The has published a study which shows that cyclists who don't wear helmets are three times as likely to die of a head injury than those that do wear helmets. The lead researcher is quoted in the Globe and Mail:
“Helmets save lives,” said Dr. Nav Persaud, a family physician and researcher at St. Michael’s Hospital in Toronto, who led the study. "There are about 70 cycling deaths in Canada every year,” Persaud said. “And based on our study, we estimate we could prevent about 20 of them with helmets.”
Persaud does get that there is more to the problem than helmets.
"Helmets only prevent injuries after a collision takes place,” he said. “It would be better to prevent the collision from taking place at all. And infrastructure changes like building separated cycle lanes prevent collisions from taking place
There are a lot of others who note that helmet promotion creates a climate of fear, telling people that cycling is dangerous, and that mandatory helmet rules would take cyclists off the road, and that this would lead to worse overall health outcomes. Even helmet supporters note that all the responsibility should not fall entirely on the heads of the cyclists.
If I were going to wave my magic wand and make biking safer, I wouldn’t pick helmet legislation as the No. 1 thing to do,” [Alison] Macpherson [of York University] said. “I think it can be a part of a comprehensive approach to safe cycling that promotes cycling."
Indeed, this study shows that 77% of those deaths occurred because of interactions with automobiles. Another Canadian study shows that cyclists are responsible for only 10% of the bike-car accidents. No doubt there will be yet another call for mandatory helmet use, while at the same time the idea of reducing speed limits for cars is rejected.
Not wearing a helmet might increase the risk of death in an accident; that's why I am wearing one again. But surely the best way to reduce deaths is by preventing those accidents in the first place, instead of once again blaming the victim.