Because you are analysing the wrong data.
A helmet cannot prevent an accident occuring. There's no reason to think it would.
If you measure by that standard, then it's easy to prove that helmets have no effect.
However, the vast body of research out there shows that helmets DO help to reduce the severity of head injury.
If we measure by that standard - then enforced legislation starts to look downright common sense - which is of course why anti-helmet advocates refuse to acknowledge that data.
Few of us are anti-helmet advocates. We just want governments and local authorities to stop promoting them in lieu of real change. My biggest problem with all of this is that even if helmets help (they seem to in a few circumstances), the chances of a helmet making any difference to an individual are tiny, and their importance is blown all out of proportion. They have become the biggest red herring known to road safety.
That said, there is no vast body of studies showing a significant benefit. There are a number of studies showing a small benefit. There are a few discredited studies showing a significant benefit, there are a few studies that show cyclists who wear helmets may take more risks, and there is a vast body of stuff that doesn't really tell us much at all.
There are a number of problems with this study, all very ably analysed by cyclehelmets.org https://www.cyclehelmets.org/1136.htmlpoetd wrote:https://www.sciencedirect.com/science/a ... 7587900029
Analysis of the crude, unadjusted data showed a statistically significant association between helmet use and reduced severity of head injury
The actual research is neither presented nor linked to in this article. The author does not credit the researchers nor tell us where to find the study.poetd wrote:https://uk.reuters.com/article/us-healt ... KKCN10U1LY
Researchers found that people wearing helmets had 52 percent lower risk of severe TBI, compared to unhelmeted riders, and a 44 percent lower risk of death.
Riders with helmets also had 31 percent lower odds of facial fractures. The upper part of the face, particularly around the eyes, was most protected
This study includes motorcycle and ATV use, without separating out bicycle helmets. It also noted that there is an association between alcohol use and not wearing a helmet, but does not correct for the resultant bias. Furthermore, this study refers to a study by Thompson, Rivara, et al that the authors subsequently admitted contained significant problems with the methods.poetd wrote:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3800611/
These data demonstrate that lack of helmet use is significantly correlated with abnormal head CT scans (fractures), admission to the hospital, admission to the ICU, and overall worse TBI severity both in the prehospital and ED environments
This study is does demonstrate some benefits of helmet use among children who have crashed or been crashed into. You may have missed that it also shows an slight increase in head injuries among those who are 16 - 65 years old. Admittedly, the difference is not significant when a motor vehicle is involved. Nor is it significant for those over 65. That occurred despite a decrease in adult bicycle usage. Also, the study admits some difficulties in understanding bicycle usage among children.poetd wrote:https://academic.oup.com/heapro/article/22/3/191/598707
Most bicycle-related accidents with head injuries (70%) happen without the involvement of motor vehicles (single accidents), but this study shows a decrease in head injuries also in collisions with motor vehicles. It also shows a decrease in both concussion and skull fracture.
It seems very strange to me that they published a study in 2007 using data that was more than a decade old. Especially since the data collected by the road traffic authority in Sweden is very much better from 2000 onwards than in the period for which they took data.
poetd wrote:https://www.abc.net.au/science/articles ... 751304.htm
The team found cyclists without helmets were 5.6 times more likely to suffer any head injury than cyclists wearing a helmet and 5.5 times more likely to suffer a severe head injury.
So it's not like the benefits aren't measured and known, you're just chosing to ignore them in favour of other cherry-picked data which supports your position.
Again, this is a study of those admitted to hospital, which says nothing about those who were not admitted (and also is not corrected for alcohol use or other factors). For Australia, we *know* that crash rates for cyclists increased with the introduction of a law requiring mandatory helmet use. There was an estimated 14% increase in accident risk per kilometer cycling, and a steady increase in the hospital admissions for cyclists. Yet, a study which demonstrates that a handful of cyclists had less severe injuries, shows benefits?
I don't think that I am the one one cherry-picking data.