Do bicycle safety helmets reduce severity of head injury in real crashes?

Dorsch MM, Woodward AJ, Somers RL. Accident Analysis and Prevention: 1987 Jun;19(3):183-90 .
An earlier version of this paper was presented to the 28th Annual Conference of the American Association for Automotive Medicine, October 1984.

Summary of paper (based on authors' abstract)

894 South Australian bicycling enthusiasts returned mail questionnaires about their most recent bicycle crash and their helmet use at the time. 197 bicyclists reported a crash within the past five years in which they had struck their head or helmet. 75 of these bicyclists did not wear a helmet; most others wore a hairnet-style racing helmet and others a hard shell helmet. Analysis of the crude, unadjusted data showed a statistically significant association between helmet use and reduced severity of head injury. Also the risk of death from head injury was considerably reduced for helmeted bicyclists.

BHRF Commentary

This cohort study was conducted in the early 1980s at a time when very few cyclists were wearing helmets. The majority of helmets worn were of the hairnet type, not modern cycling helmets. It was found that 62% of those who had hit their heads wore helmets. The paper didn't report helmet wearing rates of cyclists who didn't crash, or those who didn't hit their heads. However, the remarkably high percentage of cyclists hitting their heads who wore helmets might be an indication that helmet wearers may hit their heads more frequently than non-wearers.

The study did not involve fatalities; the most serious injuries were 1 cyclist with a skull fracture and 6 cyclists with concussion lasting more than 1 hour (3 of whom wore helmets, with 2 non wearers and 1 wearer having concussion lasting more than 24 hours). Nonetheless, the authors used an unpublished (and hence unverifiable) method to roughly estimate the efficacy of bicycle helmets in saving lives, suggesting that 90% of deaths could be prevented by good hard helmets, 80% by hairnet helmets and 70% by poor, hard helmets.

An Australian Federal Parliamentary inquiry of 1985 cited that estimate, but in her own evidence to the inquiry, Dr Dorsch retreated from it, saying: "One has to be very careful in making estimates of how effective universal bicycle helmet wearing would be in reducing deaths and serious injuries. ... people who are wearing what we regarded as the good, hard helmet ... had 19 times less risk of suffering a fatal head injury. That was a hypothetical procedure. ... it was based largely on an adult group of cyclists and because we went through a rather hypothetical statistical procedure to arrive at those numbers, I think one would have to be very careful in making estimates of how effective universal bicycle helmet usage would be in reducing deaths and serious injuries. In our paper we did, sure, put estimates on it but as a very hypothetical procedure. I was a bit distressed by some of the reports I had seen that suggested that 75 per cent of deaths could be prevented by everyone wearing very good, hard helmets." (HoRSCTS, 1985)

Sage, Cairns, Koelmeyer and Smeeton, 1985 , commenting on the 1984 version of the paper, stated with regard to the study that: "Injuries of fatal severity to multiple organ systems were seen in sixteen of the twenty riders, including six with no significant head injury. Only four riders died of fatal injury to the head alone and one of these was the only rider know to be wearing a safety helmet. His death resulted from a fall from a bike at moderate speed rather than collision with a motor vehicle".

Towner et al, 2002b noted a number of limitations of this paper. Helmet use and type of injury were self-reported and thus a potential source of bias. The study was restricted to cycling enthusiasts with a high rate of voluntary helmet use, who were likely to be very different in their skills and exposure to the general population. 85% of the sample were males. The use of an unpublished method meant that no conclusion could be drawn about the ability of helmets to reduce deaths.

Conclusion

This early study, based on a small sample with biases acknowledged by its authors, has not stood the test of time for its predictions have not been borne out by subsequent real-world experience.

References

HoRSCTS, 1985

House of Representatives Standing Committee on Transport Safety, June 1985. Dr Dorsch's evidence, given in a personal capacity, is on page 916A of the transcript.

Sage, Cairns, Koelmeyer and Smeeton, 1985

Sage MD, Cairns FJ, Koelmeyer TD, Smeeton WMI, 1985. Fatal injuries to bicycle riders in Auckland. NZ Med J Vol 98, No793, pp1073-1074, 1985.

Towner et al, 2002b

Towner E, Dowswell T, Burkes M, Dickinson H, Towner J, Hayes M, 2002. Bicycle helmets - a review of their effectiveness: a critical review of the literature – Technical Annexe. Department for Transport RSRR30 Annexe.