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Helmet legislation and admissions to hospital for cycling related head injuries in Canadian provinces and territories: interrupted time series analysis

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f2674 (Published 14 May 2013) Cite this as: BMJ 2013;346:f2674

Re: Helmet legislation and admissions to hospital for cycling related head injuries in Canadian provinces and territories: interrupted time series analysis

The Canadian report mentions that cycle helmet laws are contentious and the focus of active public debate.(1) Fuelling the debate is the uncertainty whether helmets improve safety and helmet requirements discouraging cycling and public health implications . Debate is also about the effectiveness of helmets and their unexpected consequences together with law enforcement and legal consequences.(2)

The article states; “After taking baseline trends into consideration, however, we were unable to detect an independent effect of legislation on the rate of hospital admissions for cycling related head injuries”. It appears that legislation does not provide significant benefit.

The report also states; “Within a province, however, the introduction of helmet legislation does not discourage bicycle use and thus permits assessment of helmet legislation on cycling related head injuries.” Two references No 26 Dennis et al 2010 (3) and No 51 Macpherson et al 2001(4) were provided in support of the statement.

One reply to references 26 states; ‘Reading the article, The effects of provincial bicycle helmet legislation on helmet use and bicycle ridership in Canada (ref 1), it appears the conclusions reached were ill considered and unreliable for a number of reasons’. The reply suggested a reduction in cycling of 47% for Alberta and 8% for Prince Edward Island.(5)

No reply from the authors of Dennis et al was provided.

The other reference was No 51, referring specifically to surveys in East York, a suburb of the city of Toronto.

The conclusion reached was; Contrary to the findings in Australia, the introduction of helmet legislation did not have a significant negative impact on child cycling in this community.
This conclusion has been widely questioned,(6),(7),(8),(9) e.g.

Robinson details that; “The Ontario law was not enforced and the effect on helmet wearing rates was not reported. The results should be interpreted with caution for three reasons.”

The Bicycle Helmet Research Foundation also provides data on Canadian provinces and shows that the helmet laws have discouraged cycling (10).

In the case of British Columbia they provided survey data 4 years apart. The B C surveys were provided in July/August of 1995 and 1999 (7.5% extra cyclists counted in 1999, +269). The survey data indicates that the 16-30 age group had 97 extra wearing helmets compared to 489 fewer cyclists. In the last week of July and first week of August 1995 Vancouver had 88mm of rain compared with 18mm in 1999(11). From 1995 to 1999 the population of B C increased by approximately 200,000 people(12). Greater Vancouver constructed sixteen bikeways from 1986 to 1999, with a total length of 133 km(13). Simply comparing cyclists counted would not give a very accurate evaluation of how helmet law affected cycling levels. Travel Surveys in 1992 and 2001 showed a drop in the bike share of afternoon peak trips from 5.2% to 3.6% in Victoria(14). The fall from 5.2% to 3.6% is effectively a 30% reduction in cycling share.

The article mentions ‘Between 1994 and 2003, the rate of head injuries among young people decreased by 54.0% (95% confidence interval 48.2% to 59.8%) in provinces with helmet legislation compared with 33.1% (23.3% to 42.9%) in provinces and territories without legislation.’ This claim is made without any adjustment for the change in level of cycling activity. It fails to mention that cyclists' length of stay in hospital for head injuries increased by 60% from 4.3 days in 1994/95 to 6.9 days in 2003-04. Across Canada, head injury admissions (all causes) reduced by 53% for those in the 0-19 year age group between 1994/95 and 2003/04, for cyclists aged 0-19 years, it reduced by 55%(15).

When health and safety aspects are considered in detail it appears that the helmets laws in Canada could have done more harm than good. The article fail to fully consider the evidence relating to discouraging cycling and the overall health implications, e.g. In 2001, deaths in Canada due to all circulatory disease were approximately 60,000 compared to 63 from cycling(16).

References
1 BMJ 2013;346:f2674 http://www.bmj.com/content/346/bmj.f2674
2 Clarke, CF, Evaluation of New Zealand’s bicycle law, NZMJ 10 February 2012, Vol 125 No 1349 http://www.cycle-helmets.com/nz-clarke-2012.pdf
3 Dennis J, Potter B, Ramsay T, Zarychanski R. The effects of provincial bicycle helmet legislation on helmet use and bicycle ridership in Canada. Inj Prev2010;16:219-24
4 Macpherson AK, Parkin PC, To TM. Mandatory helmet legislation and children’s exposure to cycling. Inj Prev2001;7:228-30.
5 Clarke CF, Cycle helmet law not properly assessed http://injuryprevention.bmj.com/content/16/4/219.abstract/reply
6 Robinson DL, Helmet laws and cycle use,
http://injuryprevention.bmj.com/content/9/4/380.full
7 Kary M, Potential of a East York dataset, http://injuryprevention.bmj.com/content/18/6/358/reply#injuryprev_el_9824
8 Clarke CF, Worldwide helmet concerns, ,http://injuryprevention.bmj.com/content/12/4/231/reply
9 Clarke CF, Evaluating bicycle helmet use and legislation in Canada, http://www.cycle-helmets.com/canada-helmet-assessment.doc,
10 BHRF, http://www.cyclehelmets.org/1023.html
11 Environment Canada, Climate Services http://www.climate.weatheroffice.ec.gc.ca/climateData/dailydata_e.html?t...
12 Statistics Canada, British Columbia, population
13 The Vancouver Bicycle Network, www.city.vancouver.be.ca/engsves/transort/cycling/general.htm
14 Capital Region District, 1998, 2002a, and 2002b, http://policy.rutgers.edu/faculty/pucher/CanadaCyclingWTPP.pdf
15 Head Injuries in Canada, A Decade of Change, Canadian Institute of Health Information, August 2006
16 Health indicators- January 2005, Statistics Canada – Catalogue no. 82-221, Vol 2005 No1.

Competing interests: No competing interests

20 May 2013
Colin Clarke
Retired
CTC (RTR rep.)
Guildford, GU2