernible safety benefit. The problem is though that people use "common sense" to impute a benefit but as we know from a number of areas of cycling and safety, common sense is a very unreliable guide.

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Re: why is there not a definative study about helments?

Postby pjclinch » 12 Dec 2014, 9:53am

TonyR wrote:

Which is why it should be a matter of informed personal choice. But based on the overall population statistics you can say its almost certainly not worth wearing one for safety reasons. Of course there are exceptions. Just as the population statistics say you would be foolish to smoke, if you are suffering from a terminal disease with months left to live or you've just reached your 90th birthday then its highly unlikely that taking up smoking is going to kill you but that still does not mean its a good idea for most people to take up smoking.

But the problem with the "exceptions" approach is that there is even less data to inform an approach to helmets. So it may be that if you could get good data it could show, for arguments sake, that wearing a helmet as a 30-35 year old female on a sit up and beg Dutch bike has a safety benefit. But in the absence of that data its not a good idea to assume that you, as a 32 year old female with a Dutch bike, are somehow special and different from the general population. You are much better off assuming that you are just like the general population and there will be no discernible safety benefit. The problem is though that people use "common sense" to impute a benefit but as we know from a number of areas of cycling and safety, common sense is a very unreliable guide.


Population studies show that for folk riding on the general transport network there is no clear and obvious safety benefit from wearing a helmet. It'd be a stretch to extrapolate that to, say, BMX Freecross, because that isn't in the data set (and even if it was the numbers are too small to have much effect). But if you're an avid BMXer you can see how often your comrades are crashing and ending up in hospital, and you can see that it's a lot more than Joe and Jane Utility Cyclist. In which case your more protective gloves, suit, body protection and full-face crash helmet are probably more reliably informed by millennia of putting something between you and a (relatively frequent) whack than what studies said about folk getting from A to B by bike. In other words, someone doing BMX Freecross should assume they're different to the general cycling population, because they are. But they are still "cyclists", and have legitimate reasons for wondering if they should wear a crash helmet.

Having said that, most of us, most of the time, are in the big mixing pot of the general population, and in terms of safety prediction it's as Tony says. Lots of people like to give benefit of the doubt, but T&C apply, and safety changes can go down as well as up... My favourite quick characterisation of the overall effectiveness of helmets for safety is "about zero, plus or minus error bars". Note especially the "or minus"...

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Re: why is there not a definative study about helments?

Postby TonyR » 12 Dec 2014, 2:20pm

pjclinch wrote:Population studies show that for folk riding on the general transport network there is no clear and obvious safety benefit from wearing a helmet. It'd be a stretch to extrapolate that to, say, BMX Freecross, because that isn't in the data set (and even if it was the numbers are too small to have much effect). But if you're an avid BMXer you can see how often your comrades are crashing and ending up in hospital, and you can see that it's a lot more than Joe and Jane Utility Cyclist. In which case your more protective gloves, suit, body protection and full-face crash helmet are probably more reliably informed by millennia of putting something between you and a (relatively frequent) whack than what studies said about folk getting from A to B by bike.


But that illustrates my point perfectly. Its very easy to see that putting something between you and a whack is common sense on the roads too. After all how can an inch or so of cushioning not help when your head hits that car or kerb? But as we know common sense gives the wrong answer because of a whole range of effects - bigger head size, risk compensation, increased rotational effects etc etc. Now in BMX nobody has done the studies AFAIK but why do you think that common sense works there and not on the roads? Certainly the helmets make your head a bigger target in an offie and you can almost guarantee that riders would not try such big stunts without the assumed protection of helmets.

Its very interesting to read a study comparing BMX with ordinary cycles (1) from back in the days when helmets were not the norm where you find:

"The overall proportion of injuries above the neck was 53% in the ordinary group and 31% in the BMX group, a significant difference."


Perhaps not what common sense would have you believe.


Having said that, most of us, most of the time, are in the big mixing pot of the general population, and in terms of safety prediction it's as Tony says. Lots of people like to give benefit of the doubt, but T&C apply, and safety changes can go down as well as up... My favourite quick characterisation of the overall effectiveness of helmets for safety is "about zero, plus or minus error bars". Note especially the "or minus"...


I agree with you there.


(1) BMX compared with ordinary bicycle accidents. C M Illingworth Arch Dis Child 1985;60:5 461-464 doi:10.1136/adc.60.5.461

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Re: why is there not a definative study about helments?

Postby pjclinch » 12 Dec 2014, 2:50pm

TonyR wrote:
pjclinch wrote:Population studies show that for folk riding on the general transport network there is no clear and obvious safety benefit from wearing a helmet. It'd be a stretch to extrapolate that to, say, BMX Freecross, because that isn't in the data set (and even if it was the numbers are too small to have much effect). But if you're an avid BMXer you can see how often your comrades are crashing and ending up in hospital, and you can see that it's a lot more than Joe and Jane Utility Cyclist. In which case your more protective gloves, suit, body protection and full-face crash helmet are probably more reliably informed by millennia of putting something between you and a (relatively frequent) whack than what studies said about folk getting from A to B by bike.


But that illustrates my point perfectly. Its very easy to see that putting something between you and a whack is common sense on the roads too. After all how can an inch or so of cushioning not help when your head hits that car or kerb? But as we know common sense gives the wrong answer because of a whole range of effects - bigger head size, risk compensation, increased rotational effects etc etc. Now in BMX nobody has done the studies AFAIK but why do you think that common sense works there and not on the roads? Certainly the helmets make your head a bigger target in an offie and you can almost guarantee that riders would not try such big stunts without the assumed protection of helmets.

Its very interesting to read a study comparing BMX with ordinary cycles (1) from back in the days when helmets were not the norm where you find:

"The overall proportion of injuries above the neck was 53% in the ordinary group and 31% in the BMX group, a significant difference."


Perhaps not what common sense would have you believe.


You're going too far with what you know. The pop. studies on the roads are a different enough environment to top-end BMX that you can't reasonably tell anything much from them in the other context, so that helmets defy one subset of "common sense" there means pretty much nothing in the other. They might but it's not a safe assumption that they will.

BMX from 1985 means about as much to current high end BMX competition as Nordic ski touring does to Olympic Downhill. This sort of thing...



...is a whole different game, and one in which crashes are very, very common, and the lists of hospital procedures the top riders have gone through suggest they tend to be pretty serious too. Serious enough that waving a study about a much lower risk form of cycling and saying PPE might not be apposite just isn't good enough, because at that risk level PPE is a de-facto standard. Am I 100% sure it should be? No. But with the much higher risk levels the onus is now on you to show a helmet is a bad idea, just as the onus is on the pro helmet lbby to show they're worth it in the much lower risk environment of the streets.

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