Re: Helmet efficacy test

On Wed, 26 Mar 2025 11:47:24 -0400, Frank Krygowski
<frkrygow@sbcglobal.net> wrote:

On 3/26/2025 10:16 AM, Zen Cycle wrote:

On 3/25/2025 10:24 PM, Frank Krygowski wrote:

On 3/25/2025 5:02 PM, cyclintom wrote:

>
How would you propose that a helmet cause a head injury? You could
argue that the foam helmets are heavy and might increase your chances
of hitting your head but the Wavecel helmets are light. Helmets don't
interfere with vision on a normal road bike.

>
There's data out there indicating that people wearing helmets do crash
more (and show up in ER more) than people without helmets.

 
Irrelevant, even if it were true. Statistical analysis on injuries with
vs sans helmets take that into account.

>
Nope. Here's why:
>
The typical "case-control" study design - that is, counting head
injuries (usually) or brain injuries in those presenting to ER, is built
on the assumption that the sample presenting to ER is representative of
the cylcling population as a whole. There's a significant amount of data
showing that's not the case. Specifically, people wearing helmets
present to ER more than the general cycling population.
>
The easiest example to find is the 1989 Thompson & Rivara paper. That
team of doctors was all in on helmet promotion before they published
their "case-control" study claiming 85% protection. They had just
completed street surveys of the study area that found ~3% of cyclists
were wearing helmets. But the cyclists presenting to ER had 21% wearing
helmets. IOW, a person wearing a helmet was seven times more likely to
show up in ER.
>
Why would that be? There are various possibilities. One might be that
the most nervous people would be the first to cave in to helmet fear
mongering, and when they felt a head bump they thought "Omigosh, I might
die!" and went to ER just to be sure. Another might be that helmeted
people might suffer more head (or really, helmet) strikes with the
ground just because the helmet is bigger than the head. (Evolution, like
of reflexes and neck muscles, etc. tends to be efficient, i.e. nothing
extra.) It might be that the people in helmets had better insurance
coverage and didn't fear ER expense.
>
There were other differences between the "cases" and "controls," as well
as between both groups and the general population - as explained here:
https://www.cyclehelmets.org/1131.html  and that is generally the case.
Another study by a Dr. Crocker of Austin, TX was performed specifically
to promote the idea of an all-ages mandatory helmet law (MHL). Crocker's
study failed to find significant benefit from helmets, largely because
he included a confounding factor almost always missed: Alchohol
consumption. He found that drinking then riding significantly increased
risk of brain injury, but riding sober without a helmet did not have
significantly more risk than riding with a helmet. This is important,
because (almost?) all other pro-helmet studies have not recorded blood
alcohol content, and there's no way to retroactively know which of the
injured no-helmet folks were tipsy.
>
>

 
(No, it's not

because those without helmets didn't survive, as some have claimed.)
>
While not a direct mechanical cause if injuries, some studies - and
many, many posted discussion remarks - indicate that people wearing
helmets are indulging in "risk compensation" meaning "Hey, I'm wearing
a helmet do I can take more risks." (I did that today, but I'll
probably wait until tomorrow to post about it.) We've had people post
here that they would never do the risky mountain biking they do
without the helmet. We've had people say "I would never ride that busy
road without a helmet."
>
Risk compensation is probably near-universal with lots of "safety"
devices. It's not inappropriate as long as the increase in risk is
commesurate with the increase in protection.

 
Again irrelevant. The Moral Hazard argument has a place, but it isn't in
the discussion of whether helmets are protective or not.

>
If you're restricting discussion to mechanical effectiveness, you're
correct. If you're allowing discussion on overall reduction in brain
injury due to widespread helmet use, you're wrong. If a person takes
additional risks because of overestimating his invulnerability, he's
likely to pay for the indiscretion. And almost all helmet promotion is
intended to trigger widespread use in hopes of reducing total injury
rates or counts.
>

Trouble is, the protection from a bike helmet is far, far less than
people are led to believe. Look up the standardization test.

 
"led to believe" by what metric? I've never seen any literature claiming
a helmet _prevents_ serious head trauma.

>
WHAT???
>

Oh, and about helmets mechanically causing injury? Curiosity about
that surged once it became clear that helmeted cyclists seemed to be
over represented in concussion counts.
>
Well, since the helmet certification standard was established
(essentially less than 300gs linear deceleration in a 14 mph impact),
it became known that linear deceleration was far less of a problem
than rotational acceleration. Twisting the head and brain caused far
more brain injury than smacking them. But a helmet protrudes at least
an inch from the head, providing a longer lever arm for glancing
blows, potentially worsening rotational acceleration. (Note that a
bare head's slippery hair and very loose scalp are probably
evolutionary tricks to reduce that hazard. The helmet makes those
ineffective.)

 
a specious argument with no scientific substantiation.

>
What part did you not understand?

"The easiest example to find is the 1989 Thompson & Rivara paper. That
team of doctors was all in on helmet promotion before they published
their "case-control" study claiming 85% protection. They had just
completed street surveys of the study area that found ~3% of cyclists
were wearing helmets. But the cyclists presenting to ER had 21%
wearing helmets. IOW, a person wearing a helmet was seven times more
likely to show up in ER."

<EYEROLL> A study with no real numbers?  How big was the sample?  25
or 2500? What percentage of the riders were racers who were lilkely to
be wearing helmets and more likely to have accidents? How many who
went to the ER had head injuries? How many had scrapes and bruises on
other parts of their bodies?

Some people will believe any "study" that supports their agenda,
without examining the data.

--
C'est bon
Soloman