Helmet battle flares up in BMJ

Australian statistician Dorothy Robinson has a cycle helmet anti-compulsion paper published in this week's British Medical Journal. Another paper, from four professors of epidemiology from Canada and the US, counters her arguments.
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Legislating to make bicycle helmets compulsory for all cyclists reduces bicycle usage and is bad for full-population health, argues Robinson.

This is a long held position, well known to helmet anti-compulsionists, but now given three and a half pages in the influential BMJ.

In June 2005, the doctor delegates at the British Medical Association's annual representative meeting voted yes to a motion calling for compulsory helmet wearing for cyclists.

At the close of the five-minute debate on the motion, Sam Everington, deputy chair of the BMA's council said: "We've had an enormous amount of letters about serious injuries caused by not using helmets."

He did not mention the March 2005 letter sent to the BMA by 45 doctors and PhDs, urging the BMA to reconsider its helmet compulsion position, now official BMA policy.

The list of docs on the letter included many experts, including a senior lecturer in paediatric pathology, a professor of medical statistics, a professor of medicine and metabolism, a consultant psychiatrist, a consultant in emergency medicine, and a consultant in public health.

The non-medical docs included a Fellow in system safety engineering, a PhD in risk assessment and a materials engineer.

And statisticians like Dorothy Robinson also worry about the "contradiction between predicted benefits from case-control studies but minimal changes in head injury rates when helmet wearing increased substantially because of legislation."

Robinson - a helmet-wearing cyclist - comes from the land of the helmet law and is senior statistician at the University of New England, New South Wales, Australia. She is an expert in statistical modelling, "especially how biased and misleading results can be obtained from fitting incorrect or inappropriate models."

Using crash stats from Australia and New Zeland she said there is no clear evidence that bicycle helmet laws improve public health.

She reviewed data before and after helmet legislation and believes helmet laws discourage cycling and produce no obvious response in the number of head injuries.

She said: "This contradiction may be due to risk compensation, incorrect helmet wearing, reduced safety in numbers (injury rates per cyclist are lower when more people cycle), or bias in case control studies."

She suggested that helmet laws are counterproductive and that governments should instead focus on measures that lead to huge drops in mortality figures, such as campaigns to deter motorists who speed, drink, and fail to obey road rules.

"Helmet laws would be counter productive if they discouraged cycling and increased car use," said Robinson.

"Wearing helmets may also encourage cyclists to take more risks, or motorists to take less care when they encounter cyclists."

Research from the UK's Transport Research Laboratory backs this up: motorists drive closer to cyclists who wear helmets, believing these cyclists to be more proficient and "protected" with safety equipment.

The medical academics from the US and Canada who argue against Robinson - including Frederick Rivara, author of a helmet paper which released the "85 percent of deaths would be prevented by wearing helmets" stat to the world, a deeply flawed stat, say anti-compulsion campaigners - argue that helmet compulsion is sound.

Assistant professor Brent Hagel of Montreal Children's Hospital Research Institute, and colleagues, said in a one and a half page piece: "Robinson's opposition to helmet laws is contrary to published evidence on the effectiveness of bicycle helmets. At least six independent studies have reported a protective association between wearing bicycle helmets and head injuries."

The authors appear to agree that helmet compulsion leads to a drop in cycle usage.

Their paper said "let's assume legislation does discourage a large proportion of cyclists. The crucial question is whether the decision not to ride, for however long, truly diminishes physical fitness. In other words is the trade-off between head protection and physical fitness worth it?"

So, from their point-of-view, it would be OK for helmet compulsion to lead to less cyclists because the ones that were left would be "safer." This is a position that ought to worry the bike trade. Any measure that leads to less cycling would be bad for the bike trade.

The British Medical Association famously said that the risks of cycling are far outweighed by the health benefits of cycling.

ROBINSON:

http://bmj.bmjjournals.com/.../DC1

RIVARA ETC:

http://bmj.bmjjournals.com/.../725

LOADS OF HELMET LINKS:

http://www.bikeforall.net/linkcat.php?cid=183

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