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The effectiveness of bicycle helmets: a study of 1710 casualties
McDermott FT, Lane JC, Brazenore GA, Debney EA. Journal of Trauma, 1993; 34(6):834-845.
Summary of paper (from authors' abstract)
Helmeted cyclists had more serious non-head injuries (neck and extremities/pelvic girdle) than bareheaded cyclists. Non-approved helmets offered no significant protection against head injuries. This paper does not provide reliable evidence that helmets reduce head injuries.
By Towner et al, 2002:
- Half of the sample had no impact.
- It is difficult to interpret some of the comparisons.
- Increased risk of neck injury among helmeted cyclists, though this may have been an artefact of the study design rather than a real effect.
- Inappropriate design does not necessarily under-estimate protective effect of helmets (as claimed by authors). Bias could go in either direction.
- Those wearing non-approved helmets were older.
- Self-report crash circumstances and helmet use.
By Curnow, 2005:
- The conclusions relate to approved helmets in use in 1987-89 which had hard shells (Standards Association of Australia, 1986). Removal of that requirement in 1990 greatly affected the protective value of helmets, but the study makes no mention of it.
- While the study notes some symptoms of brain injury, it avoids discussing its causes. This is despite Dr McDermott, as Chairman of the VRTC, having argued reduced brain damage and life-long disability to convince a federal parliamentary committee to recommend compulsory wearing (AHoR, 1985). When asked then whether brain injury was due to deceleration or rotational forces, Dr McDermott attributed it wholly to the first, 'G forces'. His disregard of angular acceleration contrasts with a statement by his co-author that it plays a major part in brain injury and there is no direct means of damping it (Lane, 1986).
- 22 casualties are excluded from the analysis because their helmets were dislodged in the crash, thereby reducing the number of head injuries among helmeted cyclists. This could be justified only if it were certain that, but for dislodgement, those injuries would not have occurred. The exclusion therefore amounts to assuming that helmets are efficacious - what the study then purports to establish! Data of Tables 3 and 5, Figure 10 and the text show that most of the helmets of the more severely injured (AIS 3 and 4-6) were dislodged. Hence, the study's conclusions that there was a protective effect for head injury of severity AIS 4-6 and that its findings provide evidence of benefit from mandatory wearing are only assumptions.
- The research was carried out under the auspices of the Victorian Road Trauma Committee (VRTC) of the Royal Australasian College of Surgeons (RACS), with financial support from the Government of Victoria. As the VRTC had persuaded that Government to adopt the policy of compulsory wearing in 1984, the efficacy of helmets was clearly not in question for either of them. This suggests that the study was not done to resolve that question, but to support the policy of its sponsors.
By Keatinge and Parry, 1994:
- Study looked only at people who had contacted health services after being injured and included no facts on the relative risk of injury with and without a helmet.
- The authors fail to mention the work of Spaite et al, 1991, who studied cyclists attending a university trauma centre after being hit by cars. Both head and non-head injuries of people who had voluntarily been wearing helmets were less severe than those of people who had not been wearing helmets. Presumably people who voluntarily wore helmets behaved more cautiously in general, perhaps riding more carefully or being more likely to attend hospital after an accident. This sort of confounding means that studies of voluntary helmet wearing cannot test the hypothesis of protection conferred by helmets.
- McDermott and Lane argue that the results of mandatory use of helmets in Victoria, Australia, support the suggestion that helmets have a protective effect against impact from cars. In the first year of compulsory use of helmets, however, cycle use decreased by about 40% while overall deaths of non-cyclists on the roads decreased by 25% (Davis, 1993). Both head and non-head injuries to cyclists decreased. The information from Victoria is not adequate to indicate what, if any, effect compulsory use of helmets is likely to have on injury rates. Human behaviour is too confusing and complex for valid analysis in the face of insufficient numbers, inadequate information, inconstant underlying trends, and a poor scientific approach to data that are selectively quoted and potentially biased from the point of collection (Noseworthy et al, 1994). The published work on Victoria displays all of these problems.
McDermott and Lane challenged Keatinge and Parry with regard to reduced cycle use in Victoria (McDermott and Lane, 1994). They stated:
Keatinge and Parry quote a secondary source to the effect that cycle use in Victoria decreased by 40% after wearing a helmet became compulsory. Cycling by children and teenagers decreased by an average of 36% in the two years after the law was introduced, but cycling overall increased (Cameron, Vulcan, Finch and Newstead, 1994).
But Curnow, 2008 subsequently supported Keatinge and Parry:
In Victoria, surveys measured usage by comparing numbers of cyclists counted and the times taken to ride through marked areas in May 1990, just before compulsory wearing, and again in May of 1991 and 1992. The number and usage of teenagers fell by 46% and 44% respectively by 1991. The number of adults fell by 29%, but change in their usage was not measured because they were not timed in 1990. The Federal Office of Road Safety (FORS) claims an increase for adults by comparing usage after compulsory wearing with that measured in 1987/88, disregarding both a caution by the authors of the surveys that the comparison is unreliable because the earlier survey was done at a different season 3.5 years earlier, and the rising trend in cycling before 1990. The claim is erroneous.
Evidence Given to the Australian House of Representatives Standing Committee on Transport Safety, Motorcycle and Bicycle Helmet Safety Inquiry. 18 Oct 1985, p. 1086.
Cameron, Vulcan, Finch and Newstead, 1994
Cameron MH, Vulcan AP, Finch CF, Newstead SV, 1994. Mandatory bicycle helmet use following a decade of helmet promotion in Victoria, Australia - an evaluation. Accident Analysis & Prevention 1994;26(3):325-337.
Curnow WJ, 2005. The Cochrane Collaboration and bicycle helmets. Accident Analysis & Prevention 2005;37(3):569-573.
Curnow WJ, 2008. Bicycle helmets and public health in Australia. Health Promotion Journal of Australia 2008 Apr;19(1):10-15..
Davis, R, 1993. Death on the streets. Leading Edge Press ISBN 0948135468.
Keatinge and Parry, 1994
Keatinge R, Parry R, 1994. Protection afforded by cycle helmets. BMJ 1994;309:1441 (26 Nov).
Lane JC, 1986. Helmets for child bicyclists, some biomedical considerations. Federal Office of Road Safety, Canberra Report CR47.
McDermott and Lane, 1994
McDermott FT, Lane JC, 1994. Protection afforded by cycle helmets. British Medical Journal BMJ 1994;309:877.
Noseworthy et al, 1994
Noseworthy JH, Ebers GC, Vandervoort MK, Farquhar RE, Yetisir E, Roberts R, 1994. The impact of blinding on the results of a randomized placebo-controlled multiple sclerosis clinical trial. Neurology 1994;44:16-20.
Spaite et al, 1991
Spaite DW, Murphy M, Criss EA, Valenzuela TD, Meislin HW, 1991. A prospective analysis of injury severity among helmeted and non helmeted bicyclists involved in collisions with motor vehicles. Journal of Trauma 1991 Nov;31(11):1510-6..
Thompson, Rivara and Thompson, 1989
Thompson RS, Rivara FP, Thompson DC, 1989. A case control study of the effectiveness of bicycle safety helmets. New England Journal of Medicine 1989 v320 n21 p1361-7.
Towner et al, 2002
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. Department for Transport Road Safety Research Report 30.