from the world's big
The Bike Helmet Paradox
Recently a good friend told me over a pint in our local pub that he hadn't been able to sleep a wink for two nights. He'd been left traumatised by the sound of a skull cracking and the sight of brains spread over concrete. No, he hadn't just returned from fighting in Afghanistan, he'd witnessed one of the many cycling deaths that occur on the roads every year. We all have stories to tell about the wearing or not wearing of helmets and this is what makes the wearing of helmets such an emotive issue, which can blind us to the facts on both sides of the debate. I was subsequently intrigued to read a viral post on a friend's Facebook wall titled: "Why It Makes Sense To Bike Without A Helmet". The post currently has over 91,000 likes on Facebook, which I thought warranted it some investigation.
The author begins, like any good debater by outlining the very strong case for helmets:
"Let’s first get one thing out of the way: if you get into a serious accident, wearing a helmet will probably save your life. According to a 1989 study in the New England Journal of Medicine, riders with helmets had an 85% reduction in their risk of head injury and an 88% reduction in their risk of brain injury. That’s an overwhelming number that’s backed up study after study. Nearly every study of hospital admission rates, helmeted cyclists are far less likely to receive serious head and brain injuries. These studies confirm what we feel when we’re out for a spin on our bikes: We are exposed. Vulnerable. Needing of some level of protection."
After this good start, the author decides to take a "broader look at the statistics" by zoning in on one study of head injuries in San Diego in 1978. The author points out that only six percent of head injuries were amongst cyclists compared to 53% amongst drivers - seemingly oblivious to the fact that there would have been far more daily drivers than cyclists in San Diego in 1978, making the statistic more than a little misrepresentative. The author provides the pie chart on the left, which is considerably less impressive when placed alongside the pie chart on the right showing the rate at which American commuters actually cycle (the data on the right is from 2005 but the proportion of commuters cycling in the US has remained below 1% since the 70's).
Next the author points out that in the San Diego study and in another French study that was also not weighted for population: "more people were hospitalized after walking down the street than riding on a bicycle", a statistic that can likely be explained by the fact that while more or less everyone walks to some extent, relatively few people regularly cycle and old people tend to hurt themselves falling over a lot.
This is where things begin to get messy. The author cites a 1996 study which looks at injuries per hour travelled and suggests that motor vehicle occupants are actually slightly more likely to suffer head injury than cyclists. On the face of it, this is a shocking statistic, but considering the speed that cars travel, it is should perhaps not actually be surprising that cars may even be more dangerous to their occupants (and to others) than push bikes - and the suggestion that car drivers should wear helmets is certainly a compelling thought to say the least. Whether or not this is relevant information to whether cyclists should be singled out for wearing helmets is certainly an interesting topic for debate. In this respect, it is difficult to argue with the author who writes:
"In other words, if the reason we are supposed to wear helmets while biking is to prevent serious head injury on the off-chance we get into an accident, then why is it socially acceptable for pedestrians and drivers to go about bare-headed? Why has cycling been singled out as an activity in need of head protection?"
Things become yet more interesting when we scratch further beneath the surface. The author of the blog post writes:
"There's an important caveat to the results of that 1989 New England medical study: Bike helmets may reduce the risk of head and brain injury by 85-88%—but only for those who get into accidents.
If we take a closer look at the article we see that both the experiment and the control groups studied are those who have already been hospitalized for bike injuries. If one were to examine the medical and epidemiological literature on bike helmet effectiveness, you'll find the exact same condition over and over: Studies show that helmeted cyclists who are hospitalized are far less likely to have serious head trauma than bare-headed cyclists that have been hospitalized.
But wouldn't this be true, regardless of the activity? Logically, helmeted drivers should also receive significantly fewer head injuries than bare-headed drivers. Similarly, helmeted pedestrians should be less likely to receive serious head trauma than bare-headed ones. But such studies don't exist because there aren't enough helmeted drivers or pedestrians to make a comparison. In other words, one of the reasons we think helmeted cyclists are safer than unhelmeted ones may be due to availability of information more than actual levels of head safety.
Maybe that explains why there's no comparable fear of driving or walking without a helmet."
So the evidence remains clear that cyclists who wear helmets who have accidents are less likely to suffer brain injuries than cyclists that don't wear helmets that have accidents - which in my mind is evidence enough to more than justify wearing a helmet. The obvious next question is - are cyclists who wear helmets somehow more likely to get into accidents than cyclists who do not wear helmets - this is a complicated and fascinating debate, which we'll come back to later in this post. But this is not the case the author makes. The author takes the cognitive leap to suggesting that helmets in and of themselves might actually be harmful.
The author cites a New York Times article which reports an increase in bicycle head injuries during a time when helmet use became widespread which coincided with an overall decrease in cycling. There is an obvious correlation ≠ causation issue here which we could talk about all day from a great many different angles, so we'll begin by looking at the author's arguments one by one.
First, the author argues that "wearing a helmet changes how drivers perceive the cyclist" citing a study that suggests drivers pass closer to a cyclist wearing a helmet. The naturalistic study involving only one participant (who was also the experimenter) is interesting, but obviously potentially vulnerable to the same kind of conscious or unconscious bias that might lead a driver to drive closer to a cyclist. On its own it is not compelling evidence for the argument that one should not wear a helmet.
Next the author argues that "the design of the helmets themselves may increase the chance of some types of injuries when incidents do occur" linking to a meta-analysis but conveniently failing to mention what the meta-analysis actually found overall:
"In conclusion, the evidence is clear that bicycle helmets prevent serious injury and even death"
The author also failed to mention that the meta-analysis concluded that the supposed increase in (neck) injuries was found in old data and may not be applicable to the lighter helmets now in use. So that argument is also null and void - and a textbook example of cherry-picked data amongst a sea of data showing the precise opposite.
The author ends their case for the argument that helmets may be harmful with a crucial point which is worth thinking long and hard about if you are a cyclist:
"Finally, wearing a helmet may create a false sense of security and induce risk-taking that cyclists without head protection might not make. Those wearing helmets may take risks that they wouldn't otherwise take without head protection."
Due to the ethical problems that prevent researchers asking cyclists to ride with or without a helmet, this is a difficult hypothesis to test - but it certainly seems likely that wearing a helmet might lead cyclists to overcompensate by taking greater risks. It is worth reminding yourself that a helmet only provides limited protection even though it might lead some people to behave like they are invincible. If helmets really do make cyclists take greater risks then making their use obligatory presents an interesting public health conundrum. Is it possible that helmets could make people safer if they have an accident whilst simultaneously making them behave even more dangerously? It is next to impossible for us to know for sure if this is occurring due to the immense amount of additional uncontrollable variables in the equation.
The author of the blog post makes a number of good points but seems to have overstated the case. These arguments highlight the fact that when it comes to human behaviour, epidemiological data gets incredibly messy and it is can be all too easy to intentionally or not, make whatever argument we want based on what data we look for. We've not even touched on the possibility that the type of casual cyclist who chooses not to wear a helmet may already behave very differently to the type of cyclist who does choose to wear a helmet. As Ben Goldacre explained in an editorial on bike helmets in the British Medical Journal, we are dealing with "confounding variables that are generally unmeasured and perhaps even unmeasurable."
What we are left with is a paradox. On an individual level it is clear that helmets can and do save cyclists from serious head injury and death provided that cyclists and the drivers around them don't overcompensate by taking greater risks. On a societal level, it seems that laws enforcing helmet use have done nothing to make cyclists safer and have driven a great many casual cyclists off the road - which as the author of the post rightly points out, indirectly increases the danger to cyclists in the long run, as cyclists are protected by strength in numbers. Furthermore, in places where helmet requirements have driven cyclists off the road it has been argued that the negative effects on public health outweigh any possible benefits in prevented injuries. In Australia, when a helmet law was introduced at a time when the popularity of cycling was on the rise, a 44% decrease in children cycling was observed, which was five times the size of the increase in children wearing helmets. According to a paper published in the BMJ, it would take "at least 8000 years of average cycling to produce one clinically severe head injury and 22,000 years for one death". It has also been estimated that the health benefits of cycling outweigh the life-years lost by a factor of twenty to one.
The whole argument reminded me of an anecdote regarding the introduction of helmets for soldiers in WW1 and the supposed consequent increase in recorded head injuries. As the story goes, generals nearly recalled the helmets before it was realised that the rise in head injuries could be explained by injuries that before the introduction of helmets would have been recorded as deaths. I've been unable to track down a bona fide citation for this anecdote amongst the many repetitions of it online (but I've not found any attempts to disconfirm it either). In any case, this has certainly not been true for bike helmets - where deaths still make up a tiny fraction of outcomes from bike accidents, but it is an interesting demonstration of how statistics can mislead - something that seems to be going on left, right and centre in the bike helmet debate.
After looking at the evidence, I'm happy to conclude that I'll choose to wear a helmet, but I'll not be beating the drum that cyclists should be forced to wear helmets - as the health benefits of cycling with or without a helmet are so great, that the risks of riding with or without a helmet pale in comparison. The evidence paradoxically seems to show that while wearing helmets does make cyclists safer, helmet laws don't make cyclists safer and actually harm public health in the long run.
Attewell R.G., Glase K. & McFadden M. Bicycle helmet efficacy: a meta-analysis., Accident; analysis and prevention, PMID: 11235796
Goldacre B. & Spiegelhalter D. (2013). Bicycle helmets and the law., BMJ (Clinical research ed.), PMID: 23760970
Robinson D. (1996). Head injuries and bicycle helmet laws, Accident Analysis & Prevention, 28 (4) 463-475. (PDF)
Walker I. (2006). Drivers overtaking bicyclists: objective data on the effects of riding position, helmet use, vehicle type and apparent gender., Accident; analysis and prevention, PMID: 17064655
Wardlaw M.J. Three lessons for a better cycling future., BMJ (Clinical research ed.), PMID: 11124188
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Richard Feynman once asked a silly question. Two MIT students just answered it.
Here's a fun experiment to try. Go to your pantry and see if you have a box of spaghetti. If you do, take out a noodle. Grab both ends of it and bend it until it breaks in half. How many pieces did it break into? If you got two large pieces and at least one small piece you're not alone.
But science loves a good challenge<p>The mystery remained unsolved until 2005, when French scientists <a href="http://www.lmm.jussieu.fr/~audoly/" target="_blank">Basile Audoly</a> and <a href="http://www.lmm.jussieu.fr/~neukirch/" target="_blank">Sebastien Neukirch </a>won an <a href="https://www.improbable.com/ig/" target="_blank">Ig Nobel Prize</a>, an award given to scientists for real work which is of a less serious nature than the discoveries that win Nobel prizes, for finally determining why this happens. <a href="http://www.lmm.jussieu.fr/spaghetti/audoly_neukirch_fragmentation.pdf" target="_blank">Their paper describing the effect is wonderfully funny to read</a>, as it takes such a banal issue so seriously. </p><p>They demonstrated that when a rod is bent past a certain point, such as when spaghetti is snapped in half by bending it at the ends, a "snapback effect" is created. This causes energy to reverberate from the initial break to other parts of the rod, often leading to a second break elsewhere.</p><p>While this settled the issue of <em>why </em>spaghetti noodles break into three or more pieces, it didn't establish if they always had to break this way. The question of if the snapback could be regulated remained unsettled.</p>
Physicists, being themselves, immediately wanted to try and break pasta into two pieces using this info<p><a href="https://roheiss.wordpress.com/fun/" target="_blank">Ronald Heisser</a> and <a href="https://math.mit.edu/directory/profile.php?pid=1787" target="_blank">Vishal Patil</a>, two graduate students currently at Cornell and MIT respectively, read about Feynman's night of noodle snapping in class and were inspired to try and find what could be done to make sure the pasta always broke in two.</p><p><a href="http://news.mit.edu/2018/mit-mathematicians-solve-age-old-spaghetti-mystery-0813" target="_blank">By placing the noodles in a special machine</a> built for the task and recording the bending with a high-powered camera, the young scientists were able to observe in extreme detail exactly what each change in their snapping method did to the pasta. After breaking more than 500 noodles, they found the solution.</p>
The apparatus the MIT researchers built specifically for the task of snapping hundreds of spaghetti sticks.
(Courtesy of the researchers)
What possible application could this have?<p>The snapback effect is not limited to uncooked pasta noodles and can be applied to rods of all sorts. The discovery of how to cleanly break them in two could be applied to future engineering projects.</p><p>Likewise, knowing how things fragment and fail is always handy to know when you're trying to build things. Carbon Nanotubes, <a href="https://bigthink.com/ideafeed/carbon-nanotube-space-elevator" target="_self">super strong cylinders often hailed as the building material of the future</a>, are also rods which can be better understood thanks to this odd experiment.</p><p>Sometimes big discoveries can be inspired by silly questions. If it hadn't been for Richard Feynman bending noodles seventy years ago, we wouldn't know what we know now about how energy is dispersed through rods and how to control their fracturing. While not all silly questions will lead to such a significant discovery, they can all help us learn.</p>
Join Pulitzer Prize-winning reporter and best-selling author Charles Duhigg as he interviews Victoria Montgomery Brown, co-founder and CEO of Big Think.
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In a recent study, researchers examined how Christian nationalism is affecting the U.S. response to the COVID-19 pandemic.
- A new study used survey data to examine the interplay between Christian nationalism and incautious behaviors during the COVID-19 pandemic.
- The researchers defined Christian nationalism as "an ideology that idealizes and advocates a fusion of American civic life with a particular type of Christian identity and culture."
- The results showed that Christian nationalism was the leading predictor that Americans engaged in incautious behavior.
A pastor at the chapel of the St. Josef Hospital on April 1, 2020 in Bochum, German
Sascha Schuermann/Getty Images<p>Christian nationalists, in general, believe the U.S. and God's will are tied together, and they want the government to embody conservative Christian values and symbols. As such, they also believe the nation's fate depends on how closely it adheres to Christianity.</p><p style="margin-left: 20px;">"Unsurprisingly then, in the midst of the COVID‐19 pandemic, conservative pastors prophesied God's protection over the nation, citing America's righteous support for President Trump and the prolife agenda," the researchers write.</p><p style="margin-left: 20px;">"Correspondingly, the link between Christian nationalism and God's influence on how COVID‐19 impacts America can be seen in proclamations about God's divine judgment for its immorality―with the logic being that God is using the pandemic to draw wayward America <em>back </em>to himself, which assumes the two belong together."</p><p>The logical conclusion to this kind of thinking: America can save itself not through cautionary measures, like mask-wearing, but through devotion to God. What's more, it stands to reason that Christian nationalists are less likely to trust the media and scientists, given that these sources are generally not concerned with promoting a conservative, religious view of the world.</p><p>(The researchers note that they're unaware of any research directly linking Christian nationalism to distrust of media sources, but that they're almost certain the two are connected.)</p>
Predicted values of Americans' frequency of incautious behaviors during the COVID‐19 pandemic across values of Christian nationalism
Perry et al.<p>In the new study, the researchers examined three waves of results from the Public and Discourse Ethics Survey. One wave of the survey was issued in May, and it asked respondents to rate how often they engaged in both incautious and precautionary behaviors.</p><p>Incautious behaviors included things like "ate inside a restaurant" and "went shopping for nonessential items," while precautionary behaviors included "washed my hands more often than typical" and "wore a mask in public."</p><p>To measure Christian nationalism, the researchers asked respondents to rate how strongly they agree with statements like "the federal government should advocate Christian values" and "the success of the United States is part of God's plan."</p><p>The results suggest that, compared to other groups, Christian nationalists are far less likely to wear masks, socially distance and take other precautionary measures amid the COVID-19 pandemic.</p><p style="margin-left: 20px;">"Christian nationalism was the leading predictor that Americans engaged in incautious behavior during the pandemic, and the second leading predictor that Americans avoided taking precautionary measures."</p><p>But that's not to say that religious beliefs are causing Americans to reject mask-wearing or social distancing. In fact, when the study accounted for Christian nationalist beliefs, the results showed that Americans with high levels of religiosity were likely to take precautionary measures for COVID-19.</p>
Limitations<p>Still, the researchers note that they're theorizing about the connections between Christian nationalism and COVID-19 behaviors, not documenting them directly. What's more, they suggest that certain experiences — such as having a family member that contracts COVID-19 — might change a Christian nationalist's behaviors during the pandemic.</p><p style="margin-left: 20px;">"Limitations notwithstanding, the implications of this study are important for understanding Americans' curious inability to quickly implement informed and reasonable strategies to overcome the threat of COVID‐19, an inability that has likely cost thousands of lives," they write.</p>
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