There have actually been studies done on this. The estimate I’ve seen is that for every year of life that would be prolonged by mandating helmet use in NL, 25 years of life would be lost from the loss of exercise by people who don’t take bike trips because they are put off by helmet wearing. This is a real thing that has to be taken into account.
The other interesting stat is that an hour of bike riding in NL carries approximately the same risk of head injury as an hour in a car in the USA. So, should we make all car passengers wear helmets? It would make them safer…
Would helmets in cars make them safer though? It's a different risk profile; I don't think you tend to fall out of your cars and hit your head?
I can't find any stats of prevalence of various types of injuries in cars, although it does seem to be a thing to get brain injuries in cars (whether that is due to impact or neck/head stopping I don't know)
TBH, I'm not in favor of requiring helmets, but given the fact that balance does tend to decline with age, I think that recommending that older cyclists ride trikes instead of bikes would be a good idea. Falling off of a trike is less likely.
The other interesting stat is that an hour of bike riding in NL carries approximately the same risk of head injury as an hour in a car in the USA. So, should we make all car passengers wear helmets? It would make them safer…