Laws Based on Lies?

“65% of statistics are just made up.”  — unknown

It’s been repeated so many times as to be considered a “fact.”  But this “fact,” which has been used to justify mandatory helmet laws across the nation and around the world,  is based on a misleading report about a poorly designed study.  I’m speaking of course about the “fact” that bicycle helmets reduce head injury risk by 88%. This paper does a great job of explaining the errors in the infamous Thompson, Rivara & Thompson study, published in New England Journal of Medicine in 1989. The key shortcomings:

• The “cases” (bicycle head injury hospital admissions) were significantly different in character from the “control group” population.
• None of the cases involved bicyclist crashes involving motor vehicles.
• The report is claimed to apply to all ages, but the case and control groups were all children.
• Helmet use was “self selected.”  Non-head injuries were less severe among helmet-wearers than non-helmet-wearers, implying that helmet-wearers are less likely to get involved in more serious collisions.

According to the Florida Department of Health, there were 622 traumatic brain injuries (TBI) among bicyclists in Florida in 2005.  By comparison, during the same period, 14,696 automobile and truck passengers, 1,643 motorcyclists, and 1,189 pedestrians suffered traumatic brain injuries.  Cyclists were only 3% of all traffic-related TBIs.  The TBI rates per 100,000 population* (2005 thru 2007) are: motor vehicle occupant 82.5, motorcycle 10.7, pedestrian 7.1, bicyclist 3.7.  (That’s total population, not “cycling population” or “motorcyclist population,” etc.)

[The above paragraph has been updated with better data.  The previous numbers were from a report that evidently only included injuries recorded in the state's "Central Registry."]

Since helmet use is such an important element of the “dangerization” of cycling, we owe it to ourselves to do what we can to smack down those ubiquitous “88%” claims whenever we can.

Obligatory Disclaimer:  I am not anti-helmet.  I wear one most times I ride.  I am anti-helmet law because there is some evidence that such laws reduce cycling (especially among kids) and because there is no evidence of a compelling state interest.

Posted in Bicycles & Equipment, Safety