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Bicycle helmet prevalence two years after the introduction of mandatory use legislation for under 18 year olds in Alberta, Canada

Hagel BE, Rizkallah JW, Lamy A, Belton KL, Jhangri GS, Cherry N, Rowe BH.
Injury Prevention, 2006;12:262-265.

Original paper

 

Summary of paper (Authors' abstract)

Objective: To determine changes in helmet use in cyclists following the introduction of a bicycle helmet law for children under age 18.
Methods: Cyclists were observed by two independent observers from July to August 2004 (post-legislation) in Edmonton, Alberta. The data were compared with a similar survey completed at the same locations and days in July to August 2000 (pre-legislation). Data were collected for 271 cyclists in 2004 and 699 cyclists in 2000.
Results: The overall prevalence of helmet use increased from 43% (95% CI 39 to 47%) in 2000 to 53% (95% CI 47 to 59%) in 2004. Helmet use increased in those under 18, but did not change in those 18 and older. In the cluster adjusted multivariate Poisson regression model, the prevalence of helmet use significantly increased for those under age 18 (adjusted prevalence ratio (APR) 3.69, 95% CI 2.65 to 5.14), but not for those 18 years and older (APR 1.17, CI 0.95 to 1.43).
Conclusion: Extension of legislation to all age groups should be considered.

BHRF Commentary

Evidence of reduced children's cycling ignored

Although the authors state they did not capture information on all cyclists (only those passing by the research team), the number of child cyclists fell between 2000 and 2004 from 10.3% to 4.8% of all cyclists and teenagers from 15.4% to 10.3%, a very significant reduction (p=0.0015). Given the average of 0.6 child and 1.3 teenage cyclists recorded per site (compared to 10.5 adults), it seems likely that, if any more child cyclists had been present, a team of three people (one controller and two observers) should have been able to count them.

The researchers took great pains to present some extremely complicated statistics to show that helmet wearing increased from 44% to 100% of children, 17% to 75% of teenagers, but remained at 48-49% of adults. It is unfortunate that they did not attempt to estimate whether the increased helmet wearing was achieved at the expense of discouraging cycling. Given the considerable health benefits of cycling (BHRF, 1015), and previous studies showing that helmet laws reduce cycle use (BHRF, 1020), this should have been a primary focus of the study.

Subsequent data has shown that children's cycling in Alberta fell by 56 to 59 percent and teenagers' cycling by around 27% (BHRF, 1250; Karkhaneh, 2011).

Age Group
Cyclists counted
% all cyclists

2000
2004
Reduction
2000
2004
<13
66
13
80.3%
10.3%
4.8%
13 - 17
98
28
71.4%
15.4%
10.3%
18+
474
230
51.5%
74.3%
84.9%
Total
638
271
57.5%
100%
100%

No evidence of injury reduction

The authors state that because the helmet law increased the proportion of cyclists wearing helmets, legislation should be considered for all age groups. However, head injury rates are not mentioned. Another source has claimed that across 9 health regions in Alberta head injuries doubled from 5% to more than 10% of cyclist injuries in the 6 months following introduction of the law, though this may have been due partly to changes in the way data were coded (BHRF, 1055).

Several other studies (e.g. Robinson, 2006; Ming, Gilchick and Bender, 2006) have shown that, despite large increases in helmet wearing, enforced laws have had little effect on head injury rates, but have detrimentally affected public health by substantially reducing the amount of cycling. It is therefore strange that the authors recommend new helmet laws, without any evidence that existing legislation has been effective in decreasing head injuries.

Subsequent data has shown that injuries to children in Alberta after the law were more than twice as many as would be expected following the reduction in cycle use (BHRF, 1250; Karkhaneh, 2011).

Wrong basis for adult law proposal

To support their recommendation that the present Alberta helmet law should be extended to all age groups, the authors refer to data from Toronto of child cyclists under 15 years of age (Khambalia, Macarthur and Parkin, 2005) and state that children riding with helmeted adults are almost 10 times more likely wear a helmet than children riding with non-helmeted children. A more appropriate comparison, though, is between children riding with helmeted and non-helmeted adults. In Toronto, children were just under 2.5 times more likely to wear a helmet when riding with helmeted adults.

However, later and more relevant data are available from Alberta itself (Alberta CICR, 2001). These show that 99% of children wear helmets if their adult companion is helmeted and 84% if not. Thus children are only 1.18 times more likely to wear a helmet riding with a helmeted adult. This is very much less than the 10 times suggested by the authors using less relevant data.

Bias in selection of evidence on helmet benefits

Two references are cited in support of helmet effectiveness but the second (Thompson, Rivara and Thompson, 2002-9) examined an exclusive subset of the same papers considered by the first (Attewell, Glase and McFadden, 2001). Moreover, the second authors' own work dominated both analyses. There is no acknowledgement that these analyses have been widely criticised for bias, nor is there any reference to any paper sceptical of helmet effectiveness.

The suggestion that helmets reduce fatal injuries by 73% is particularly unsound. The cited reference simply presents an odds ratio of 0.27 without any attempt to adjust for confounders. More robust data based on whole populations and research specifically targeted at cyclist fatalities has failed to show any significant benefit from cycle helmets in preventing deaths (BHRF, 1012). In any case, NEISS data suggests that fewer than half (45%) of bicyclist deaths are due to head injury (BHRF, 1177), so how could helmets possibly reduce fatalities by as much as 73%?

Conclusion

The data presented in this paper strongly suggest that Albert's child helmet law has led to a large decrease in cycling by children and teenagers, but this outcome is not even mentioned by the authors. Similarly the authors provide no evidence as to whether the law has been successful in reducing the risk of head injury.

The methodology used for the study is weak and its scope too selective. In the absence of strong evidence that the present law has been beneficial in reducing head injuries to cyclists (this paper provides no evidence of any benefit), the authors' conclusion is not justified. If the only outcome of the law has been to reduce cycling, it would be logical and in the interests of public health to recommend that the law should be repealed.

References

Alberta CICR, 2001

Bicycle Helmets Observational Study Summary. Alberta Centre for Injury Control and Research, c.2001 .2001.

Attewell, Glase and McFadden, 2001

Attewell RG, Glase K, McFadden M, 2001. Bicycle helmet efficacy: a meta-analysis. Accident Analysis & Prevention 2001-05 v33 n3 p345-52.

BHRF, 1012

What evidence is there that cycle helmets save lives?. .

BHRF, 1015

The health benefits of cycling. .

BHRF, 1020

How helmet promotion and laws affect cycle use. .

BHRF, 1055

Head injuries up after Alberta law?. .

BHRF, 1177

NEISS data on bicyclist injuries. .

BHRF, 1250

Alberta's helmet law children's cycling halved, injuries increased per cyclist. .

Karkhaneh, 2011

Karkhaneh M, 2011. Bicycle helmet use and bicyclists head injuries before and after helmet legislation in Alberta Canada. University of Alberta .

Khambalia, Macarthur and Parkin, 2005

Khambalia A, Macarthur C, Parkin PC, 2005. Peer and adult companion helmet use is associated with bicycle helmet use by children. Pediatrics 2005;116(4):939-942.

Ming, Gilchick and Bender, 2006

Ming J, Gilchick RA, Bender SJ, 2006. Trends in helmet use and head injuries in San Diego County: The effect of bicycle helmet legislation. Accident Analysis & Prevention 2006;38(1):128-134.

Robinson, 2006

Robinson DL, 2006. Do enforced bicycle helmet laws improve public health?. BMJ 2006;332:722-725.

Thompson, Rivara and Thompson, 2002-9

Thompson DC, Rivara FP, Thompson RS., 2002. Helmets for preventing head and facial injuries in bicyclists (Cochrane Review). Cochrane Database Syst Rev issue 4, 2002.

See also