Do crash helmets reduce the severity of head injury in adult pedal cyclists

Date First Published:
April 23, 2001
Last Updated:
August 3, 2011
Report by:
George Graham, Medical Student (Peninsula College of Medicine and Dentistry)
Search checked by:
Saif Al-Nahhas , Peninsula College of Medicine and Dentistry
Three-Part Question:
In [adult pedal cyclists] does [the use of a crash helmet] affect [severity of and outcome following head injury]
Clinical Scenario:
A 32 year old un-helmeted cycle courier is brought to the ED after a collision with a car. He has an isolated severe head injury (GCS=7) and is intubated before transfer to the CT scanner. You wonder if the severity of his injury, or his outcome, would be improved had he been wearing a helmet.
Search Strategy:
Medline 1966- May 2011 using the OVID interface.
Search Details:
(("Bicycling" [Mesh] OR bicycle)) AND (("Head Protective Devices" [Mesh] OR helmet)) AND (("Craniocerebral Trauma" [Mesh] OR head injury))
LIMITS: Human AND English language.
Outcome:
472 papers of which 10 were relevant to the clinical question.
Relevant Paper(s):
Study Title Patient Group Study type (level of evidence) Outcomes Key results Study Weaknesses
Bicycle helmet wearing and the risk of head, face, and neck injury: a French case-control study based on a road trauma reg Amoros E, Chiron M, Martin JL, Laumon B. 2011 France 8373 cyclists with and without helmets with bicycle related trauma Case-control. Trauma registry, 3b Head Injury ISS 1+ Adjusted estimate odds ratio for head injury (ISS 1+) helmet wearers vs non-helmet wearers 0.78 (95% CI 0.67 to 0.90). No separation of adult and child data. Heterogeneity of demographics between cases and controls. Helmet status missing for 39% of cases - results unchanged by this. Trauma Registry data, therefor no record of cyclists uninjured in crashes/not seeking medical aid.
Severe Head Inury ISS 3+ Adjusted estimate odds ratio for severe head injury (ISS 3+) 0.41 (95% CI 0.23 to 0.68).
Helmet use and bicycle-related trauma in patients presenting to an acute hospital in Singapore. Heng KW, Lee AH, Zhu S, Tham KY, Seow E. 2006 Singapore 160 cyclists with and without helmets with bicycle related trauma Cross Sectional. 3b Head Injury Significant (p = 0.01) reduction in incidence of head injury in helmeted group. Odds Ratio for head injury helmet vs non-helmet was 0.14 - not statistically significant. No separation of adult and child data. Proportion of helmeted cyclists 10.6% and small sample size. ISS Significantly higher in unhelmeted casualties. No record of length of hospital stay.
Discharge from Hospital No statistically significant difference in discharge status.
Trends in helmet use and head injuries in San Diego County: the effect of bicycle helmet legislation. Ji M, Gilchick RA, Bender SJ. 2006 USA 1116 cyclists with and without helmets with bicycle related trauma Cross Sectional. Trauma Registry. 3b Serious Head Injury (AIS 3+) Odds ratio for serious head injury, helmet wearers vs non-helmet wearers, 0.43 (0.28-0.66) Trauma registry data. No consideration of minor (ISS <3) head injury.
Bicycle helmet efficacy: a meta-analysis. Attewell RG, Glase K, McFadden M, 2001 Australia 7302 adult cyclists with and without helmets Meta Analysis. 1a Fatal Injury Combined estimate odds ratio, helmet wearers vs non-helmet wearers, 0.27 (0.1-0.71 95%CI) No adjustnment for potential confounders. Unable to consider effect of helmet on rider behaviour
Helmets for preventing head and facial injuries in bicyclists Thompson DC, Rivara F, Thompson R. 1999 USA 4394 cyclists who had crashed while riding a bicycle Meta analysis. 1a Head Injury The summary odds ratio, helmet wearers vs non-helmet wearers, for head injury 0.31 (95% CI 0.26 to 0.37); ; No separation of adult and child data.
Brain Injury The summary odds ratio, helmet wearers vs non-helmet wearers, for brain injury 0.31 (95% CI 0.23 to 0.42)
Severe Brain Injury (AIS 3+) The summary odds ratio, helmet wearers vs non-helmet wearers, for severe brain injury was: adjusted 0.26 (95% CI 0.14 to 0.48)
Effectiveness of bicycle safety helmets in preventing head injuries. A case-control study. Thompson DC, Rivara FP, Thompson RS. 1996 USA 3390 cyclists with and without helmets and bicycle related trauma Case control. Prospective. 3b Head Injury Summary odds ratio, helmet wearers vs non-helmet wearers, for any head injury OR 0.31 (95% CI 0.26-0.37); Heterogeneity of type of helmet used and lack of statistical power to diffentiate between groups. Heterogeneity of cases and controls. Unclear whether helmet wearing is self-report or medical notes.
Brain Injury Summary odds ratio, helmet wearers vs non-helmet wearers, for brain injury OR 0.35 (95% CI 0.25-0.48)
Severe Brain Injury (AIS 3+) Summary odds ratio, helmet wearers vs non-helmet wearers, for severe brain injury OR 0.26 (95% CI, 0.14-0,48).
Injury patterns in cyclists attending an accident and emergency department: a comparison of helmet wearers and non-wearers C Maimaris, C L Summers, C Browning, C R. Palmer. 1994 UK 1040 cyclists with and without helmets and bicycle related trauma Case control. Prospective. 3b Head Injury Adjusted odds ratio for head injury, unhelmeted vs helmeted, 3.25 (95% CI 1.17 - 9.06) No separation of adults and children
The effectiveness of bicyclist helmets: a study of 1710 casualties. McDermott FT, Lane JC, Brazenor GA, Debney EA. 1993 Australia 1710 cyclists with and without helmets and cycling trauma Case control. Prospective. 3b Head Injury Severity Relative proportion for head injury, helmet wearers vs. non-helmet wearers, 0.71 (95% CI 0.58-0.86). Significant increase in the duration of period of loss of consciousness in unhelmeted vs. helmeted cyclists (p=0.05). Significant reduction in head AIS in unhelmeted vs. helmeted No raw data presented for period of LOC or head AIS. Excludes both minor injuries not presenting to ED and cyclists who died at scen or during transport to ED. No separation of child and adult data.
A case-control study of the effectiveness of bicycle safety helmets. Thompson RS, Rivara FP, Thompson DC. 1989 USA 776 cyclists with and without helmets and cyclign related injuries Case control prospective. 3b Head Injury Severity Odds ratio for: head injury, helmet wearers vs. non-helmet wearers, 0.26 (95% CI 0.14-0.42); brain injury, helmet wearers vs. non-helmet wearers, 0.19 (0.06-0.57) Only included patients presenting to ED within one health insurance provider. No separation of adult and child data. Confounding due to variable rates of helmet wearing within different age groups.
Do bicycle safety helmets reduce severity of head injury in real crashes? Dorsch MM, Woodward AJ, Somers RL. 1987 Australia 197 cyclists with and without helmets and a cycling related incident where the head had been struck in past 5 years Cross sectional. Survey. 4 Head Injury Severity, Statistically significant reduction in head injury severity in helmet wearers (Chi squared = 25.0 p < 0.005). Sampling bias: those killed/disabled by injury will not return questionnaire; only surveyed club cyclists. Recall bias. Variable types of helmet used.
Author Commentary:
There is a large body of evidence, including a Cochrane review, that demonstrates bicycle helmets reduce the incidence of head injury.

A reduction in the severity of head injury of helmet wearers has also been demonstrated using head AIS and duration of loss of consciousness, although this is not seen with GCS. The reduction in the odds ratio for head injury with increasing injury severity suggests that helmets may protect against severe injuries to a greater extent than minor injuries.

Evidence for outcomes is conflicting: Attewell demonstrated a reduced odds ratio for fatalities amongst helmeted cyclists, however Heng found no statistical difference in discharge status between helmeted and unhelmeted cyclists.

Bottom Line:
Helmets reduce the incidence of head injuries in cyclists. There is also compelling evidence that also reduce the severity of head injuries. It is reasonable to infer from this that clinical outcome is improved and their use should be encouraged in all cyclists.
References:
  1. Amoros E, Chiron M, Martin JL, Laumon B.. Bicycle helmet wearing and the risk of head, face, and neck injury: a French case-control study based on a road trauma reg
  2. Heng KW, Lee AH, Zhu S, Tham KY, Seow E. . Helmet use and bicycle-related trauma in patients presenting to an acute hospital in Singapore.
  3. Ji M, Gilchick RA, Bender SJ. . Trends in helmet use and head injuries in San Diego County: the effect of bicycle helmet legislation.
  4. Attewell RG, Glase K, McFadden M, . Bicycle helmet efficacy: a meta-analysis.
  5. Thompson DC, Rivara F, Thompson R. . Helmets for preventing head and facial injuries in bicyclists
  6. Thompson DC, Rivara FP, Thompson RS.. Effectiveness of bicycle safety helmets in preventing head injuries. A case-control study.
  7. C Maimaris, C L Summers, C Browning, C R. Palmer. . Injury patterns in cyclists attending an accident and emergency department: a comparison of helmet wearers and non-wearers
  8. McDermott FT, Lane JC, Brazenor GA, Debney EA. . The effectiveness of bicyclist helmets: a study of 1710 casualties.
  9. Thompson RS, Rivara FP, Thompson DC.. A case-control study of the effectiveness of bicycle safety helmets.
  10. Dorsch MM, Woodward AJ, Somers RL. . Do bicycle safety helmets reduce severity of head injury in real crashes?