The CycleChat Helmet Debate Thread

[doog]

In the BBC link it said "The helmet definitely saved me,"..nothing about saving his life.

 

[Big Andy]

For the umpteenth plus one time, there is no such thing.

What makes you say that?
http://www.dictionary.com/browse/anecdotal-evidence

Anecdotal proof doesnt exist I would suggest. Anecdotal evidence most definitely does. Shouldnt carry the same weight as scientific evidence but shouldn't be dismissed out of hand.

 

[Mugshot]

I introduced the Deer story as its topical, the guy had an accident, he landed on his head, he was wearing a helmet, he said it helped him, he got up and carried on riding. The fact that a Deer hit him was immaterial, it is all about the helmet story and the excellent photo that goes with the story.
I'm amazed it bothers you so much how some accidents occur, only the "correct" type of accident is allowed in this thread is it? Just like the "correct" type of damage on a helmet after an accident when wearing one..........

The deer is immaterial? Considering it was the deer that knocked him off I would say it's very far from immaterial, nor is the fact that the chances of that happening are more than vanishingly remote. As for the frankly ludicrous hyperthetical scenario we had to endure earlier, well maybe the less said the better. My interest in how incidents occur is rather relevant if you take the time to give that some thought.

 

[Justinslow]

For the umpteenth plus one time, there is no such thing.

I'm sure in the "rules" of this thread "anecdotal evidence" is fine?

Anyway for all those having trouble with the Deer story here's a little reminder of the definition of the word "accident" you know, the things we sometimes have on bikes.

 

[Big Andy]

The deer is immaterial? Considering it was the deer that knocked him off I would say it's very far from immaterial, nor is the fact that the chances of that happening are more than vanishingly remote. As for the frankly ludicrous hyperthetical scenario we had to endure earlier, well maybe the less said the better. My interest in how incidents occur is rather relevant if you take the time to give that some thought.

How incidents occur is of course very relevent, however if you accept that incidents/accidents will always occur no matter what preventative measures you take surely you are then in a position where you have to decide what steps you consider are appropriate, if anything, to mitigate the effects of the incident. Assuming yof course you consider the chances of an incident/accident are great enough to warrant it.

 

[doog]

for the umpteenth time he didnt say it definitely saved his life

 

[swansonj]

For the umpteenth plus one time, there is no such thing.

How would you classify the "case report", as carried by most reputable medical journals? Essentially anecdotal, but still carrying some evidential value?

 

[Mugshot]

How incidents occur is of course very relevent, however if you accept that incidents/accidents will always occur no matter what preventative measures you take surely you are then in a position where you have to decide what steps you consider are appropriate, if anything, to mitigate the effects of the incident. Assuming yof course you consider the chances of an incident/accident are great enough to warrant it.

Which is in many respects the crux of the issue. To me, and it would appear the stats back this up, cycling is extraordinarily safe and is in no way dangerous enough, in most of its disciplines, to merit the wearing of specific protective equipment. Yet through a concerted effort by manufacturers and governing bodies we have a huge number of cyclists and non cyclists that are convinced that to not wear a helmet is beyond foolish. Evidence is dismissed in favour of anecdote and sensible discussions are marred by the introduction of examples such as rogue deer (which as I suspected was not tongue in cheek). Whilst they are frequently dismissed I personally think that the comparisons to other everyday activities are valid, I struggle to see the distinction between one statistically very safe activity which allegedly needs protective equipment and another statistically very safe activity which apparently does not.

 

[srw]

How would you classify the "case report", as carried by most reputable medical journals? Essentially anecdotal, but still carrying some evidential value?

I'd say that they're a bit more scientific than your typical Bransonesque "my helmet definitely saved my life" claim.

On this sort of subject wikipedia tends to be reliable, so I'll use it as my source.
https://en.wikipedia.org/wiki/Case_report

From that, here are some examples of things that good case reports have that most "anecdotal evidence" we see on this forum and in the news don't have.

In medicine, a case report is a detailed report of the symptoms, signs, diagnosis, treatment, and follow-up of an individual patient. Case reports may contain a demographic profile of the patient, but usually describe an unusual or novel occurrence. Some case reports also contain a literature review of other reported cases.

Detail, symptoms, diagnosis, treatment, follow-up, unusual or novel? No.

Most case reports are on one of six topics:[1]

• An unexpected association between diseases or symptoms.
• An unexpected event in the course of observing or treating a patient.
• Findings that shed new light on the possible pathogenesis of a disease or an adverse effect.
• Unique or rare features of a disease.
• Unique therapeutic approaches.
• A positional or quantitative variation of the anatomical structures.

Unexpected association? No
Unexpected event? No
New findings? No
Unique or rare features? No
Unique therapeutic approaches? No
Variation of anatomical structures? No

Given their intrinsic methodological limitations, including lack of statistical sampling, case reports are placed at the foot of the hierarchy of clinical evidence, together with case series.[3]

At the foot of the hierarchy of evidence? No. Usually held up as the gold standard.

I could go on, but it's not really worth it, is it?

Case reports are of novel and unusual events, or of novel and unusual treatments, and will, where the subject is open to the approach, lead to proper statistical analysis to confirm or reject the anecdote.

We are dealing with a subject which is easily open to statistical analysis and where there is no novelty in the reports, which are sensational and not scientific.

I think @User is right - in this context there is no such thing as anecdotal evidence. What's really frustrating is that there are dozens of statistical analyses which could be done with data which is either already available or which could be collected very easily and cheaply.

[edited to tidy up quote cock-ups]

 

[doog]

Which is in many respects the crux of the issue. To me, and it would appear the stats back this up, cycling is extraordinarily safe and is in no way dangerous enough, in most of its disciplines, to merit the wearing of specific protective equipment. Yet through a concerted effort by manufacturers and governing bodies we have a huge number of cyclists and non cyclists that are convinced that to not wear a helmet is beyond foolish. Evidence is dismissed in favour of anecdote and sensible discussions are marred by the introduction of examples such as rogue deer (which as I suspected was not tongue in cheek). Whilst they are frequently dismissed I personally think that the comparisons to other everyday activities are valid, I struggle to see the distinction between one statistically very safe activity which allegedly needs protective equipment and another statistically very safe activity which apparently does not.

Now that's a post lifted from the non helmet wearing classic book of quotes.

However in the history of this forum every single piece of first hand evidence from people who have actually fallen onto their heads whilst wearing a lid has been dismissed out of hand..even the introduction of someone falling on their head having been struck by a deer has been dismissed out of hand.

Explain that.

 

[srw]

Now that's a post lifted from the non helmet wearing classic book of quotes.

However in the history of this forum every single piece of first hand evidence from people who have actually fallen onto their heads whilst wearing a lid has been dismissed out of hand..even the introduction of someone falling on their head having been struck by a deer has been dismissed out of hand.

Explain that.

Perhaps you'd like to read the post I made a minute before yours....

(And it's not "dismissing out of hand", it's "recognising the evidential limitations of". As you probably know by now, if you understand the concept of evidence.)

 

[srw]

I dealt with proving evidence beyond reasonable doubt for 30 years...you deal in the balance of probabilities ...

I think I understand the concept of evidence..thankyou.

I don't think you do. Or what "the balance of probabilities" actually means.....


I assume you were a cop or a lawyer? Neither profession exactly known for their ability to deal with population statistics.

 

[doog]

I don't think you do. Or what "the balance of probabilities" actually means.....

I assume you were a cop or a lawyer? Neither profession exactly known for their ability to deal with population statistics.

You were questioning if I understood the concept of evidence - yes I do. How far do you want to take it ?

You've previously said you work for an Insurance company - who work on the balance of probabilities.

I never introduced the below the belt accusation about understanding the concept of evidence - you did.

 

[srw]

You were questioning if I understood the concept of evidence - yes I do..

Good. Delighted to hear it.

Now perhaps you'll address the substance? It is my assertion that in the context of trying to understand what kinds of personal protection are useful for cycling anecdotal, individual evidence is very weak, and statistical evidence is considerably stronger. The case study is interesting but not conclusive - only a properly designed population study can be conclusive.

Now, which bit of that do you disagree with, and why?

 

[doog]

Good. Delighted to hear it.

Now perhaps you'll address the substance? It is my assertion that in the context of trying to understand what kinds of personal protection are useful for cycling anecdotal, individual evidence is very weak, and statistical evidence is considerably stronger. The case study is interesting but not conclusive - only a properly designed population study can be conclusive.

Now, which bit of that do you disagree with, and why?

The statistical evidence you rely on is incomplete and flawed. It's something I have said on here since the year dot.