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Critique of BMA paper
Hot off the modem:
http://www.cyclehelmets.org/mf.html#1101 Legislation for the compulsory wearing of cycle helmets ================================================== ===== Board of Science and Education, British Medical Association, November 2004 Summary ======= In response to correspondence from a number of its members, the BMA has reconsidered its policy on this issue. Previous policy attached significant emphasis on the BMA's wish not to discourage cycling by making helmets compulsory. BMA cites evidence that it believes shows that helmet legislation no longer leads to less cycling, and that helmets have proven effective in protecting against head, brain, severe brain and facial injuries, as well as death, as a result of cycling accidents. It therefore believes that the BMA should support the introduction of legislation making the wearing of helmets compulsory for both children and adults. It is important that legislation should be enforced and complemented by educational and promotional campaigns. Other measures, such as cycle training and the creation of a safer cycling environment, should also be pursued. Comment ======= The BMA paper is not a comprehensive or balanced review of evidence. Its references have been accepted at face value even when the subject of published criticism or contradictory evidence. Some of the facts on which the paper relies are simply wrong. Legislation as a deterrent to cycle use --------------------------------------- The BMA states that evidence from Australia that helmet laws discourage cycling is outdated, "and contains distortions from variables including a reduction in the legal age of driving that meant more teenagers travelled in motor vehicles". The driving age was lowered, from 18 to 17, only in the state of Victoria, where pre-law 17-year olds accounted for 6% of cycle traffic [1]. Even if every 17-year old cyclist had changed completely to driving, that would account for only a small part of the 43% drop in cycling by Victorian teenagers post-law. It would not account at all for the decline of up to 60% in cycling among teenagers elsewhere in Australia. Evidence from Australia indicates that its helmet laws continue to deter cycle use and that in most parts of the country cycling levels are still well below pre-law levels. Where cycling levels have recovered, there has been the loss of more than a decade of cycling growth (cycling levels were generally increasing pre-law), and in some places part of the new increase is due to population growth. Furthermore there have been shifts from regular utility cycling (which yields the greatest health benefits) to leisure cycling, and in the average age of cyclists, with considerably fewer children now riding [2]. In the Australian state of Northern Territory, the mandatory helmet law has been partially repealed, leading to wearing rates of only 15 - 20% today. Yet this state now has the highest proportion of people who cycle in Australia and the lowest ratio of cyclist hospital admissions to population. [3] In other countries, too, there is clear evidence that helmet laws have a large and long-lasting effect on cycle use. In New Zealand, cycling by schoolchildren remains 40% lower than before the helmet law [4]. In Nova Scotia, Canada, cycle use fell by 40% to 60% following the introduction of a helmet law, with the largest decrease among teenagers [5]. The BMA bases its claim that helmet legislation does not reduce the numbers of children cycling on a single report [6] based solely on Ontario, Canada. However, as that report acknowledges, the helmet law in Ontario was not enforced, which could explain why the number of child cyclists did not reduce [7]. Yet the BMA is seeking strong enforcement of new helmet laws. The Ontario report has also been criticised for its limitations; for example it was based on a small sample size and did not consider cycle use by older children who are the most likely to give up cycling [8]. Helmet use ---------- The BMA says that cycle helmet use is rising, from 16% in 1994 to 25% in 2002, suggesting that it would now be more acceptable to introduce a helmet law. However, these rates only reflect use by adults on main roads. Helmet use by children declined over the same period from 17.5% to 15.2% (16.0% to 12.3% for boys who are 5 times more at risk than girls), indicating that children still have no desire to wear helmets. On minor roads, where most cycling takes place, wearing rates were 10.9% for adults, 6.5% for children in 2002 [9]. The scale of the 'problem' -------------------------- According to the BMA, each year over 50 people aged 15 years and under are killed by cycling accidents, of whom 70 to 80 per cent die from traumatic brain injury. These statistics are grossly in error. In 2002, 19 children were killed in cycling accidents in England, of whom 10 died as a result of head injuries [10]. In Scotland the same year, no child cyclist died of head injury [11]. Hospital data for England shows that in 2002-3 there were just over 2,000 admissions for head injury to children when cycling. Of these, no more than a few hundred (max 516) were serious injuries with the potential for mitigation by cycle helmets. This is in the context of 6 million children who cycle in England. [12] The BMA repeats speculation that there are 90,000 cycling accidents each year on-road, and 100,000 off-road. There is no scientific basis to assert such figures and they are not relevant to the paper. The vast majority of injuries to cyclists do not involve head injury and usually amount to no more than cuts or bruises. The evidence ------------ The BMA says that studies in a number of countries have shown that high usage rates of helmets as a result of legislation is associated with a reduction in cycle related deaths and head injuries. However, large-population studies have not shown a beneficial link between helmet use and fatalities. The largest ever survey, of over 8 million cases of injury and death to cyclists in the USA over 15 years, concluded that there was no evidence that helmets had reduced head injury or fatality rates [13]; indeed, it suggested that helmeted riders were more likely to be killed. Other studies from the USA [14] and Canada [15] based on whole populations have also found no effect on fatalities. In New South Wales (Australia) in the 3 years following the enactment of its helmet law, 80% of cyclists killed and 80% of those seriously injured had worn helmets. These proportions were almost identical to helmet wearing rates at the time [16] [17] [18]. More recent reports from Australia suggest that increases in helmet wearing have had little, if any, positive impact on head injuries [19] [20]. A similar situation has been reported in New Zealand [21]. Outside the context of helmet laws, increasing helmet use does not appear to have influenced fatal or serious injury trends in Great Britain [22] or Germany [23]. In the USA, helmet use increased from 18% to 50% of cyclists from 1991 to 2001 whilst the absolute number of head injuries went up 10%. Pro-rata cycle use, cyclists in 2001 were more likely to suffer a head injury than a decade earlier [24]. One paper cited by the BMA [25] has been criticised for presenting insufficient information by which to assess the validity of its methodology [26]. It was funded by the Snell Foundation, whose income is derived in part from helmet sales, and the benefits predicted are not supported by any large population evidence. The Cochrane Review [27] was written by the same authors and has been criticised for its lack of impartiality. 4 of the 7 papers reviewed - representing more than three-quarters of the cyclists studied - are by the authors themselves and dominate the analysis. The papers suggesting the greatest protective effects for helmets have been widely criticised for comparing quite different groups of cyclists. Much of this criticism has been appended to the Review in the form of criticism and contrary evidence, but this seems not to have been taken into account by the BMA. The BMA cites a New Zealand study that demonstrated a 19 per cent reduction in head injuries to cyclists following legislation. However, further analysis of the original data for this report showed that the reduction in head injuries after the law was the returning to normal of cyclist injury trends that had risen immediately before the law, during rising helmet use. Taken across the full pre/post law period, there was no improvement in head injuries to cyclists greater than that enjoyed by the population as a whole [28] [21]. The New Zealand Household Travel Survey shows that cycling hours decreased by 34% from 1989 to 1997, or approximately 22% following the helmet law. This cancels out the 19% reduction in head injuries suggested by Scuffham et al [29]. Reference to a decrease in head injuries in Victoria, Australia is misleading, as is the source cited. A problem is that other legislation relating to speeding and drink-driving was introduced around the same time as the state's helmet law. A consequence of this is that pedestrian fatalities fell by 45% in the year following the laws, although this clearly had nothing to do with the helmet law. Cyclists, too, would have benefited from the other laws, so it is not possible to determine any benefit from the helmet law in isolation. However, the helmet law did result in a fall of 44% in cycling by teenagers and a fall of 29% in cycling by adults, which in itself would account for most of the 40% fall in cyclist head injuries. Some researchers have concluded that cyclists were more likely to suffer head injuries as a result of the helmet law [30]. Enforcement ----------- The BMA refers to an education programme in Reading [31] that resulted in an increase in helmet use and a concurrent decrease in cycling-related injuries. This paper has been criticised for its poor methodology. Helmet use was judged by self-reporting alone, with no independent verification. The intervention town and the control town (Basingstoke) were quite different in character and the nature of cycling in the two towns would have been different. There was no monitoring of cycle use against which to compare decreases in injuries. The conclusion of the Reading report, that an increase from 11% to 31% in the proportion of children wearing helmets led to a 45% reduction in head injuries, is implausible even if helmets were 100% effective. Correlation of this report with an earlier report [32], suggests that at least part of the decrease in head injuries occurred before the increase in helmet wearing. Road casualty data for the Reading area shows no benefit for child cycling casualties; indeed, there is a peak in the (very small) number of serious injuries towards the end of the research period. References ---------- [1] Day to day travel in Australia 1985-6. Federal Department of Road Safety, 1989. [2] The West Australia. 10th March 2004. [3] Australia Cycling: Bicycle ownership, use and demographics. Draft report, 2004. [4] New Zealand Travel Survey 2004, Land Transport Safety Authority. [5] Hats off (or not?) to helmet legislation, Chipman R. Canadian Medical Association Journal 2002, 166(5). [6] Mandatory helmet legislation and children's exposure to cycling, Macpherson AK et al. Inj Prev 2001;7(3):228-230 [7] Butting heads over bicycle helmets, Avery AJ, CMAJ, www.cmaj.ca/cgi/eletters/167/4/338 [8] Helmet laws and cycle use, Robinson DL. Injury Prevention 2003;9:380–383. [9] Cycle helmet wearing in 2002, Gregory K, Inwood C, Sexton B. Transport Research Laboratory Report 578, 2003. [10] Parliamentary Question by Brian Jenkins MP, answered by Dr Ladyman, Department of Health. Hansard Written Answers, 10th November 2003. [11] Data from General Register Office, Scotland. [12] Analysis of hospital admissions data for England 1995/6 - 2002/3. Awaiting publication. [13] Reducing Bicycle Accidents: A re-evaluation of the impacts of the CPSC bicycle standard and helmet use, Rodgers. Journal of Product Liability, Vol 11 pp 307-317, 1988. [14] Latest CPSC helmet standard and US fatality trends, Kunich, 2002. [15] Cyclist fatalities in Canada 1975 to 2002, Burdett, 2003. [16] Head injuries and bicycle helmet laws. Robinson DL. Accident Analysis and Prevention, 1996 Jul;28(4):463-7. [17] Road Traffic Accidents in New South Wales, 1992, 1993, 1994. Roads and Traffic Authority of New South Wales. [18] An observational study of law compliance and helmet wearing by bicyclists in New South Wales 1993. Smith NC, Milthorpe FW. Roads and Traffic Authority NSW, 1993. [19] Head injuries and bicycle helmet laws, Robinson DL, Accident Analysis & Prevention, 1996 Jul;28(4):463-75 [20] An Economic Evaluation of the Mandatory Bicycle Helmet Legislation in Western Australia. Hendrie D, Legge M, Rosman D, Kirov C. 1999. Road Accident Prevention Research Unit, University of Western Australia [21] Changes in head injury with the New Zealand bicycle helmet law. Robinson DL. 2001. Accident Analysis & Prevention: 2001 Sep;33(5):687-91 [22] Trends in cyclist casualties in Britain with increasing cycle helmet use. Franklin JA, 2000. [23] Specific patterns of bicycle accident injuries - An analysis of correlation between level of head trauma and trauma mechanism. Möllman FT, Rieger B, Wassmann H. DGNC Köln, 2004. [24] Data from Consumer Product Safety Commission. Report in New York Times, 29th July 2001. [25] Circumstances and severity of bicycle injuries, Thompson DC, Rivara FP, Thompson RS. 1996. Snell Memorial Foundation. [26] Bicycle helmets - a review of their effectiveness. Department for Transport Road Safety Research Report No 30, 2002. [27] Helmets for preventing head and facial injuries in bicyclists, Thompson et al. Cochrane Database Syst Rev. 2000;2:CD001855 [28] The bicycle helmet legislation, curse or cure?, Perry N. University of Canterbury, 2001. [29] Land Transport Safety Authority. ww.ltsa.govt.nz/research/travel_survey/research/travel_survey.html [30] Helmet laws, numbers of cyclists and accident rates, Robinson DL. [31] A hospital led promotion campaign aimed to increase bicycle helmet wearing among children aged 11-15 living in West Berkshire 1992-1998, Lee et al. Injury Prevention 2000, 6:151-153. [32] A bicycle helmet promotion campaign for the under 16 year olds in West Berkshire, England 1992-1995, Lee & Smyth. Pro Velo Australis International Bicycle Conference, Freemantle, Western Australia, 1996. Guy -- May contain traces of irony. Contents liable to settle after posting. http://www.chapmancentral.co.uk 88% of helmet statistics are made up, 65% of them at Washington University |
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Just zis Guy, you know? wrote: Hot off the modem: http://www.cyclehelmets.org/mf.html#1101 Legislation for the compulsory wearing of cycle helmets ================================================== ===== Excellent critique - just needs a few references filling in e.g. 14, 15 have no reference to where they were published. Otherwise can we get the CTC to send a personal copy to every member of the Science & Education Board. Helen, can you, as a member get hold of a list of the Board members? Tony |
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On 11 Nov 2004 10:19:11 -0800, "Tony Raven"
wrote in message .com: Excellent critique - just needs a few references filling in e.g. 14, 15 have no reference to where they were published. Still a bit of a work in progress, but the cabal (TINC) are honing it as we speak. Otherwise can we get the CTC to send a personal copy to every member of the Science & Education Board. Helen, can you, as a member get hold of a list of the Board members? Without wishing to make any suggestion which could be construed as implying anything regarding membership of the cabal (TINC), or indeed the secret society which is behind the site, I think it is safe to say we have that angle covered :-) This could be read as implying that I am in some way connected with cyclehelmets.org. This would be entirely correct. Guy -- May contain traces of irony. Contents liable to settle after posting. http://www.chapmancentral.co.uk 88% of helmet statistics are made up, 65% of them at Washington University |
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