Okay, I'll bite.
I'll try to discuss mostly about the actual evidence base and will provide access to the source literature (rather than secondhand reports or abstracts). I have put them in my shared folder in Google Docs since some of these articles are not available (for free) for the general public. I would ask that members to try not to debate or question aspects of the articles based purely on abstracts; but rather, to actually read the relevant article in its entirety first.(1) Does wearing a bicycle helmet reduce the likelihood of head injury, compared to not wearing a helmet for the individual?
This is probably the only question where we have an answer that is supported by good evidence. The answer is yes
. The Cochrane Database of Systematic Reviews
has published a meta-analysis
of some good quality case control studies
. There are no randomised control trials
(considered the gold standard) comparing helmets to no helmets. However, I can't imagine an RCT design into this question that would be considered ethical in humans so it is unlikely that there ever will be one.
The article contains a "plain language summary" that is below verbatim:
Reference: Thompson DC, Rivara F, Thompson R. Helmets for preventing head and facial injuries in bicyclists. Cochrane Database of Systematic Reviews 1999, Issue 4. Art. No.: CD001855.(2) Do mandatory bicycling helmet laws reduce the rate of head injury, compared to voluntary helmet wearing?
Wearing a helmet dramatically reduces the risk of head and facial injuries for bicyclists involved in a crash, even if it involves a motor vehicle
Cycling is a healthy and popular activity for people of all ages. Crashes involving bicyclists are, however, common and often involve motor vehicles. Head injuries are responsible for around three-quarters of deaths among bicyclists involved in crashes. Facial injuries are also common. The review found that wearing a helmet reduced the risk of head or brain injury by approximately two-thirds or more, regardless of whether the crash involved a motor vehicle. Injuries to the mid and upper face were also markedly reduced, although helmets did not prevent lower facial injuries.
The evidence to the answer to this question is somewhat less clear but it is "probably yes". It is a contested viewpoint, however. Public health physicians tend to agree in the affirmative (i.e., the laws do reduce the rate of head injury for bicyclists) and there are a few notable dissenters (e.g., Australian statistician Dorothy Robinson) who bring up some compelling weaknesses in the usual interpretation of the data.
The British Medical Journal
in 2006 published an analysis from Robinson and a rebuttal from Hegel. Interesting quotation from Robinson:
Safety in numbers
Injuries to cyclists follow a clear â€œsafety in numbersâ€ relation; injury rates per cyclist are lower when more people cycle. Data for cyclists in collisions with motor vehicles show helmet laws increased the risk of death or serious head injury relative to the risk for pedestrians and the amount of cycling. This implies helmet laws are counterproductive.
Collisions with motor vehicles cause nearly all deaths and debilitating head injuries among cyclists. A UK emergency department study found that such collisions caused 58% of head injuries to adult cyclists and 50% of all head injuries to cyclists. The large benefits from the road safety campaigns should be contrasted with the lack of obvious effect on head injuries from helmet laws.
Significant point of rebuttal from Hegel and colleagues:
Robinsonâ€™s opposition to helmet laws is contrary to published evidence on the effectiveness of bicycle helmets. At least six independent studies have reported a protective association between wearing bicycle helmets and head injuries. Furthermore, systematic reviews of the relation have all noted a protective effect of helmets. Similarly, six studies have examined the relation between helmet laws and head injuries, and all found a reduction in head injuries after legislation was enacted.
Link to both articles here (one follows the other): https://docs.google.com/leaf?id=0Bw8CaK ... ist&num=50
Robinson D. Do enforced bicycle helmet laws improve public health? BMJ 2006;332:722â€“5
Hagel B., Macpherson A., Rivara F., Pless B. Arguments against helmet legislation are flawed. BMJ 2006;332:725â€“6
The Cochrane Database of Systematic Review also has a review on this question. It answers in the affirmative as well but there are some caveats that are noted that I will discuss later. The plain language summary follows:
Bicycle helmet legislation for the uptake of helmet use and prevention of head injuries
Cycling is a popular past-time among children and adults and is highly beneficial as a means of transport and obtaining exercise. However, cycling related injuries are common and can be severe, particularly injuries to the head.
Bicycle helmets have been advocated as a means of reducing the severity of head injuries, however voluntary use of helmets is low among the general population. Bicycle helmet laws mandating their use have thus been implemented in a number of jurisdictions word-wide in order to increase helmet use. These laws have proved to be controversial with opponents arguing that the laws may dissuade people from cycling or may result in greater injury rates among cyclists due to risk compensation. This review searched for the best evidence to investigate what effect bicycle helmet laws have had. There were no randomised controlled trials found, however five studies with a contemporary control were located that looked at bicycle related head injury or bicycle helmet use. The results of these studies indicated a positive effect of bicycle helmet laws for increasing helmet use and reducing head injuries in the target population compared to controls (either jurisdictions without helmet laws or non-target populations). None of the included studies measured actual bicycle use so it was not possible to evaluate the claim that fewer individuals were cycling due to the implementation of the helmet laws. Although the results of the review support bicycle helmet legislation for reducing head injuries, the evidence is currently insufficient to either support or negate the claims of bicycle helmet opponents that helmet laws may discourage cycling.
: Macpherson A, Spinks A. Bicycle helmet legislation for the uptake of helmet use and prevention of head injuries. Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD005401.
Basically, one of the key criticisms is that we are using the wrong measurement and/or interpreting it incorrectly. For instance, a drop in the rate of head injuries after introduction of laws could be due to an associated third variable (e.g., drop in ridership). Or, that head injury rates are too narrow to capture to health consequences of the law (e.g., the increased rates of death and serious injuries in collisions with cars after the introduction of the law).(3) Are mandatory bicycling helmet laws cost-effective?
Another issue that is important from a public health perspective is not just whether the intervention (in this case, helmet laws) achieve their goal (reducing head injury rates in bicyclists), but whether it is worthwhile
. In part, this discussion has been raised from time to time on this forum in a rhetorical fashion. Various posters have asked whether car passengers should wear helmets, or even pedestrians. It is probable that enforcing helmets in these groups would also reduce the rate of head injury, particular car passengers. To me, this question is the one that is often smeared into the background in emotive debates but is probably the most important one. It is not enough that a particular intervention has an effect but rather, whether it is an important enough effect
that it should be mandated. Unfortunately, debaters have usually put themselves into a dogmatic position before this question can be evaluated dispassionately.
The answer to whether helmet laws are cost-effective is most likely no
, even without taking into account further negative externalities
An cost-benefit analysis of the New Zealand helmet laws (focusing only on the cost of helmets and the cost/savings head injuries) found the following:
Reference: Taylor M., Scuffham P. New Zealand bicycle helmet law - do the costs outweigh the benefits? Injury Prevention 2002;8:317â€“320
The HWL (helmet wearing law) was cost saving in the youngest age group but large costs from the law were
imposed on adult (>19 years) cyclists.
Although helmets are likely to make a difference to head injuries both at an individual level and probably at a legislative level on the community, the actual rates of head injury from cycling is very low.
Piet De Jong an actuary has published an article looking at the health impacts of mandatory bicycle helmet laws. He addresses this question with what he calls a "simple" model. The abstract from his article:
Reference: De Jong, Piet, The Health Impact of Mandatory Bicycle Helmet Laws (February 24, 2010). Available at SSRN: http://ssrn.com/abstract=1368064 The question of ridership
This article seeks to answer the question whether mandatory bicycle helmet laws deliver a net societal health benefit. The question is addressed using a simple model. The model recognizes a single health benefit -- reduced head injuries, and a single health cost -- reduced cycling.
Using estimates suggested in the literature of the effectiveness of helmets, the health benefits of cycling, head injury rates, and reductions in cycling, leads to the following conclusions. In jurisdictions where cycling is safe, a helmet law is likely to have a large unintended negative health consequence. In jurisdiction where cycling is relatively unsafe, helmets will do little to make it safer and a helmet law, under relatively extreme assumptions may make a small positive contribution to net societal health. As such, helmet legislation appears to be a distraction from the main bicycle related health issue: the safety of the bicycling environment. The model serves to focus the mandatory bicycle helmet law debate on overall health. The methodology developed in this article is can be used in other situations where safety initiatives are proposed for healthy activities.
I won't specifically discuss this in this post. The Canadian study brought up by cobbler I discussed previously: viewtopic.php?p=457439#p457439
(can access full text of the article) viewtopic.php?p=457461#p457461 viewtopic.php?p=458564#p458564
Fixed citation error[/edit]