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Friday, July 27, 2007

How safe is cycling - An Epidemiologist's Perspective

With North American summer in full swing and the cycling season at its peak with Le Tour finishing up, we thought we would stay focused on cycling, but take a different look at the science behind it.

Epidemiology is the study of the factors affecting the health and illness of a population or populations. These scientists gather massive samples (thousands to hundreds of thousands of people) and look the different rates of incidence of whatever they are interested in. When you read statistics in articles that say your chances are "3.4 times higher" for getting a disease, or the number of people with an illness is "23 per 1000 people," we have the epidemiologists for working these out for us. In Exercise Physiology, we are often interested in the rates of injuries in certain sporting populations, and how much greater the risk is for certain injuries between sports. Dr. Lara Dugas is an Epidemiologist at Loyola University and a cycling fan (and Jonathan's wife!), and she brought this study about traumatic brain injuries to our attention.

You can read the article to learn how they collected the data, but the take home message is that traumatic brain injuries (TBI's) from cycling account for only 7.7% of the total number of injuries sustained from that sport. So there were nearly 525,000 cycling injuries reported in this study, and about 40,000 were TBI's. When we compare this to playing on the playground, for example, the incidence of brain injuries is very similar (7.1%). Therefore we can conclude that whether you injure yourself on the playground or on the bike, the chances that your injury is a TBI is similar between the two activities.

In addition, 5-18 year olds account for 59% of all cycling injuries, and this age group also accounts for 57% of all TBI's in cycling. So adults are at lower risk for TBI's then those under the age of 18.

And the higher risk sports, you ask? Well, TBI's in horseback riding make up 11.7% of the total injuries from that sport, and TBI's make up 10.4% of the injuries sustained during ice skating. All the other 25+ activities fall in the 1-6% range, with TBI's in Track and Field making up only 1.8% of the total number of injuries sustained during that particular activity.

Of course we all know that wearing a helmet while cycling---even when just cycling to the store down the road---greatly reduces your risk of any kind of head injury. Having said that, it is amazing that the state of Illinois (and probably many others in America) do not have any kind of helmet laws for bicyclists or motorcyclists, although for races sanctioned by USA Cycling helmets are obligatory. Previously the UCI allowed professionals to remove their helmet on the last climb of the day if it were a mountain top finish, and also their time-trial helmets did not have to actually be a helmet----instead they were just an aerodynamic foil with no protection in them! Fortunately in recent years the UCI has introduced rule changes that require professional riders to wear their helmets for the entire duration of a race, which ultimately has a large "impact" on their health and influences the behaviour of amateur cyclists everywhere.

Enjoy the time trial on Saturday, and don't forget to vote in new poll!


PecosPeet said...

>>In addition, 5-18 year olds account for 59% of all cycling injuries, and this age group also accounts for 57% of all TBI's in cycling. So adults are at lower risk for TBI's then those under the age of 18.<<

Did this study properly account for the different incidence of cycling by age? I would expect a much greater percentage of those under 18 cycle than for those over 18. And then one should consider the time spent, distances covered, and type of riding involved.

Tha said, intuitively I would agree with the findings, but there is so much room here for misaaplying statistics, one must be very carefull!

Ross Tucker and Jonathan Dugas said...

Hi Pecospeet,

Thanks for your comment and for visiting us at the Science of Sport.

Who was it that said, "There are three kinds of lies. . .Lies, Damn Lies, and Statistics!"

Your point is well taken about mis-applying the stats. Especially in epidemiology this can be done all too easily. It does NOT appear that this study account for the different incidence of cycling by age. It appears that they gathered records from hospital and ER visits, and analyzed that data alone without any information about the number of hours each age group spends in each sport.

Excellent point, and we hope you contribute your viewpoint to our future posts.

Kind Regards,
The Sports Scientists

Unknown said...

An interesting twist on whether helmet use could increase your risk of collision with a vehicle.
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