Is Not Wearing A Bike Helmet As Stupid As Smoking Cigarettes?

(Update 12/2/2022. The skeptical cardiologist now wears a bike helmet.)

Several weeks after the skeptical cardiologist crashed his bicycle riding in Forest Park and experienced non-cardiac chest pain, he climbed back in the saddle again and rode the route that had resulted in his calamitous fall.

This time, I avoided the mysterious path less traveled.

As I approached  Washington University an elderly man riding a bike and wearing a bike helmet came up beside me. He was clearly very irritated by the fact that I was not wearing a bike helmet and kept gesticulating at his helmet to indicate that this was the proper choice of headgear.

I had, as is my usual practice, chosen not to wear a helmet and this man had taken it upon himself to nonverbally lecture me on what he perceived was inappropriately risky behavior.

As I continued my ride I began ruminating on my decision to engage in bike riding without a helmet and wondering if I was being like my patients who continue to smoke cigarettes despite my warnings of the health consequences of that behavior.

There can only be two reasons for an educated person not to wear a helmet:

1. S/he believes there is no or insufficient evidence that wearing a bike helmet will reduce their risk of serious head injury while riding.
2. S/he accepts that helmet-wearing reduces injury but is willing to accept this risk because not wearing the helmet is more pleasurable or convenient.

Similarly, my cigarette-smoking patients may either reject the (overwhelming) evidence of the dangers of this behavior or they may believe it is dangerous but feel that smoking is so pleasurable they decide to continue.

Not wearing a bike helmet lacks the addictive element that cigarette smoking contains but otherwise I think it is a reasonable analogy.

Do Bike Helmets Reduce Injury ?

Despite widespread public health advice to wear bike helmets, I have maintained that evidence for bike helmets reducing injury is lacking.

I’ve spent a fair amount of time since this gentleman upbraided me for being helmet-less reviewing the data again. I was prepared to regularly wear one if the data supported it. But it doesn’t.

A commonly cited statistic is that bike helmets reduce serious head injuries by 85% and brain injuries by 88%.  This comes from an observational study published in 1989 which has serious limitations and has never been reproduced. For an exhaustive critique of these data see here.

I think a fair summary is in this British Medical Journal editorial which is behind a paywall but can be reviewed as a PDF here (bmj-june-2013.pdfbicycle helmets and the law)

Cowritten by David Spiegelhalter, the Winton professor for the public understanding of risk at the London School of Hygiene, the editorial was commenting on a paper in the same issue which reported that a Canadian mandatory bike helmet law had minimal effect on cycling-related head injuries.

The writers note that this contradicts previous observational studies which have suggested a benefit from helmet wearing. Like all observational studies, these bike helmet studies are “vulnerable to many methodological shortcomings”:

  1.  If the controls are cyclists presenting with other injuries in the emergency department, then analyses are conditional on having an accident and therefore assume that wearing a helmet does not change the overall accident risk
  2. Observational studies cannot account for confounding variables that are unmeasured. For example, people who choose to wear bike helmets may be more cautious than those who don’t and so less likely to have a serious head injury regardless of wearing a helmet. (A 1997 study found that adolescents who smoked cigarettes were more likely to use smokeless tobacco, have multiple sexual partners, and not use bicycle helmets)

Many states and countries have passed laws mandating helmet-wearing but people who are forced by legislation to wear a bike helmet may wear it in a sloppy, ineffective manner. Their behavior may also change through “risk compensation” wherein they behave more irresponsibly in the belief that they are protected from injury.
A single study has also reported that car drivers give a larger clearance to cyclists without a helmet.

I have concluded that my not wearing a bike helmet is due to a lack of evidence to support the health consequences of that behavior. This happens to perfectly align with my disdain for bike helmets which chafe my forehead, make my head sweat and reduce my ability to hear (both charming and lethal) things.

Do Cigarettes Cause Death?

Cigarette smokers, on the other hand, can find no serious scientist or physician who is not convinced of the danger of this lethal habit because the scientific data are overwhelming. The CDC estimates cigarette smoking is responsible for 480,000 deaths per year and that it causes 90% of lung cancers and 80% of chronic obstructive lung disease. The only possible explanation for continuing is the element of addiction combined with the pleasure obtained from smoking.

Public Health Laws: Bike Helmets and Cigarette smoking

Australia and New Zealand are the only countries to have mandatory helmet laws. In the US, according to, bike helmets for youths are mandatory in 22 states.

In St. Louis County, they are mandatory for children under the age of 17. In some St. Louis municipalities (Creve Couer for one) they are mandatory for all age groups.

To date, there is no evidence that mandatory bike helmet laws reduce head injuries so why are they being passed?

On the other hand, the dangers of cigarette smoking are clear and there are no countries or states which make it illegal.

To those who would shame we non helmet wearers, I say: “Spend your time shaming those who smoke cigarettes.”

By the way, whenever public policy doesn’t seem to correspond to the evidence, we should look for bias and special interests.

It’s obvious in the world of tobacco that the bias and special interest toward allowing smoking comes from the tobacco industry.

In the cycling world, the bias and influence comes from the manufacturers of bike helmets.

Helmet free and loving it


N.B. As mentioned in the update of this 2017 post, the skeptical cardiologist has caved and wore a bike helmet on a regular bike yesterday (12/1/2022)


14 thoughts on “Is Not Wearing A Bike Helmet As Stupid As Smoking Cigarettes?”

  1. I’m always looking for an excuse not to wear a helmet – protection usually takes away from the natural enjoyment of any activity. Last year after the road on my commute was chip sealed, a car passing at high speed ejected a rock about the size of railroad ballast into my helmet. I was dazed and had to stop. Without a helmet I think it would have been a lot worse. The helmet doesn’t cover my entire face like my motorcycle helmet does, but it probably covers about half of my head. It claims to have some rotation-protection system. I think I’ll keep wearing it. Besides, my wife insists.

    • John,
      Thanks for sharing your story. I hadn’t previously considered random rocks flying towards my head as one of my cycling risks.
      I’m still riding my regular hybrid bike both in Encinitas and St. Louis without a helmet.
      However, I recently purchased an ebike, and (except when I forget) have worn a helmet with that. I think i read it was the law in CA for class 3 ebikes.
      We take risks, of course, every day. Just walking or jogging exposes us typically to cars running us over.
      I went into an American legion post last night crowded with people to watch my handyman play some Neil Young songs followed by an open comedy mic.
      Dr. P

  2. Twenty-eight years ago, on the eve before a glorious 8 day 600 mile “Pedal for Power” tour through Utah and a corner of Wyoming, my riding buddy and I were approaching a recessed in the roadway railroad crossing.
    I yelled up to him to remind him to cross it perpendicularly. He crossed both rails easily.
    After I made a quick front wheel turn to cross the first rail at 90 degrees, I was slammed to the ground by my less turned rear wheel seeking the depths of the recess around the rail.
    With a bleeding elbow, a bruised hip, and a broken handlebar mirror, we set off to the bike store to replace my broken (and compression reshaped) helmet.
    After a particularly stupid 50mph descent on rough road, I thought about how glad I was not to have needed to test that new helmet.
    In the time since, I tend to forego wearing a helmet when it is permissible. Through luck and increased caution, (and walking across all rail crossings), I have not had opportunity to be a statistic.
    Every automobile-bicycle accident in my area has resulted in a death, irrespective of the helmet, and even when the bicyclist was on the sidewalk!
    My opinion is “Kids:Yes, Adults:Choice”

  3. LISTEN TO THE OLD MAN!!!! Dave was in a bad bike wreck in which his helmet was cracked open. CRACKED OPEN. His head would have been had he not been sporting his light and aerodynamic helmet. Guess the Cruses know what they’re getting you for festivus. Not that you’d wear it. 😉 I subscribe to the idea that if helmets *might* help in *some* situations, that’s enough of a chance-improver for me to wear them proudly.

    • Lauren,
      I expect to see you wearing your helmet next time I see you walking down the street or driving your car since helmets might help in some situations encountered while engaging in those activities 🙂
      And I eagerly await your festivus gift which I shall employ as a planter.
      But seriously, take a look at this discussion which I extracted from the cycle site
      “The principal protection mechanism in a cycle helmet is the polystyrene foam, or styrofoam, that covers the head. When this receives a direct impact force, the styrofoam is intended to compress and in this way spread and reduce the force that is passed onto the skull, thus reducing linear accleration of the brain.
      However, it is common for helmets to break without the polystyrene foam compressing at all. A major helmet manufacturer collected damaged childrens’ helmets for investigation over several months. According to their senior engineer, in that time they did not see any helmet showing signs of crushing on the inside (Sundahl, 1998). Helmet foam does not ‘rebound’ after compression to any significant extent. If the styrofoam does not compress, it cannot reduce linear acceleration of the brain. The most protection that it can give to the wearer is to prevent focal damage of the skull and prevent minor wounds to the scalp. It is not likely to prevent serious brain injury.
      This helmet has split along the ventilation slots, which is common. However, the thickness of the styrofoam has not been compressed.
      It most likely gave no more than superficial protection.
      Some dissipation of impact force might occur from the action of a helmet breaking, but in most cases this is likely to be small. Helmet standards require the foam to start to compress at a level of force less than that which might be expected to lead to brain injury. While it is known that many helmets do not actually meet the standards to which they are supposed to be accredited (BHRF, 1081), it follows that if the styrofoam does not compress at all, the direct linear force on the helmet was minimal and it’s quite possible that the cyclist would not have received any injury if the helmet had not been worn.
      If the styrofoam is compressed, it still doesn’t prove that a helmet had a protective effect. This can be demonstrated with a fist and a brick wall.
      If you ‘shadow box’ at the wall but carefully stop your fist about 50 mm before it reaches the wall (be sure it’s limited by your arm’s length), no harm will come to your fist. If, without changing your position, you slip a 75 mm thick piece of styrofoam against the wall and repeat the punch, you’ll get compressed (and cracked) styrofoam and false ‘evidence’ that it saved you from harm. In other words, many impacts of helmets would be near misses with bare heads.
      In high impact crashes, such as most that involve motor vehicles or fixed objects like concrete barriers and lamp posts, the forces can be so great that a helmet will compress and break in around 1/1000th of a second. The absorption of the initial forces during this very short period of time is unlikely to make a sufficient difference to the likelihood of serious injury or death. It is for this reason that helmets contain stickers noting that no helmet can prevent all head injuries.
      Oblique impacts
      Cracks or tensile failure in helmets may be the result of a sideways or oblique, rather than linear, force on the helmet. Helmets are not tested nor certified for this kind of impact. However, if the impact occurs without any compression of the foam, it suggests that most of the force was parallel to the surface of the helmet and not directed towards the head. As the surface of a helmet is some small distance from the surface of the head, again the wearer may have suffered no injury at all if a helmet had not been worn.
      Rotational forces
      Most crashes leading to death or long-term disability involve rotational, or diffuse, forces. These differ from direct, or linear, forces in that it is insufficient to protect just the surface of the skull to prevent harm. It is necessary also to prevent the brain moving within the skull. Current cycle helmets are not designed to mitigate rotational forces and therefore offer very little protection against most life-threatening injuries (BHRF, 1039).
      The big picture
      It’s not a simple matter to draw conclusions about the benefit a broken or deformed helmet might have provided in a crash. However, the fact that serious injury to unhelmeted cyclists is as rare as helmet damage is common, suggests that most of the claims of benefit from damaged helmets are likely to be exaggerated.
      A better indication of the effectiveness of helmets comes from trends in fatal and serious injuries across whole populations of cyclists. Such data shows no reliable evidence from any jurisdiction that the risk of life-threatening injury has been reduced through the use of helmets.
      For example, in the state of Western Australia where bicycle helmets have been mandatory for all ages since July 1992, the annual cyclist death toll from 1987 to 1991 (pre-law) averaged 7.6 fatalities per year. From 1993 to 1997 (post-law) it was 6.4 fatalities per year, representing a 16% reduction (Meuleners, Gavin and Cercarelli, 2003). However, Government cycling surveys show cycling declined in Western Australia by approximately 30% during the 1990s following mandatory helmet law enforcement (WA, 1; WA, 2). Thus, relative to cycle use, fatalities went up, not down.
      National data from the United States (1991-2001) similarly shows lack of benefit (BHRF, 1041). A review of worldwide research for the UK Department for Transport found no statistically reliable evidence that cycle helmets had proved effective in reducing head injury (Hynd, Cuerden, Reid and Adams, 2009).
      There is a good deal of circumstantial evidence that helmeted cyclists are more likely to crash and in the process to damage their helmets. Data from one study (Wasserman et al, 1988) suggests that those wearing a helmet are more than 7 times likely to hit their (helmeted) heads than bare-headed cyclists, but this study may not be reliable due to the small numbers involved and self-reporting bias. Another study (Erke and Elvik, 2007) reports that helmet wearers have a 14% higher risk of injury per km cycled than those who do not wear helmets.
      Suspend belief
      The next time you see a broken helmet, suspend belief and do the most basic check – disregard the breakages and look to see if what’s left of the styrofoam has compressed. If it hasn’t, you can be reasonably sure that it hasn’t saved anyone’s life.”

  4. I know of at least two incidents where the helmet saved a person’s life or as a minimum major injuries. I always wear a helmet. Larry Mrazek

    • I think you have to take anecdotes of helmets saving lives with a grain of salt since you can never know what would happen if the individual had not been wearing a helmet.
      I often hear from patients who underwent an unnecessary stent or bypass (recommended not by me) that they believe it “saved their life”. However, based on my review of the data, I’m pretty sure it did not.
      For a really detailed discussion of this and the whole bike helmet safety issue check out the bike helmet safety research site page devoted to the question (

  5. Mandatory helmet laws would also seem to have a side effect of persuading at least some people not to get onto a bike in the first place, which seems like a poor policy outcome. We should be trying to make cycling easier to do, not creating additional barriers to it.

    • Exactly! Mandating helmets for bike riding stigmatizes the activity. Why don’t we mandate helmets for walking to the grocery store? Or driving in a car? or jogging? Plenty of people get hit by cars while jogging.

      • Mandates aside, not all helmets are made the same. Some are much less confining and sweaty than others. Ventilated; lightweight. Also, I think no one should assume that any helmet can protect from really serious damage like concussion or skull fracture. But think of all those hard things that can cut and gash: fire hydrants, metal road signs and stanchions, all those rear-view mirrors, mailboxes, road gravel. Take an ordinary spill without a helmet – nevermind over-the-handlebars – and you’re likely facing stitches… after the tweezers to get the gravel from next to the bone.
        Beyond it’s being a simple personal choice, those sans helmet mishaps are an expense. A few mattress stitches, a unit of blood, a few hours in ER will ultimately show up on the collective insurance premium.
        The guideline for walking at the edge of a road without sidewalk is to do it against traffic. You can see what’s coming, have time to decide, and avoid with a degree of agility. Cycling is with traffic. It reduces impact. Bikes are not nearly as agile as feet, so impact is more likely.
        But, you’ve decided. 🙂


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