Never let your government get away with claiming that #bikeHelmets are "the first rule of bike safety".
Rule number one is infrastructure, and the 2nd is air+brakes+chain mechanical soundness of the bike, upright geometry of the bike, traffic awareness, ride with fingers on your brake levers and having practiced emergency stops, twenty is plenty... Helmets are for stunts or a footnote to "don't fall on your head" rule that applies to walking moreso than biking.
As an emergency physician, you presumably treated people who had been walking, swimming, climbing a ladder, or playing soccer without helmets, who suffered cranial hemorrhage as well. But I expect that for at least some of those activities you don't advocate helmets.
The question for me isn't just by how much a helmet would reduce the risk of cranial injury, but also how high it was to begin with.
The few studies I've been able to find that actually address the base rate of risk, leave me comfortable riding a bike for daily transport without a helmet.
From what I found, head trauma rate per hour of cycling seems to be a bit higher than walking, but the difference is less than the difference in speeds - meaning the rate per kilometer is a bit lower than that for walking.
I'd never discourage someone from wearing a helmet, but I'm OK accepting such a risk without PPE.
😀🚲
Kriky
dragonfrog