Bike helmets: an emergency doctor’s perspective

For those working on the frontline of trauma care, the findings of a report into the protective effects of helmets in cyclists and motorcyclists published in the Medical Journal of Australia last week come as no surprise.

When an ambulance arrives at an emergency department with a cyclist injured on the road, a clinician needs to first know a few important details. How old is the patient? What are the vital signs? And finally … were they wearing a helmet?

That’s because ambulance officers, doctors and nurses have known for a long time that if a helmet is not being worn at the time a head strikes the road, pavement or cycleway, the chances of severe head injury are much higher.

Now this been shown in a one-year study I conducted, with two colleagues, of injured cyclists and motorcyclists presenting to seven major trauma centres in Sydney.

The risks of severe head injury were more than five times higher in cyclists not wearing a helmet compared to helmeted ones, and more than three times higher in motorcyclists not wearing a helmet at the time of injury.

Severe head injuries were defined as any with significant brain haemorrhage, complex skull fracture or brain swelling.

Some 70% of such patients end up on a ventilator in intensive care units; many patients with severe head injuries are left with permanent brain damage.

It’s estimated that each new case of severe brain injury costs Australia A$4.5 million.

But it’s the things that can’t be calculated that are perhaps more crippling – the long-term personality changes, the seizures, the post-traumatic adjustment, and the interminable stress on family and carers.

Conflicting studies

Australia is one of the few countries in the world with mandatory helmet laws protecting both motorcyclists and pedal cyclists.

While helmet use in motorbike riders is generally accepted, compulsory helmet laws have been resisted by many experts.

Many argue that helmet use simply deters people from dusting off their two wheelers and pedalling their way to better health.

Using a telephone survey, Professor Chris Rissel from the University of Sydney concluded that cycling rates could increase dramatically if mandatory helmet laws in Sydney were repealed.

In contrast, a recent National Heart Foundation survey showed that overall road safety, road speed and the presence of dedicated bike paths were the main obstacles limiting bicycle use.

Only 17% of respondents identified helmet use as a potential factor.

Turning the tables on rotational injury

Publicised court cases testing Australian helmet laws have even invoked limited autopsy reports hypothesising the effect of helmets imparting “rotational forces” on the brain, causing diffuse axonal injury.

Diffuse axonal injury is widespread (rather than focused) damage to the brain, and is one of the major causes of unconsciousness and persistent vegetative state following head trauma.

The argument here is helmets apparently exacerbate head injury severity by causing the head to twist quickly on impact, thus creating rotational forces on the brain.

There have been no controlled studies in the clinical setting into the association between helmet use and diffuse axonal injury – until now.

We found no reports of diffuse axonal injury in pedal cyclists, helmeted or non-helmeted, and only a marginal increase in such diagnoses in non-helmeted motorcyclists.

Definitely worth helmet hair

This Sydney-based study was the first to place motorcyclists and pedal cyclists side by side and demonstrated that the protective role of helmets in both groups are important – and even better in pedal cyclists.

Helmet hair is a small price to pay for protection. mrlerone

These results are within the range reported by a Cochrane Collaboration systematic review on the subject as well as a study of more than 13,000 pedal cyclists in France published in 2012.

Some experts against this type of observational research cite small sample sizes, and flaws inherent in case control studies, such as not being able to take into account factors such as speed and intoxication.

But it is also true that the very same type of observational study designs was the basis on which the association between smoking and lung cancer was first described.

Once you get enough studies pointing in the one direction, the signal becomes harder to refute.

If mandatory helmets are good enough for motorcyclists, they’re certainly good enough for pedal cyclists.

And as more and more people use bicycles to go to work, work up a sweat or just spend time with the kids, they can rest assured that the helmet resting comfortably on their head is doing something much more than simply disrupting their hairdo.

Michael Dinh does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published at The Conversation.
Read the original article.

Arfy

My understanding is that severe head trauma is more commonly associated with cyclist v’s motor-vehicle accidents than other types of accidents where broken bones such as collar-bone injuries are more prevalent. I’m interested to know if your study was able to shed any light on the truth of this statement?
Shane

I have been cycling competitively for over 25 years and accidents happen when you least expect them. Just last week I was returning home from a 100k ride and to warm down and avoid as much traffic as possible I use the bike track along the Cooks river as I passed under the railway line near Tempe station I slowed down to 10/15k’s as that section floods from the river and is always mucky and slippery. As I turned a corner my front wheel went from under me and I hit the deck so fast my hands were still on the bars. My elbow, hip and head took the impact cracking my helmet. I have replaced around 5 helmets over the years very happy to do so.
Geoff

I believe that statistically, the approach taken is fundamentally flawed. What the study found was that head trauma was less severe amongst cyclists wearing helmets. What this doesn’t explore is whether the wearers of helmets are a self-selecting group who inherently take fewer risks - i.e. the reduced trauma was not inherently because of the helmet (which may have still had a positive impact) but rather because a person who wears a helmet is more aware of the risks involved in their activities and has taken other mitigating actions.

In Australia, because of helmet laws, most people who do not wear helmets are people who are comfortable with the risks of a fine for not wearing a helmet. I would hazard a guess that the kind of person who does not wear a helmet, and is comfortable taking the risk of a fine, is also comfortable taking more risks in his or her riding behaviour, and as a result is more likely to engage in riding behaviour which is likely to result in a serious accident. This potentially invalidates any comparison of the injuries experienced by wearers and non-wearers of helmets, because those cyclists who use helmets have probably taken other actions to reduce their risk of trauma, or reduce the level of trauma if they do crash.

I don’t know if there is any way of obtaining a statistically valid sample.

FWIW, I don’t venture out on a bike or go climbing without a helmet.
- Nic_3
  
  I think you are wrong to say that the mere presence of potential confounding factors invalidated a comparison.
- PT
  
  I understand your point but even if you’re right, its not a necessary consideration. Helmets reduce brain impact, no matter what your behaviour or preference WRT risk. Studies are interesting and can be dissected this way and that but it just comes down to protecting your head from impact. Witness just damaged skull/brain from impact without a helmet and I’ll bet we all will happily accept N=1.
  
  Damaged brains are not good for anyone.
- jules
  
  this is a valid point, except that i’d argue the reverse is more likely. unhelmeted riders around where i live tend to be non-competitive commuters tootling around at 15 km/h. by comparison, roadies wear helmets and take more risks. by way of example, apparently the Alfred trauma dept was filled with riders from the SKCC crit “world champs” earlier this year…
- Arfy
  
  Have a look at a report commissioned by the City of Toronto (Canada) titled “Toronto Bicycle/Motor-Vehicle Collision Study (2003)”. For some reason this comments section won’t allow me to put the URL here, so try googling it. The Executive Summary has a table of all collisions segmented by cause, and the overwhelming majority of accidents were caused by motor-vehicle drivers, not cyclists (erratic or not). There are other studies that show similar results, and that also show that the majority of cyclist head-trauma accidents involve a motor-vehicle.
  
  While as cyclists it’s only prudent to maximise our visibility and protection, we cannot directly control the actions of drivers that put us at risk. This is where we need our governments to stand up and provide decent on-road bicycle facilities that properly segregate cyclists and motor-vehicles. They need to stop hiding behind the smokescreen of the helmet argument and start putting effectual preventative solutions in place.
  - Geoff
    
    I think you’ve touched on a very important point here: in my opinion helmets help to reduce head trauma (this is a subjective opinion). Regardless of the benefits of helmets, any initiatives which reduce the number accidents involving vehicles and cyclists will do far more to reduce cyclist head trauma than helmets can. Mandatory helmet laws give politicians a false sense that they have done something constructive, when in fact they haven’t. Adequate cycling facilities plus proper education of drivers and cyclists to share the roads will reduce cyclist head trauma (by preventing accidents) more than helmets ever can.
    
    I tend to take the view that enough cyclists are rational enough to understand that they should wear helmets. We don’t need politicians telling us to do that. The politicians, on the other hand are sitting on their hands when it comes to issues like driver education.
- Drug Pedaller
  
  Welcome to the world of observational research Geoff. Now, if only somebody would do a randomised controlled trial of helmets vs no helmets powered to show a 5 - fold difference in severe brain injury…
http://twitter.com/_TomWard_ Tom W

Forgive me for stating the obvious. But how can this study be conclusive when helmets are mandatory in Australia, making one of the statistical groups lacking in numbers?
There have been many studies in the UK on the very same, and the EU and the UK combined have determined that the wearing of helmets is the choice of the rider.
This article only talks about the impact of a helmet wearing cyclist sustaining a rotational brain injury which would not occur without a helmet, however it doesn’t address the obvious reason for Aquired Brain Injuries in cyclists, in that you have deceleartion injury which a helmet will absorb some of the impact, but depending on the nature of the fall, may not. We all know from experience that the most painful of falls, tends to be that at lower speeds where you drop to the ground without forward momentum.
Foreign observer

There are 9000 deaths from inactivity in Australia each year, and 35 or so from cycling. These are pretty easily googled government stats (from .gov.au sites in first few hits for appropriate searches).

If your helmet law saves, say, ten cyclists from death a year (that’s a VERY generous allocation), then it has to prove that it doesn’t increase the inactivity death rate by 0.1%. I think that’s a very tough burden of proof.
- PT
  
  Ok, if that’s too hard, try 10 x $4.5million ($45m) in costs associated with brain injury. Except that the 10 is your figure for deaths so the group who get injured but don’t die might be higher
redleicester

Helmets saves lives, so should also be worn by pedestrians, drivers, around the home and while performing any sex act on wet grass.

Bike helmets: an emergency doctor’s perspective

By Michael Dinh - May 7, 2013

Conflicting studies

Turning the tables on rotational injury

Definitely worth helmet hair