The tragic accident involved Natasha Richardson has lead to calls for helmets to be made compulsory when skiing. Would this remove all some of the pleasure of the activity? Should the olympic gold medallist have to use a helmet on a green slope?

According to a commenter on this article:

One eye witness report described her having a FORWARD fall: "She lost her balance and nosedived down the hill". That suggests her face and chin may have taken the first impact, then been forced back, like if someone pulls your head back from behind you, or in a shunt accident from behind in a car which causes "whiplash". That force can tear and rupture blood vessels at the base of the head/top of the spinal cord, which causes bleeding, clots and a build up of pressure on the spinal cord and up around the dural lining of the brain, which if not speedily relieved causes increasing headache and then unconsciousness, and ultimately a vegetative state and death. This accident does not seem to have been an "impact" type accident where a helmet might have offered some protection.

It seems to me that there is a balance issue here. It's true that skiing has risks associated with it, but there is a balance of risks. Whilst in this particular case a helmet may have helped, one has to look at the chances of such an injury. A small risk of a disastrous outcome may not override a certain risk of an inconvenience (that of not enjoying the mountain air as much).

In North America, there are a little over 43 serious injuries per year. This includes head injuries as well as injuries to the spine etc. Helmets would not help here. Let us assume that all of these were injuries which a helmet could protect from (as an overestimate). This gives 0.68 'head' injuries per million days of skiing. Swimming had 72.7 fatalities per million participants and 2081 fatalities for every million days spent swimming. Cycling in contrast had 29.4 fatalities per million participants (this is a stat for North America, in the UK the figure is about a third of that - it's lower still in the Netherlands and Denmark).

We don't ask swimmers to always use flotation devices (despite these being readily available) - what's the difference?

I'm not a skiier, but am a cyclist. On several reports I've heard this conflated with bicycle helmets (calls to make them compulsory).

I use a bicycle, and I do use a helmet - but I wouldn't want a law for that. Why?

Cycling Fatalities

This graph (source) shows that as the percentage of journeys made by bicycle rise, the number of fatalities per km cycled fall.

Is it a coincidence that the countries with helmet laws tend to have a lower percentage of journeys made by bike?

When looking at a population, if the effect of a helmet law is that fewer people cycle - this could save a few serious injuries at the expense of a general reduction in the amount of exercise taken. Hence, paradoxically, a helmet law could swap some obvious injuries for a greater number (though harder to count) of illnesses due to ill health.

On the CTC forum, Cunobelin points out that: "60% of head injuries are alcohol related...... how appalling that we have to pay for the injuries of people who have not worn a helmet in the pub!"

Helmet laws for cycling (and skiing, though personally I care not about that) could be counterproductive. In the case of cycling there is ample evidence around the world that not having such laws (as well as having good infrastructure) encourages cycling and reduces risks as drivers are more used to cycles on the road.

There is also evidence that cycle helmets, whilst giving some protection from linear impacts (i.e. the bash on the head), actually increase the incidence of injury due to rotation. This is because the skin can move relative to the scalp, but the helmet will twist the skull around.

Reducing bicycle accidents: a re-evaluation of the impacts of the CPSC bicycle standard and helmet use

Rodgers. Journal of Product Liability 11 pp307-17, 1988

To examine claims that growth in the use of hard shell cycle helmets had been successful in reducing cycle-related injuries and death, Rodgers studied over 8 million cases of injury and death to cyclists in the USA over 15 years. He concluded: "There is no evidence that hard shell helmets have reduced the head injury and fatality rates. The most surprising finding is that the bicycle-related fatality rate is positively and significantly correlated with increased helmet use". (source)

Aside: In finding some of the sources for this article, I stumbled across this page linking a rise in seatbelt wearing in motorists linked to an increase in danger to pedestrians and cyclists.

Returning to Natasha Richardson, I don't know for sure, but I wouldn't be surprised if there wasn't some other pre-existing weakness in the skull in her case. If so, would a helmet have saved her?