do bike helmets work?

I was curious if bike helmets protect bicycle riders from injuries to the head, and the answer in the epidemiology literature is “yes.”  If that is all you are interested in, then read no further. Jk.  Actually the topic is quite nuanced and has a lot of different interest groups besides just cyclists- groups like helmet companies, government, and public health researchers and clinicians.

One thing I found is that more studies on bike injuries are needed. It appears that the critical question of helmet vs. no helmet has been answered, but big gaps in research still remain about the safety of specific helmet designs (shape, fitted vs. ill fitted, specific materials and failure rates), differences in driver behavior towards helmet wearers, the psychology of wearing a helmet, and policy decisions about  legislated vs. non-legesated helmet use.  Even simple surveys of helmet use are lacking.  Many times helmet data is not collected after traffic accidents- such as NYC with “only 1/3 of 1037 serious injury crashes from 2001-2003 was helmet use recorded” (pdf).


Do helmets work?

It is known with some confidence that helmet use greatly reduces the risk of bicycle-related head injuries

      What is the risk of injury?

      One study estimated that children <17 iu urban areas have serious bike related accidents at a rate of 37.4 in 100,000 (article).  I could not find a rate for adults or all riders.

      What are risk factors for bicycle injuries (article):

      • Cyclist is male.
      • Cyclist is nine to 14 years of age.
      • Cycling in the summer.
      • Cycling in late afternoon or early evening.
      • Cyclist does not wear helmet.
      • Motor vehicle involved.
      • Unsafe riding environment.
      • Cyclist is from an unstable family environment.
      • Cyclist has preexisting psychiatric condition.
      • Cyclist is intoxicated.
      • Cyclist is involved in competitive mountain-bike racing.

      I have a few risks to add myself:

      • talking on a cellphone (driver or biker)
      • near an intersection
      • deaths by collision with a large vehicle
      • helmet type/shape (data not collected on round vs. aerodynamic helmets, but there is research that shows that aero helmets cause more neck strain in sideways/rolling falls)
      • helmet fit (article)
      • defective or not maintained parts. I see people all the time with dangerously bad breaks and handlebars. Either by ignorance or laziness these problems persist. One way to tell is somebody’s bike is not in good shape is to look for little things that are not dangerous problems, like unraveling handlebar tape, but could indicate general neglect.
      • on an arterial street or highway

      Are you still not convinced?

      Bicycle helmet companies and bike activists won’t say this, but if you absolutely don’t want to wear a helmet there are other ways to reduce your risk of major injuries while riding. These involve reducing other risks associated with injuries, such as from the list above. Best best are to ride on secondary roads with slow traffic, good lighting, few intersections, and wide lanes. Ride with a friend to be more visible and better at clogging up the right lane. Another speculative idea is to bike with a mild wobble to cause cars to give a wide berth.


      19 responses to “do bike helmets work?

      1. Excellent review of a very important issue.
        However, as a parent and prior ER physician I cannot advise not wearing a helmet under any conditions. Head injuries can occur in your driveway.

      2. What helmet(s) do you think are safest?

      3. Bell makes a round helmet with almost no air vents, which gives more foam and because of the shape it won’t snap your neck if you slide on the pavement.

      4. Richard Keatinge

        Actually the best epidemiology says that helmets probably don’t work, laws have stopped a lot of people cycling and have done nothing for head injury rates, see It appears that helmets break easily, but don’t absorb the impact, see the engineers quoted at A broken helmet has simply failed. Helmets have also strangled some young children who were wearing helmets while playing off their bicycles. At my moderately advanced age it’s far too dangerous not to cycle – regular cycling, Danish style, not too far, not too fast, nearly halves the death rate, see All-Cause Mortality Associated With Physical Activity During Leisure Time, Work, Sports, and Cycling to Work. Andersen et al, Arch Intern Med. 2000;160:1621-1628.

        • Richard, thanks for your comment. This is a good reminder that there are people on both sides of this issue. My friend also points out that helmets change your sense of balance and may make it harder to recover from a skid.
          Would you mind sending me the pdf of the BMJ epi article you cite. I don’t have access to it.

      5. Helmet always work. It’s like saying, does seatbelt work? of course it does..If you hit your head on the floor without helmet, what happen to your head?

      6. The style of writing is quite familiar to me. Did you write guest posts for other bloggers?

      7. I think the issue is much more complicated. The article cited for the fact that 63-88% of head injuries are prevented by helmets is a review article, not a study. I have read many articles that say these reviews are skewed one way or another, or should be discredited for one reason or other.

        The problem is there is not enough data to say either way. From recently shopping for a bike helmet, I can say that they do not deform like ski helmets do, and I find the critisms relating to the structure to be compelling (non-deforming, and risk of rotational injuries, which may be more severe than what would have occurred had one not been wearing a helmet).

        I would definitely wear a helmet if I knew it was not going to increase my risk of injury. As of right now, I think the jury is out, and I think the designs will progress since they are relatively new with regard to pro racing.

      8. I agree most helmets are built w/ looks in mind first, and safety second. The new “city” helmets that look like skateboard helmets do seem appealing for reducing rotational injuries. Some around Berkeley, CA (1%) are commuting in bmx helmets to reduce jaw injuries.

        My own personal opinion is formed from hearing about major head injuries of people who weren’t wearing helmets. My cousin crashed on his own- and without a helmet- and got a bad concussion that left him sick for several days. He admits it was preventable w/ a helmet. He fell back on his head, right where a helmet would work.

      9. Where do I find SHOEI Helmets in Singapore that have PSB Certification?

      10. ” bike with a mild wobble to cause cars to give a wide berth.” lol
        it’s an idea…

      11. “My cousin crashed on his own- and without a helmet- and got a bad concussion that left him sick for several days. He admits it was preventable w/ a helmet. He fell back on his head, right where a helmet would work.”

        This is an anecdote, and this is why you do studies. If he had been wearing a helmet you could say the exact same story with the punchline “the helmet saved his life”. Both are near to worthless as evidence.

        Ask a helmet campaigner what happened to the 85% drop in fatalaties predicted by the early- but flawed – studies. They will first triumph the reduction until it is pointed out that when reduction in cycling is taken into account fatalties per cyclist have increased!

        Fact: the best studies (which for technical reasons are the NEw Zealand ones published by Scuffham) showed almost no effect from a 95% increase in bike helmet use.

      12. I realize I’m commenting on an old post, but it’s still relevant. Particularly with the rash of concussions and, unfortunately, one death from head injuries in the pro peloton (grand tours) this year (2011)–yes, those wearing top quality helmets–I think it is something that needs to be examined further.

        Motorcyclists have the debate frequently about whether helmets save lives. Insurance companies have data, but some riders have their own opinions. But what arguably saves some motorcyclists is a much more robust helmet with much more coverage than the skull cap coverage of an average road bicycle helmet. Bicycle helmets may be light weight and still prevent some injuries from impact on the top and, to some extent, the side and back, but there is zero protection for the face.

        I wonder if any studies have been done on the frequency and severity of different impact zones of the head for bicycle riders. Here’s a study for motorcyclists:

        You might notice that the top of the head–what is the most protected area on a roadie bicycle helmet–is near the bottom in actual incidence percentage–whereas the sides and particularly the face, back, and chin area are much more likely to be impacted. Yet, those areas are less protected, if at all, by bicycle helmets. Furthermore, chin straps are very critical in keeping a helmet in place to do its job. I find that bicycle helmet straps are not very good at this, as evidenced by many I see worn loosely. I wonder about studies on straps, too.

      13. How much will it cost to send this letter to ? underage tube

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