A new study claims that making cycle helmets compulsory would have a detrimental effect on a country's overall health.
The report by Piet de Jong, a mathematician at
But it says these would be tiny in comparison with the costs and the effects on health of the associated drop in cycling.
The professor of actuarial studies estimates that bicycle helmet laws would cost the US $4.8 billion (£3.2bn) per year,
The results have proved contentious because they are based on projected figures. De Jong himself admits: "There's a lot of uncertainty around it. I try to reconcile all these various numbers or proportions that impinge on the question of whether helmet laws are very useful."
The professor says that in order for mandatory helmet laws to be beneficial for a nation's healthcare system, head injuries must be a substantial proportion of cycling injuries, few riders must abandon their bikes due to helmet laws, and the health benefits of cycling need to be low.
"Even under very favourable assumptions to the pro-helmet lobby group, it's very hard to get a benefit," he concludes.
Previous studies have tended to concentrate on particular consequences of compulsory helmet wearing, often concluding in favour of the 'pro-helmet' lobby. For example, a 1989 case-controlled study (i.e. directly comparing helmet wearers with non-helmet wearers) published in the New England Journal of Medicine concluded that bicycle helmets reduce the risk of head injury by 85 per cent.
Writing in the British Medical Journal in 2006, Dorothy Robinson, a statistician at the Department of Primary Industries in
Robinson's point seems to have been backed up by evidence from 1990 – Victoria, Australia, introduced an all-ages cycle helmet law in that year and helmet use rose from 31 percent to 75 percent, with the number of head injuries dropping by 40 percent.
However, cycle counts in
De Jong believes the 1989 study was overstated, and says: "Everybody takes one piece of the evidence and nobody is really putting in all the pieces of the puzzle."
However, Barry Pless, a director at Montreal Children's Hospital with a special interest in research on child injury prevention, says de Jong's model overvalues the health benefits of recreational cycling.
He says most riders travel short distances rather slowly, blunting some of cycling's cardiovascular benefits. Pless cites a study of 9,000 UK government employees which found that people between the ages of 45 and 64 needed to pedal 40km per week to see any reduction in heart disease rates.
De Jong, originally from the