rmurphy195 wrote:It's a good article but unless I've missed something, the section in the published article reworking backwards from hospital admissions does not or cannot take into account the number of people who've fallen, bumped their head and as a result of wearing a helmet have no need to go to hospital in the first place. i.e. a minor bump does not result in an injury where it would have without a helmet (e.g. helmet scraped instead of scalp). This is an aspect that seems to be missing from many of the discussions I have read, as is the value of a helmet for injury reduction
The trick with population data is that all the incidents, or indeed non-incidents, are in it. If helmets are removing serious injuries and downgrading them to minor ones then there should be a drop in serious injuries as helmet use goes up. But there isn't.
rmurphy195 wrote:I have seen the result of a serious collision between a cyclist and a large cast-iron gate as found on many larger properties - in this case she failed to negotiate a sharp bend at the bottom of the hill and went into the gates head first. She had concussion and some bruises and had to go to hospital - but the helmet was completely split. I couldn't help wondering if without the helmet, her head would have been split and after the hospital visit the next stop would have been the morgue, not her home. There is no doubt that the helmet reduced the severity of the injury she would otherwise have had.
There are various problems with this. First of all, it's an anecdote and while anecdotes often inform personal decisions they're not really much use at this level, which is why epidemiology isn't interested in them. Next up, while it is often assumed that a broken helmet would have meant a broken skull it's around an order of magnitude harder to break a skull than a plastic hat. Another point is that if you whack a hat hard it tends to undergo brittle fracture which absorbs remarkably little energy. And actually you can't be sure (really, absolutely sure) it must have helped. Aside from various mechanisms for extra leverage from the greater size or similar, part of the issue is whether or not you have an accident in the first place. People using PPE have been observed to (on average) take more risks, which means more accidents.
rmurphy195 wrote:Which leads on to another aspect of many of the discussions I see on this and other forums - we see a lot of comments about risk, but when I did risk analysis at various depths as part of my job, there were 2 initial aspects - What is the risk of something happening, and what is the impact if it does. Then we go onto to mitigation or redesign strategies based on a combination of the score (High risk + high impact = 9), or the level of impact ("It's got a low risk of happening but if it does the business fails, so we'd better think of something").
For me the risk of falling and banging my head is small - it hasn't happened yet even though I've gone over the bars a few times in the last 50 years. But the impact of landing on my unprotected head is severe.
be, but actually people have been banging their unprotected heads against hard surfacers for as long as there have been people, and thanks to evolution they have, more often than not, survived. The impact of landing on an unprotected head is typically a headache. And the flipside is that excrement does of course happen and trips and falls are the biggest cause of traumatic brain injury... yet aside from individuals with very unfortunate conditions pretty much nobody uses such a thing when walking, because they know it's safe enough
rmurphy195 wrote:So the mitigation is - a helmet reduces the level of injury. And the injury might be - at night, the difference between falling, getting up and limping to the side of the road, and lying unconscious/semi conscious until hit by an approaching vehicle whose driver does not see me - maybe 'cos he's avoiding something which is lit (the bike with it's lights) and hits something which is not (Me!). (Mitigation = light clothing, white helmet!)
if there was a significant chance of your helmet making that sort of difference we would see it in a lessening of KSIs as helmet wearing goes up. But even where it's doubled overnight there is no such effect observable. Alternatively your helmet might make the difference between a driver overtaking too close and having you off, and giving you a wider berth because you're "not safe without a helmet". As you mention above, you have to factor in the chances of the accident happening at all.
The bottom line is that while we can reasonably say there are situations where you'll almost certainly be better off in a helmet (say, warding off a gnarly branch while doing a bit of singletrack), as far as setting out on the roads are concerned A Notional Cyclist is no more likely to end their journey in A&E with a serious injury if they set off without a helmet. That may be counter intuitive, but that don't mean it ain't so.
And, as is often the case, we need to look across the North Sea and get a sense of perspective. Despite their much vaunted cycle-friendly infrastructure there is nothing stopping Dutch cyclists falling off their bikes and hitting their heads. They might be less likely to be knocked off by motor vehicles, but then as the original British Standard noted cycle helmets are built for accidents involving low speed falls and no other vehicles. Ride along a crowded fietspad in a major town, perhaps sharing it with lots of kids on their 'phones while giving their mates backies, and you realise that for the sorts of incident helmets are designed for there's no shortage! yet wearing rates are well below 1%, and it's in terms of serious head injuries it'll be as safe as anywhere in the world. If there was a significant safety gain from helmets in simple falls the Dutch would have several million more reasons than most to be enthusiastic advocates, but they by and large don't bother, and the government does not encourage them because they realise it discourages cycling.
Often seen riding a bike around Dundee...