Originally Posted by Mojomarc
I won't even get into the hypothesis that helmets make people ski more aggressively...
Then kindly allow me
Originally Posted by catskills
The Hidden Danger of Wearing a Helmet. You say what is dangerous about wearing a helmet? How could a helmet be dangerous? Read this TIME article on The Hidden Danger of Seat Belts. http://www.time.com/time/nation/arti...?cnn=yes...For
the sake of argument, offers Adams, imagine how it might affect the behavior of drivers if a sharp stake were mounted in the middle of the steering wheel? Or if the bumper were packed with explosives. Perverse, yes, but it certainly provides a vivid example of how a perception of risk could modify behavior.
It’s hardly revolutionary to suggest that people will adjust their behavior according to their risk perception, but it’s quite a leap to go from that rather mundane observation to the assertion that risk interventions such as helmets may increase risk-taking behavior. That largely discredited assertion is known as the risk homeostasis hypothesis
(RHH, also known as the risk compensation hypothesis
). It postulates that accident or injury rates will remain relatively constant with the introduction of safety measures because the perceived reduction in risk will lead to proportionately increased risk-taking behavior. So, claim RHH advocates, as the use of helmets reduces skier and snowboarder head injuries, skiers and snowboarders will collectively change their behavior so that their overall risk as measured by injury rates will remain constant. On an individual basis, according to the RHH, you will likely decide to ski or snowboard more recklessly if you perceive a reduction in your risk of serious head injury by wearing a helmet, and you will ski or snowboard just recklessly enough to roughly compensate for the perceived increased protection. You won’t really care that your more reckless skiing will increase your chance of other serious injuries because you seek a certain level of injury risk when you ski or snowboard.
Is that really supposed to be how people think? Is that really how you think? Do you ski because you seek a set level of risk? Recall the last time you introduced some safety measure to your skiing, be it the first time you put on a helmet or the last time you had your bindings serviced; did you really find yourself thinking something along the lines of, “Now I will engage in greater risk-taking behavior and ski more recklessly to compensate for the safety intervention I just introduced
”? Even assuming that the greater risk-taking behavior may not be individually recognized because the decision-making analysis takes place on an unconscious level, it seems unlikely that humans can collectively and consistently perform the complex calculus necessary to synchronize risk-taking behavior to the roughly zero-sum injury rate changes required by the risk homeostasis hypothesis; there are simply too many shifting variables and confounders.
Hypothetically, the risk compensation for helmets is supposed to arise from the perception of a lesser risk of injury with helmets leading to greater risk-taking behavior, but the putative mechanism for this collective feedback remains something of a mystery. The feedback mechanism has been described as "similar to a thermostat", but this vague analogy merely reveals one of the risk hypothesis’s major weaknesses. A thermostat has a well-defined feedback mechanism—thermostats send signals to furnaces or air conditioners to produce more heat or cooling, and the subsequent temperature changes then alter the signals sent by the thermostat—but there is no plausible feedback mechanism that can signal individual skiers and boarders to take more or less risk to ensure that their overall injury rate remains constant.
The risk homeostasis hypothesis is not well-supported by empirical data. Professor John Adams
, cited in the link to the Time
magazine article in the quote above, has apparently called upon the risk homeostasis hypothesis to explain why mandatory seatbelt laws were not accompanied by a reduction in motor-vehicle fatality rates in certain countries. But how is the risk homeostasis hypothesis explanatory for those regions (such as in the USA) where the introduction of mandatory seat-belt laws was accompanied by a reduction in traffic fatalities and where multiple studies have not found any significant support for the compensating-behavior hypothesis? How does the professor and the risk homeostasis hypothesis account for the fact that the motor vehicle crash death rate per capita in the United States dropped 26% between 1966 and 1987, and then dropped another 18% over the next 2 decades? According to the risk homeostasis hypothesis, those rates should have remained roughly constant.
When it comes to skiers and snowboarders, the evidence does not support the risk homeostasis hypothesis, either:
Accid Anal Prev
. 2005 Jan;37(1):103-8. The effect of helmet use on injury severity and crash circumstances in skiers and snowboarders
. Hagel et.al
to eliminate confounding by the risk reduction of head and neck injuries from helmets that would bias the results against the risk reduction hypothesis - Rick
We used a matched case-control study over the November 2001 to April 2002 winter season. 3295 of 4667 injured skiers and snowboarders reporting to the ski patrol at 19 areas in Quebec with non-head, non-neck injuries [
] agreed to participate...Conditional logistic regression was used to relate each outcome to helmet use. There was no evidence that helmet use increased the risk of severe injury or high-energy crash circumstances. The results suggest that helmet use in skiing and snowboarding is not associated with riskier activities that lead to non-head-neck injuries
Helmets reduce the risk of head injury by as much as 60%, and there is evidence that they reduce the risk of neck injuries, as well. If there was some kind of operative risk "homeostat", those lower head and neck injury rates would be off-set by more frequent and/or more severe non-head-neck injuries, but nothing of the sort has occurred.
Perceived risk does affect behavior, that certainly seems true enough, but not in the way risk homeostasis hypothesis advocates would have us believe. Human behavior and risk-taking is far too complex to be explained by such simple-minded approaches.