Comment by peoplefromibiza | Hacker News Reader

Comment by peoplefromibiza | Hacker News Reader

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peoplefromibiza

> Not really? There may be slight reductions in some injuries as a result of helmet use,

Yes, actually, really!

Helmets provide a 63 to 88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7025438/

There was a significantly higher crude 30-day mortality in un-helmeted cyclists 5.6% (4.8%–6.6%) versus helmeted cyclists 1.8% (1.4%–2.2%) (p<0.001). Cycle helmet use was also associated with a reduction in severe traumatic brain injury (TBI) 19.1% (780, 18.0%–20.4%) versus 47.6% (1211, 45.6%–49.5%) (p<0.001), intensive care unit requirement 19.6% (797, 18.4%–20.8%) versus 27.1% (691, 25.4%–28.9%) (p<0.001) and neurosurgical intervention 2.5% (103, 2.1%–3.1%) versus 8.5% (217, 7.5%–9.7%) (p<0.001).

https://bmjopen.bmj.com/content/9/9/e027845

“The evidence is clear: helmets save lives and significantly reduce the risks of severe injury,” said Lois K. Lee, MD, MPH, FAAP, lead author of the statement, written by the AAP Council on Injury, Violence, and Poison Prevention. “And yet sports-related injuries make up a substantial proportion of all traumatic brain injuries. As a pediatric emergency medicine physician, I advise all my patients – and their parents-- to wear helmets.”

https://www.aap.org/en/news-room/news-releases/aap/2022/amer...

I don't think I'm necessarily disagreeing that in the worst-case scenario that helmets do the job of reducing brain and skull trauma. Doing something is the alternative to doing nothing, you'd expect some difference here.

My problem is that helmet use isn't exactly "well-studied." All these studies look at existing reports from medical centres on injuries & deaths. This doesn't actually account for the broader behavioural changes in the system, or look at causes outside of "injured while wearing a helmet vs. not."

In any other industry this kind of reporting (while factual) is absolutely ignoring everything else. A short list of what isn't being considered:

- Which road and behaviour led to incident?

- Which kinds of road conflicts can be addressed by helmets?

- How did road design lead to the incident?

- Were environmental factors a concern (winter, ice, rain, etc.)?

- How does behaviour for the cyclist change as a result of not wearing a helmet?

- How does behaviour for other road users change as a result of a cyclist not wearing a helmet?

- What kinds of helmets are more viable for protection in the case of the most extreme (and most common) conflict scenarios? How do we then test these helmets to ensure compliance in manufacturing?

These are all questions you'd expect to be answered here, and then you'd do the cost-benefit analysis on whether a mandate is necessary or not. A "well-studied" field would have discussed these effects in broader detail, not just short-cut to "fewer people who already had huge injuries while cycling died when using a helmet." That is not the entire problem, because it leaves out a huge sampling of people who do not wear helmets and do not make it to the hospital in the first place.

The kicker is rate of head injuries during a bicycle crash. A fraction of crashes involve a person's head (though when it does, for those one in ten falls, you really want it)

The numbers are under reported. Every cyclist I know that uses a bike for transport has been hit by a car. Myself thrice, never reported. Crashes involving myself, never reported. Hence, there is a bias in the data for the really traumatic injuries

There's some debunking of helmet studies here: https://www.cyclehelmets.org/1027.html

thanks.

A very good example of what "selection bias" means.

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