April 1, 2011

Thoughts On That Helmet Article…

Thoughts On That Helmet Article...

An article in Ski Canada Magazine examining helmet use stats in the US is generating quite a bit of buzz right now in the ski world. I've read the article and given it some thought, and my impression is that it's easy to misread and/or misinterpret the article's conclusions. Let's take a closer look at what the authors wrote:

The article's bombshell observation is that an analysis of raw data from a US ski area from 1991 to the present (?) indicates the rate of skier fatalities has remained relatively constant despite a significant increase in the percentage of riders who wear helmets. The obvious inference here is that helmet use has therefore not had any positive impact on skiing safety—but hold that thought!

The authors also cite a study indicating that (1) there is no advantage to wearing a helmet in soft-snow collisions; (2) in hard-object collisions (ie, trees), a helmet significantly reduces harmful forces to the brain, but collisions remain fatal due to associated trauma to other parts of the body; and (3) in hard-snow collisions, helmets significantly reduce harmful forces to the brain—potentially enough in some situations to reduce or prevent actual brain injury.

What are we to make of this?

First of all, anytime you see a statistical analysis in any literature, you should automatically be skeptical of its validity. For the short explanation of why this is so, it's because statistics is a complex field that is really, really hard to get right—even for experienced statisticians. For a more in-depth exploration of this fascinating subject, see The Drunkard's Walk (highly recommended). So let's reconsider the article's evidence, which seems to indicate helmet use hasn't had any impact on skier fatalities.

What leaps out at me is that during the time period in which the article's data was collected, the sport of skiing was undergoing a period of explosive change. In other words, the analysis does not control for other variables. For example, 1991 roughly corresponds to the arrival of terrain parks in US ski areas. Presumably, terrain parks have made skiing much more dangerous, so maybe helmet use has prevented a big spike in skier fatalities.

Alternately, consider that 1991 corresponds roughly to the arrival of shaped skis, which have made skiing much, much easier and therefore presumably much safer. So maybe helmet use has caused a big increase in skier fatalities, luckily counterbalanced by modern ski technology. There you have it: two exactly opposite conclusions drawn from the same data set.

And one last observation: looking at skier fatalities alone tells us absolutely nothing about the incidence of permanent or otherwise debilitating brain injuries suffered during the study's time frame, which, given modern medical advances in keeping head trauma cases alive (post-Iraq), could be the single most important metric of all.

My take is that any conclusion based on the apparent lack of correlation between helmet use and skier fatalities is hasty at best. If you are currently wearing a helmet when you ride, I see no reason here to stop wearing your helmet. Conversely, if you do not wear a helmet, I find no conclusive evidence here (or elsewhere) suggesting you should start wearing one. Yes, the one clear finding of the various studies cited is that helmets offer a significant reduction of harmful brain forces in most collisions. But it's just not clear whether or not that translates into a meaningful benefit for real skiers in the real world.

As the Ski Canada Mag article's author emphasizes, skiers and snowboarders need to be aware of what helmets can and can not protect against. Hard-object collisions at typical skier speeds will often be fatal regardless of helmet use. Hard-snow collisions (take note park riders!) would seem to be the modality in which helmets offer the greatest potential benefit. Whatever you decide, I encourage you to stay open-minded on the subject of helmet use, and avoid drawing hasty conclusions in either direction.

  1. tim says:

    Being a statistician means never having to say you’re certain. However, it also means making observations that are most likely to be true in the long run (i.e., as N->infinity). If the rate of fatal incidents in collisions with hard objects is static, that suggests that thoracic trauma or other non-cranial factors are typically to blame. (Side note: read Ammon McNeely’s essay “Full Value” in an old issue of Alpinist, I think #25, for an example of someone who would not be around anymore if he had not worn a helmet… which failed, but in doing so, kept Ammon alive).

    From the article:
    > The public expects far more than a helmet could
    > ever be expected to deliver. Most famously, the
    > U.S. Consumer Product Safety Commission (USCPSC)
    > as much as promised in 1999 that if everyone
    > wore a helmet while skiing and snowboarding,
    > there would be no more head-injury deaths on ski
    > slopes.

    Aaand there you have it. Helmets designed for impacts at 10mph are unable to prevent the sort of trauma associated with deaths from impacts at 50mph, especially against a rock, a rail, or a tree. Either helmets need to be designed like motorcycle helmets, or people need to quit expecting them to prevent fatal g-forces and nasty sequelae like subarachnoid hemorrhages.

    Just because you’re clipped into a climbing rope doesn’t mean it’s a good idea to fall on ice. (And just because you’re likely to get badly fucked up in an ice fall, doesn’t mean that most people are going to solo ice climbs… it’s an issue of getting fucked up vs. dying on impact)

    Likewise, wearing a helmet is no substitute for good judgment. Aaand good judgment is no substitute for wearing a helmet. Best results are achieved by a combination of the two.

  2. Dan Conger says:

    I religiously wear my helmet, and I intend to continue doing so. I’ve had my “bell rung” as a result of falling while skiing, and the helmet has prevented a repeat of that despite a few big wipe outs. If I fall (say on Hangman’s or Paranoids at Mammoth), and roll-over to self-arrest, a helmet protects my head if my intentional roll-over were to take place on or near rocks. Self-arresting is a far better option than sliding off downhill at tremendous speed. However, it is only if I fall at a reasonable speed that my head is protected … and it’s only my head. Collisions with other skiers, trees, boulders, or falling from a great height may still kill me.

    I think something the article clearly misses in its statistical analysis is the growth in the population of skiers/riders during the time period from 1991 to present. Skier/rider population has absolutely exploded during that time frame. So, if the number of fatalities has remained constant, but the overall population of skiers and riders has dramatically increased, then that in and of itself could suggest that helmets are preventing fatalities.

    Another thing to consider is the explosion of more extreme forms of skiing/riding. I grew up in Bishop, CA near Mammoth. As a teen, my time was spent bouldering the Buttermilks, mountain biking, hiking, and skiing. Terrain parks were just starting when I graduated from high school in 1995. Early in my skiing days (as a child), there were literally signs at Mammoth that said, “No Jumping.” Now, they build gigantic table tops and encourage people to fling themselves 50 or even 60 feet into the air, where a wipe out could be fatal helmet or no. When I was a kid there, it was uncommon to see people performing cliff jumps, straight-lining massive chutes, or launching off of 60 foot table tops. Now, it is a daily occurrence. Many more people take far greater risks on a daily basis when they ski. The reason why is debatable (although I feel I have a good idea), but the reality is what it is. As a result, I’m forced to conclude that not only is there an overall increase in the number of skiers/riders at resorts, but also those that do ski and ride are taking far greater risks on a daily basis (as Andy mentioned). If skiers and riders are frequenting the slopes in greater numbers and at the same time taking greater risks, but the number of fatalities has remained the same, that becomes another sign suggesting that helmets save lives.

    Look, people want some kind of panacea … some magic button to press that will deliver them from any and all danger and provide miraculous results. However, the back of the ski lift ticket at virtually every resort says the same thing. Skiing is a hazardous sport. Falling may result in injury. Etc. Use the equipment to stay safe. Exercise good judgment when taking risks. Do not assume that because you are using pro-level equipment that you can suddenly magically exhibit pro-level skills. As for me, my helmet stays on. I haven’t rung my bell one time since I started wearing it and I strongly believe that it will help save my life if need be.

  3. Travis says:

    Thanks for the analysis. I agree with your opinion and would take it one step further and say it is flawed. Like you wrote, the survey was conducted in a period in which the industry started to promote a very aggressive style of skiing and snowboarding. Like Dan, I remember the days when you would get your ticet clipped for jumping rollers or cutting through trees. Now we’ve gone to the extreme end without making it clear that each rider needs to ride at his own discretion. Second, the introduction of terrian parks must also be factored in. Finally, the helmet and the type of fall must also be looked at. My helmet has worked when I fall backwards, but the front of my face is completely unprotected. The bill of the helmet would have first impact, but if I hit the right patch of ice, I could easily break my nose, chip a tooth, bust my chin open, etc.
    My personal philosphy has always been for defensive purposes; I wear a helmet to protect myself from other riders. I know exactly what I am capable of as a resort skier, but I have no idea what everyone else is doing. Growing up so close to Mt High, I witnessed an amazing amount of collisions, and most times it was someone who was out of control hitting someone in front of them. This type of accident is almost impossible for the victim to prevent. All you can do in that scenerio is protect yourself in a reasonable manner before getting on the mountain.

  4. Andy says:


    The thought of someone else smashing into me is one of the scariest scenarios I can envision at a ski area. Which is why I always ski ultra fast when I’m not helmeted–so no one else can catch me! :)

  5. tim says:

    Why would you fall on a bunny slope like Paranoids? ;-)

    I pussied out on the Girly Man chute on Saturday because I didn’t feel comfortable skiing it in the condition it was in (or the condition I was in). Two other people (Dave and Al, both stronger skiers than I am) descended without helmets and without incident. I don’t question their judgment, and I wouldn’t have descended it even if I had brought my helmet. Andy chose to ski a different chute (can’t recall whether he wore a helmet) but the point is that one person might get jacked up with a helmet in a situation that another person has no issues handling without a helmet. Or a low-probability high-consequence objective hazard could render the calculation moot.

    This is not a safe sport, helmets don’t change that. I’ve walked away from a number of violent collisions involving bicycles, flipped cars, chopped ropes, and enormous (roped) falls. My luck has to be running out by now, and since I have a kid, I try not to risk too much on having a good time. (I also don’t want to waste my life by risking nothing, so it’s a balancing act)

    There is no price you can pay and no course of action you can take which will wholly assure your safety. We’re all going to die, some sooner and more traumatically than others, but the best any of us can do is to decide in accordance with our priorities and let the chips fall where they will.

    Andy McLean once did a back-of-the-envelope comparison between alpine climing, ski mountaineering, and cave diving, in terms of insurable risks. I think climbing came out as safer than ski mountaineering, which was safer (only just) than cave diving, but given the company we keep, please don’t ever imagine this is a safe sport. Pieces of foam and plastic can keep you from getting hurt worse than you might otherwise, but there is nothing that can make objectively hazardous sports completely safe. (And let’s admit it, that’s part of the attraction)

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When there is snow, SierraDescents is Andy Lewicky's California backcountry skiing and mountaineering website. Without snow, sierradescents becomes an ill-tempered hiking and climbing blog.

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