Bike helmets and safety: a case study in difficult epidemiology

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Ok, but I refuse to pay for your healthcare since you are assuming so much extra risk. Spend a week in a hospital for treatment of a head injury that was easily preventable with a cheap bicycle helmet? That should all come out of your pocket, not society’s – or mine.

Same argument applies to smoking, really. Do it all you want, just don’t make me pay for the effects of your risky behavior.

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I suggest a bike helmet that looks like a giant head, maybe with fake hair.

Ah, @marktech, you want to play my favorite game on the Internet, My Data Can Beat Up Your Data? Very well then.

There are several meta-analyses and reviews which synthesize and evaluate the results of multiple case-control studies. A Cochrane review of case-control studies of bicycle helmets by Thompson et al. found that “helmets provide a 63 to 88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists. Helmets provide equal levels of protection for crashes involving motor vehicles (69%) and crashes from all other causes (68%). Injuries to the upper and mid facial areas are reduced 65%.”

A 2001 meta-analysis of sixteen studies by Attewell et al. found that, compared to helmeted cyclists, unhelmeted cyclists were 2.4 times more likely to sustain a brain injury; 2.5 times more likely to sustain a head injury; and 3.7 times more likely to sustain a fatal injury.

I guess it’s like smoking data in the 1930s and 1940s – “the jury is still out!”

I think it is fine if people want to cycle without helmets, the risk is certainly lower than, say, motorcycling without a helmet which is borderline suicidal given the vast difference in physics energy and regular exposure to motor vehicles. But when you learn that 62% of bicycle related deaths are head injuries…

Each year, nearly 1,000 persons die from injuries caused by bicycle crashes, and 550,000 persons are treated in emergency departments for injuries related to bicycle riding. Approximately 6% of the bicycle riders treated in emergency departments require hospitalization. Head injuries account for 62% of bicycle-related deaths, for 33% of bicycle-related emergency department visits, and for 67% of bicycle-related hospital admissions.

… It seems awfully dumb not to slap a $20 bicycle helmet on your head to mitigate that risk.

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Well, except that motorists are fully encased in steel crash cages, and wear federally mandated seatbelts when driving. Other than that… totally identical to bicycles.

Because head injuries are some of the worst, most dangerous injuries the body can sustain. Sure, being a fatass might kill you 5 or 10 years early, but slamming your unprotected head into the pavement at 20 miles per hour will kill you in a day, if not instantly.

Besides the massive difference in risk, It’s also a lot easier and cheaper to say “place this $20 helmet on your head, please” than “change your whole lifestyle”.

Still, only 1,000 US cycling deaths per year isn’t many. Maybe it just doesn’t matter?

Each year, nearly 1,000 persons die from injuries caused by bicycle crashes, and 550,000 persons are treated in emergency departments for injuries related to bicycle riding. Approximately 6% of the bicycle riders treated in emergency departments require hospitalization. Head injuries account for 62% of bicycle-related deaths, for 33% of bicycle-related emergency department visits, and for 67% of bicycle-related hospital admissions.

For comparison, Wikipedia says in the USA there are ~4,500 motorcycle deaths per year, and ~35,000 automobile deaths. So 1,000 bicycle deaths, ~620 of which are head injury related… I’d still say wear a cheap bicycle helmet, unless you for some reason enjoy taking unnecessary, pointless risks.

Why would I be interested in population life expectancy?

It’s a specious comparison. Where does it say that the purpose of cycling is to increase population life expectancy versus … provide them basic transportation?

I have a basic expectation that cars won’t needlessly kill the people inside them when they make common mistakes. I expect the same from bicycles. If you (or someone around you) make a mistake, a $20 bike helmet is going to make it far more likely that you don’t die, just like seatbelts and steel safety cages in automobiles do. The devices we use for transportation should have functional basic safety mechanisms. That is their purpose. (that said I will readily concede 1,000 bicycle deaths per year is not very many and maybe it just doesn’t matter at all in the big scheme of things.)

Do people drive more dangerously in large SUVs where they perceive themselves to be “safer”? Do other motorists drive more aggressively around large automobiles because they look “safer”? This strikes me as extraordinarily difficult stuff to measure through science, and more of an anecdotal excuse to have a particular opinion.

Which is fine, except when “we just don’t know!” is used as ammunition for removing safety mechanisms from basic transportation.

“We just don’t know!” so… make things more dangerous, just because?

I mean, for a while “we just didn’t know” if there was a connection between autism and vaccinations, right, so… cancel vaccinations just in case?

I read the summary in the BB post.

After looking at the absolute number of deaths – 122 cyclists were killed last year in the UK compared to ~1,000 in the US. I am not sure the statistics even matter based on such a small sample size of deaths.

What else killed ~1,000 people in the USA in a year? Let’s see:

  • 1,740 people died from Drug Use
  • 1,606 people died from Epilepsy
  • 691 people died from Hepatatis B
  • 687 people died from Menengitis

(I am sure the UK causes are even more obscure for 122 yearly deaths.)

So mandatory helmet laws, if the statistics I quoted earlier from the CDC are to be believed, would at most potentially save the 62% of those people whose deaths were due to cycling related head injuries – 620 in the US and 75 in the UK.

Given that there are ~380,000 deaths per year from coronary heart disease, I can see why they want to focus on these hand-wavy, nebulous “not wearing a helmet might make more people ride bikes and get slightly less heart disease” ideas. Because the absolute number of yearly cycling deaths is just so impossibly tiny relative to almost every other type of death.

Wear a bicycle helmet, don’t wear a bicycle helmet – statistically speaking, it just doesn’t matter.

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It does seem like the death rate from ‘random accidents’ is much higher than cycling deaths:

For 2010:

  • unintentional falls: 26,009
  • unintentional poisoning: 33,041

This source has similar data for year 2000:

  • pedestrians: 5,870
  • water transport: 630
  • falls: 13,322
  • firearms discharge: 776
  • accidental drowning: 3,482
  • electricity: 296+99 = 395

etc.

Per these stats there are around 200 cycling deaths in the Netherlands per year. Compare with ~122 in the UK and ~1000 in the US.

As I posted above with citations (click my avatar on the left to filter this topic for my posts) these numbers are far lower than the general number of random accident related deaths and many other obscure diseases and afflictions.

As pointed out earlier, cars have steel crash cages and federally mandated seatbelts. Airbags too. Do bicycles have any of that?

Man, you ninjas really ought to bone up on your science skills.

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Well, let’s think. Put on your ninja hat and let’s think… about science!

  • are there more people driving cars or bicycles?
  • do bicycles go faster or slower than cars?
  • are we talking about basic built-in safety features of vehicles, or additional safety features that have to be added at additional expense and effort?

Isn’t this all irrelevant for you? As a ninja, can’t you just run super fast to go places?

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Gee, I wonder why that happens?

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