Cycling is dangerous, and should be banned unless participants wear helmets. That at least is the message an independent observer would take from reading that – a few weeks ago – the Advertising Standards Authority (ASA) banned an advert from Cycling Scotland. This seems to make sense, doesn’t it? People who ride bicycles without wearing a helmet get brain damage.

It stands to reason that banning cycling without protective clothing is a good thing, doesn’t it? Just as it stands to reason that aspirin is good for viral fevers and that an anti-emetic is good for treating morning sickness. There haven’t been any clinical trials, but the ASA, the Highway Code and many people I know all hold that cycling without a helmet should be a criminal offence. The evidence that a 20 quid piece of plastic and foam can save your life must be incredibly compelling.

Some jurisdictions have taken the step of banning cycling without a helmet. In Australia for example, it is now illegal even for children to ride around without a helmet. And in Australia, cycling-related deaths have fallen. But what’s intriguing is that cycling overall has also fallen, at a faster rate than cycling-related fatalities. In other words, the rate of cyclist death has increased. More worryingly, the rate of head injuries – which one might naively expect to be more directly affected by helmet use – has not fallen as a result of legislation, again implying that the rate has gone up. (See the links here.) Put another way, if you cycle in Australia, where cycle helmets are mandatory, you’re more likely to get a head injury now than before the law was changed.

I’m not telling you anything new. Goldacre and Spiegelhalter, among others, have already come to the conclusion that cycle helmet legislation has at best a minimal effect on reducing head injuries in cyclists. Undue promotion of helmet use (to step away, for a moment, from the inflammatory “banning cycling without helmets”-kind of language) propagates the myth that cycling is dangerous and that you’re stupid or some kind of dangerous rebel if you don’t wear a helmet. (In fact, the rate of head injuries among motor vehicle occupants, cyclists and pedestrians admitted to hospital is remarkably similar – and you get very few people calling for pedestrians to be made to wear helmets.) It’s probably only a matter of time before someone gets their children taken away from them because they don’t make them wear cycle helmets – while riding a scooter, most likely.



But all right then, surely some protection is better than no protection? A 20 quid piece of plastic and foam might not help you at all if you’re trapped between the wheels of a 40 ton artic and the tarmac, but it should have some effect in less drastic situations, yes?

Maybe.

There’s actually precious little good evidence, and certainly nothing of the level that would persuade a regulatory authority such as the European Medicines Agency to approve an intervention of this kind. Most of the studies done on helmet effectiveness tend to be of the case-control variety, where people presenting with a head injury are assumed to be representative of the population at large. Conclusions drawn from such studies are at major risk of confounders and bias, not the least of which is the assumption that helmeted and non-helmeted riders have an equal accident rate (and that the paramedics on the scene actually check the box that refers to whether a not a helmet was worn). Road traffic accident statistics do not record whether or not a helmet was worn, and neither do they distinguish between a scratch to the face and a serious head injury.

There is on the other hand some evidence that wearing a helmet can increase the likelihood of having a head injury: this could be because helmeted riders might be less experienced, because they engage in pursuits that are reasonably dangerous (such as off-roading), because they cycle faster, because they’re Dutch, or because of risk compensation.

Before you scoff at the concept of risk compensation (essentially the temptation, when you feel protected, to take more risks, and vice versa) you might wonder how your driving might be different if you were to travel at speed without wearing a seatbelt. (I don’t recommend you do this experiment – it’s illegal, if nothing else.) And it holds for the way other people perceive you, as well.

Whenever I get drawn into an argument about cycle helmets, someone will invariably regale me with the tale of how they (or someone they knew) fell off their bike and the helmet split and therefore the helmet saved their life. I do find it difficult to square the fact that this person never showed any sign of concussion with the observation that cycle helmets are not even designed to make the difference between no injury at all and a cranial lobotomy. But more worryingly this person – who is usually a reasonably well-educated scientist – not only appears to have an alarming propensity for falling off their bike but also seems to have forgotten what a ‘control’ is. Not just the control non-helmeted cyclist who fell off their bike, but the control who went out that day and both behaved differently and was perceived differently. My interlocutor seldom comments on the state of the polystyrene of the helmet, the force of the impact, nor the increased impactable area that a helmet affords.

I’ve also heard that neurosurgeons and nurses swear by cycle helmets and disapprove of you if you present in A&E without one. They, I presume, have performed the appropriate controls, otherwise they wouldn’t be so convinced.

I guess the biggest argument in favour of cycle helmets is that the one country where everybody cycles and almost nobody wears a helmet has one of the highest cyclist head injury rates in the world.

No, wait. One of the lowest. Sorry.

Richard P Grant used to cycle in Sydney, Australia, where the biggest risk is to life and limb is from drop bears. This post was supposed to be a summary of the evidence for and against cycle helmet use but you should probably check out the Bicycle Helmet Research Foundation yourself