Evaluating the impact of cycle helmet use...

For all discussions about this "lively" subject. All topics that are substantially about helmet usage will be moved here.
Stevek76
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Re: Evaluating the impact of cycle helmet use...

Post by Stevek76 »

[XAP]Bob wrote: 27 Jun 2021, 12:39pm and no account is made of rotational behaviour (unlike specifications for motorcycle helmets).
Quite a few helmets around that are designed to reduce rotational forces, of course the standard certifications do not bother with such measurements and there are only a couple of independent testers covering a small sample of the market who actually publish detailed numbers.
There are only ~4000 cyclists seriously injured each year, and not all of those will be head injuries (I'd say a broken leg is serious for example).
As far as the recording guidance goes, any broken bone (or suspected break) is supposed to be recorded as serious though it's generally considered that a number of serious are misreported as slight and a large number of slights aren't recorded at all (potentially up to twice the number that are)

On the flip side, as far as judging transport risks goes, the collision stats will include and be biased by sportsing road cyclists who, at least in my anecdotal impressions, appear to be the group a great many of the 'my helmet saved my life' advocates belong to and generally appear to crash more. That's a very different risk profile to someone cycling to the shops.

This also shows if you use the cycling distance estimates from the LTDS with the casualty figures from the greater London area, the fatality rates are significantly lower than the national average, despite the ability of London news of cyclists being crushed by HGVs being better able to make national significance.
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drossall
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Re: Evaluating the impact of cycle helmet use...

Post by drossall »

[XAP]Bob wrote: 27 Jun 2021, 12:39pmI know people who have smashed their entire face in whilst wearing a lid (and they would likely have been much less badly injured if they hadn't been, since it wouldn't have twisted their face into the corner of the car by catching on the roof rail).
My second crash to involve significant head impact resulted in quite a severe scalp injury just below the helmet line , and a badly-dazed cyclist. My wife, collecting me from the hospital, remarked that, had I been wearing a helmet, an impact there might have produced quite a bad neck injury because of the additional twisting from the larger head (and my head is big enough already - see other discussions on finding helmets to fit).

This is all speculative, of course, because there's no way to tell without reproducing the accident with and without lid - so I've no idea whether her common-sense is right or not. But she's a non-cyclist with no vested interest other than not having to fetch me from hospital again too often.

But I escaped with stitches and no concussion. And I am certain that, had the outcome with a helmet been no different, I would have been told quite firmly how it had saved me. So science is the only way I can see to know whether or not there would in fact have been any difference.

Incidentally, an old-style hairnet might potentially have been the best compromise. But of course no-one thinks them worth testing.
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[XAP]Bob
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Re: Evaluating the impact of cycle helmet use...

Post by [XAP]Bob »

Stevek76 wrote: 27 Jun 2021, 2:12pm
[XAP]Bob wrote: 27 Jun 2021, 12:39pm and no account is made of rotational behaviour (unlike specifications for motorcycle helmets).
Quite a few helmets around that are designed to reduce rotational forces, of course the standard certifications do not bother with such measurements and there are only a couple of independent testers covering a small sample of the market who actually publish detailed numbers.
I was specifically referring to the specifications of lids - I am aware that there are a handful of lids which are supposed to be rotationally tested, but against what standard it's hard to say (and the number of them is still pretty small AFAIK).
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drossall
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Re: Evaluating the impact of cycle helmet use...

Post by drossall »

The rotational issue has been curious. It was one cause raised as a possible explanation for statistics that questioned whether helmet-wearing was bringing the expected benefits. The response was exactly the same as now, that helmets were obviously necessary. Now, rotational testing is promoted as a safety feature. But if it's necessary, and helmets without it are not so safe, the previous advocacy for them must have been less well-founded. There doesn't seem to have been any recognition of that?
Jdsk
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Re: Evaluating the impact of cycle helmet use...

Post by Jdsk »

Jdsk wrote: 27 Jun 2021, 9:37am It's perfectly possible to have an evidence-based discussion of the many different issues and what's known and what isn't known.

But unfortunately that hasn't been what's happened in the past in this forum.

It's up to us whether that's what happens in the future in this forum.
Maybe next time?

Jonathan
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Re: Evaluating the impact of cycle helmet use...

Post by Steady rider »

Curnow provides a good view of the issues involved.
https://www.cyclehelmets.org/papers/p787.pdf
page 158 mentions,
Worse, in some circumstances wearing a helmet can increase the angular acceleration which an oblique impulse imparts to the head, increasing the risk of damage to the brain, especially diffuse axonal injury
.
https://trid.trb.org/view/810710
Assuming that the response of the unhelmeted head is similar to the helmeted head during an oblique impact at 8.5m/s at 15o, this may generate between 7500rad/s² and 12000rad/s² of rotational acceleration. This is potentially more severe than the 3000rad/s² to 8500rad/s² measured during abrasive and projection oblique tests with size 54cm (E) helmeted headforms. However, for the most severe cases using a size 57cm (J) headform, rotational acceleration was typically greater than 10,000rad/s² and increased to levels of 20,000rad/s², a level at which a 35% - 50% risk of serious AIS3+ injuries is anticipated. Overall, it was concluded that for the majority of cases considered, the helmet can provide life saving protection during typical linear impacts and, in addition, the typical level of rotational acceleration observed using a helmeted headform would generally be no more injurious than expected for a bare human head. However, in both low speed linear impacts and the most severe oblique cases, linear and rotational accelerations may increase to levels corresponding to injury severities as high as AIS 2 or 3, at which a marginal increase (up to 1 AIS interval) in injury outcome may be expected for a helmeted head.
The true response of the bare human head to oblique, glancing blows is not known and these observations could not be concluded with certainty, but may be indicative of possible trends.
Australia introduced the laws knowing rotational aspects were significant and were not included in standards and knowing they would likely discourage cycling. They provided information supporting the laws without explaining fully the negative consequences.
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pjclinch
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Re: Evaluating the impact of cycle helmet use...

Post by pjclinch »

Steady rider wrote: 30 Jun 2021, 8:18pm
Australia introduced the laws knowing rotational aspects were significant and were not included in standards and knowing they would likely discourage cycling. They provided information supporting the laws without explaining fully the negative consequences.
For some values of "knowing"...

Laws are introduced by parliaments, not nations, and while members have the opportunity to get informed that's no guarantee they will, or have the capacity to understand the information if they do, or won't be swayed by counter-information. "Australia" isn't a simple entity making a simple decision.

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Pete Owens
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Re: Evaluating the impact of cycle helmet use...

Post by Pete Owens »

it has the usual failure of this type of study as it excludes the vast majority of riders who don't end up in hospital. If you don't measure the propensity for helmeted and unhelmeted cyclists to end up hospitalised in the first place then detailed analysis of a highly selective subset tells you diddly squat.

The only statistc that could compare whether there is any merit in wearing helmets is:

mean distance travelled per death
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NATURAL ANKLING
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Re: Evaluating the impact of cycle helmet use...

Post by NATURAL ANKLING »

Hi,
Pete Owens wrote: 3 Aug 2021, 1:00pm it has the usual failure of this type of study as it excludes the vast majority of riders who don't end up in hospital. If you don't measure the propensity for helmeted and unhelmeted cyclists to end up hospitalised in the first place then detailed analysis of a highly selective subset tells you diddly squat.

The only statistc that could compare whether there is any merit in wearing helmets is:

mean distance travelled per death
in over 50 years of cycling and probably 30 years wearing a helmet, I've broken two in the last two years, no other damage to any helmets.
The first time I went to the hospital but a week later on, And head symptoms had already gone I said I Fell off my bike but I was not asked if I was wearing a helmet.
Both times I had mild concussion.
So I'm not included in any statistics at all.
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Mike Sales
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Re: Evaluating the impact of cycle helmet use...

Post by Mike Sales »

NATURAL ANKLING wrote: 3 Aug 2021, 1:29pm
So I'm not included in any statistics at all.
There are always cases missed in the data.
What has to be avoided is systematic bias.
It's the same the whole world over
It's the poor what gets the blame
It's the rich what gets the pleasure
Isn't it a blooming shame?
mattheus
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Re: Evaluating the impact of cycle helmet use...

Post by mattheus »

NATURAL ANKLING wrote: 3 Aug 2021, 1:29pm Hi,
Pete Owens wrote: 3 Aug 2021, 1:00pm it has the usual failure of this type of study as it excludes the vast majority of riders who don't end up in hospital. If you don't measure the propensity for helmeted and unhelmeted cyclists to end up hospitalised in the first place then detailed analysis of a highly selective subset tells you diddly squat.

The only statistc that could compare whether there is any merit in wearing helmets is:

mean distance travelled per death
in over 50 years of cycling and probably 30 years wearing a helmet, I've broken two in the last two years, no other damage to any helmets.
The first time I went to the hospital but a week later on, And head symptoms had already gone I said I Fell off my bike but I was not asked if I was wearing a helmet.
Both times I had mild concussion.
So I'm not included in any statistics at all.
If you reported to a hospital and got looked at, you're in their statistics.

If they concluded mild concussion, I would expect you to be recorded (as some variation on head/brain injury) in some statistics, somewhere in their system.
Jdsk
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Re: Evaluating the impact of cycle helmet use...

Post by Jdsk »

mattheus wrote: 3 Aug 2021, 2:07pmIf you reported to a hospital and got looked at, you're in their statistics.
"Hospital Episode Statistics" in England:
https://digital.nhs.uk/data-and-informa ... statistics
https://digital.nhs.uk/data-and-informa ... dictionary

Jonathan
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NATURAL ANKLING
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Re: Evaluating the impact of cycle helmet use...

Post by NATURAL ANKLING »

Hi,
Concussion after a week had subsided so I did not mention at all.
My reason for hospital was after a week I could not bear weight on my left leg, so I was reported as a cycling accident but that's all, helmet was not mentioned.
My second helmet damage I did not seek hospital or any other help.
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mattheus
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Re: Evaluating the impact of cycle helmet use...

Post by mattheus »

NATURAL ANKLING wrote: 3 Aug 2021, 2:16pm Concussion after a week had subsided so I did not mention at all.
My reason for hospital was after a week I could not bear weight on my left leg, so I was reported as a cycling accident but that's all, helmet was not mentioned.
I don't know what point you're trying to make here, but clearly if you wait until some of your symptoms clear-up before going to hospital, that is going to skew your tiny contribution to the statistics.
Not really a surprise, is it?!?


In general, if you have a nasty head injury - irrespective of other less glamorous ailments - you are likely to go to A&E/minor-injuries, or be taken there by some kind person. On average I would say that a bleeding head-wound will get more immediate attention than minor twinges to limbs and the like (concussion being Serious Business that needs assessing ASAP, and of course the blood that tends to gush from even quite minor head wounds, in an attention-grabbing way. As I could recently testify to ...)
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Re: Evaluating the impact of cycle helmet use...

Post by Pete Owens »

The problem is the systematic failure to include any statistics whatsoever from the 99.9999% of cycle trips that do not involve a trip to a hospital means that the study tells you nothing whatsoever about whether helmets make cycling safer or more dangerous.
Every single case in the sudy is one where a cyclist has failed to be protected from serious injury yet we don't know whether helmet wearers are over or under represented in the study. I
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