Forest plot of odds ratios (95% CI) of helmet use and serious and fatal head injury from individual studies and multivariate meta-regression. H, helmet; NH, no helmet.
Forest plot of odds ratios (95% CI) of helmet use and serious and fatal head injury from individual studies and multivariate meta-regression. H, helmet; NH, no helmet (source: Olivier and Creighton)

A new study of the effectiveness of bicycle helmets in mitigating injury confirms what we’ve known for a long time: bicycle helmets really do work (see Bike helmet review throws cold water on sceptics: they’ll likely save your life).

Jake Olivier and Prudence Creighton from the School of Mathematics and Statistics, UNSW, have just published a review of the literature on this topic in the International Journal of Epidemiology, Bicycle injuries and helmet use: a systematic review and meta-analysis. They reviewed 40 studies that collectively examined 64,000 injured cyclists in eleven countries and concluded that:

Helmet use is associated with odds reductions of 51% for head injury, 69% for serious head injury, 33% for face injury and 65% for fatal head injury. Injuries to the neck were rare and not associated with helmet use.

The authors emphasise that the “reductions were greater for serious injury” and “neck and diffuse axonal injury were rare among cyclists and were not associated with helmet use.

As I’ve noted before (e.g. see here and here), the weight of evidence indicates bicycle helmets do the intuitively obvious; they mitigate head injuries, especially serious ones. While they’re not a silver bullet, they provide big private and social benefits. But there are some important caveats:

  • Wearing a bicycle helmet is only one part of the safety equation for cyclists – good infrastructure and effective regulation of motorists is very likely much more important.
  • Cycling on roads is not as safe as taking public transport or driving, but by the same token the risks aren’t so high they outweigh the benefits of riding e.g. see here, here, here and here.
  • Helmets are beneficial for all riders but their usefulness varies e.g. riders of road bikes are much more likely on average to crash than riders of upright bikes.
  • Just because helmets are effective doesn’t automatically mean helmets should be mandatory; there are plenty of things with a high social and personal cost that we nevertheless choose for various reasons to leave to individual choice.

Unfortunately, the compelling logic of wearing a helmet is consistently questioned by some opponents of Australia’s mandatory helmet law who’re prepared to assert helmets aren’t effective in reducing injury; some even argue they increase the risk of some types of injury.

Their justification is that the helmet law significantly reduces the level of cycling. But even if that’s true, demonising helmets is nevertheless morally unsupportable. It’s unethical to actively mislead cyclists – or to deny them accurate information – about the protective benefit of wearing a helmet.

Australia’s mandatory helmet law is a vexed issue, but it should be debated on the substantive issues e.g. whether or not, relative to the benefits, it reduces cycling participation significantly; or is an unreasonable constraint on individual choice.

The evidence shows it’s a good idea to wear a helmet in most situations, especially when cycling on Australian roads. It’s time to call bullshit on those who assert they’re worse than useless.