Bicycle Injury Interventions

Bicycle Helmet Effectiveness

Background

Although it makes inherent sense that helmets would be protective against head injury, establishing the real-world effectiveness of helmets is important. The magnitude of the protective effect is important for prevention programs. Laboratory data (ANSI or Snell) are not enough; real-world data are necessary to determine whether helmet use is effective in preventing head injuries. Randomized controlled trials (RCT) are neither feasible nor ethical toward this end. Cohort studies are also unfeasible because of the large population required for follow-up. Case-control studies are a good and efficient design, but should control for confounders such as age, sex, education, income, and crash severity. A number of case-control studies have been conducted demonstrating the effectiveness of bicycle helmets.


Review of bicycle helmet effectiveness studies:

Author

Attewell, 2001

Study design and target population

Meta-analysis of 16 articles.

Included studies with individual injury and helmet use data published 1987-1998.

Included all studies published in English in peer reviewed journals.

Intervention

Bicycle helmet use

Outcomes

Head injury, brain injury, facial injury as defined by the various studies as well as fatal injuries.

13 articles determined injury from medical record; 3 from self-report of injury.

Results

Strong protective effect among helmet users versus non-users for head, brain, facial, and fatal injuries.

Head injury, OR=0.40 (0.29, 0.55), Brain injury, 0.42 (0.26, 0.67), Facial injury, 0.53 (0.39, 0.73), Fatal injury, 0.27 (0.10, 0.71)

Study quality and conclusions

Selection critieria and statistical techniques clearly explained.

Results provide clear evidence of helmet benefits.

Helmets reduce risk of head, brain, facial injury, and death.

Helmet use should be encouraged for all riders.



Author

Kelsch, 1996

Study design and target population

Prospective study 76 hospitalized cyclist, 1994. Goppingen, Germany

Intervention

Bicycle helmet use

Outcomes

Head and brain injury, and death.

(2 deaths in unhelmeted cyclists, no deaths in helmeted group).

Results

Crude OR=0.57 for risk of head injury comparing helmeted to unhelmeted cyclists.

73% of unhelmeted head injured had skull fractures or intracranial injuries; no serious HI in helmeted group.

Study quality and conclusions

Small series hospitalized cyclists.

Bicycle helmets reduced the incidence and severity of head injuries.



Author

Finvers, 1996

Study design and target population

Prospective cohort with nested case control study.

Children ages 3-16 years treated at tertiary care childrens' hospital emergency room, Calgary, Alberta, Canada 1991-93.

Intervention

Bicycle helmet use

Outcomes

Head injuries among helmet users and non-users.

Cases: Serious HI defined as concussion, fracture, crush injuries.

Controls: Mild HI included bruises, lacerations, and abrasions.

Major and minor injuries classified by authors, no ICD 9 codes used.

Results

Helmet use significantly reduced risk of serious head injury by 68% comapred to non-users (OR=0.32 95% CI .11-.89)

No significant difference in serious injuries of all types comparing helmeted and non-helmeted users. (OR=0.9 95% CI 0.6-1.4)

Indicates crash severity similar for both groups.

Multivariate analysis not used.

Study quality and conclusions

Strong prospective effect of helmets for serious head injuries.

Protective effect of helmet underestimated due to exclusion of ICU cases. None of the ICU cases wore helmets.

Tertiary care study, not population based.



Author

Acton, 1996

Study design and target population

Case series;

Part of Brisbane bicycle study. Children <15 years. n=813, 321 with facial injuries.

Intervention

Bicycle helmet use

Outcomes

Oral maxillofacial injuries.

Results

321 children had 340 injuries.

Facial abrasions, lacerations, 171 (50.3%). Soft tissue injuries to mouth, 105 (30.9%). Dentoalveolar trauma, 33 (9.7%). Fractures, 31 (9.1%). 52% wore helmets.

Current helmets offer no protection to face.

Did not divide face into regions. Upper and lower portions of face should have been analyzed separately.

Study quality and conclusions

Oral maxillofacial injuries frequent.

Design modification helmets need such as a lightweight chin protector.



Author

Thompson et al., 1996

Study design and target population

Case-control study

Bicyclist incidents resulting in emergency room visits to one of seven Seattle-area hospitals from March 1992 through August 1994. (n=3390)

Cases: those treated for head injury, hospitalized, or died at scene

Controls: injured cyclists with injuries other than to head

Intervention

Use of three types of bicycle helmets, classified as hard-shell, thin-shell, or no-shell

Outcomes

Head injuries among helmet users and non-users. Head injury classified as any head injury, brain injury, and severe brain injury (classifications using ICD-9 codes and AIS scores).

Results

Protective effect among helmet users versus non-users for any head injury (OR=0.31, 0.26-0.37), brain injury (OR=0.35, 0.25-0.48), and severe brain injury (OR=0.26, 0.14-0.48). Odds ratios adjusted for age and motor vehicle involvement.

Equal effectiveness of helmet in crashes with motor vehicles (OR=0.31, 0.20-0.48) and without motor vehicles (OR=0.32, 0.20-0.39). Similar effectiveness for all age groups.

No differences seen in protective effect among helmet types.

Study quality and conclusions

Bicycle helmets are effective for all bicyclists regardless of age and regardless of motor vehicle involvement in the crash.

Largest prospective case-control study of helmet effectiveness to date. 88% response rate.



Author

Thompson et al., 1996

Study design and target population

Case-control study

Bicyclist incidents resulting in emergency room visit to one of seven Seattle-area hospitals between March 1, 1992 and August 31, 1994. (n=3388)

Cases: those treated for serious facial injuries

Controls:

Set 1: those treated for non-facial and non-head injuries only

Set 2: those treat for non-facial injuries only (i.e., head injuries retained in this control group)

Intervention

Bicycle helmet use

Outcomes

Facial injuries among helmet users and non-users.

Facial injury defined as any injury of the jaw, lips, cheeks, nose, ears (external), eyes (external), forehead, or mouth (intraoral). Cases restricted to fractures or lacerations of these areas.

Head injuries defined as superficial lacerations, abrasions, or contusions on the scalp, as well as skull fractures, concussions, cerebral contusions, serious lacerations, and all intracranial hemorrhages (excluding injuries to the forehead and ears).

Facial injuries stratified by region: upper, middle, and lower face.

Results

Helmet use significantly reduced risk of injury to upper and middle face regions by approximately 65% compared to non-users (Upper face: OR=0.36, 0.26-0.49; Middle face: OR=0.35, 0.24-0.50).

Helmet use had no significant effect on reducing the risk of injury to the lower face compared to non-users (OR=0.88, 0.72-1.07).

Odds ratios adjusted for age, speed, and surface of crash site.

Study quality and conclusions

Helmets protect against upper face and middle face injuries.

Use of two control groups thought to "bracket" the true effect of helmets on risk of facial injury.

General bicycle helmets with chin protection should be developed.



Author

Maimaris et al., 1994

Study design and target population

Case-control study

Bicyclist incidents resulting in emergency room visits to Addenbrooke’s Hospital, Cambridge, 1992. (n=1040)

Cases: those treated for head injury

Controls: those treated for other injuries

Intervention

Bicycle helmet use

Outcomes

Head injuries among helmet users and non-users.

Head injury present if evidence of skull fracture, brain injury shown by CT, or loss of consciousness or post-traumatic amnesia was associated with important post-concussion symptoms.

Crash types stratified into motor vehicle, other bicycle, pedestrian, and fall categories.

Results

No significant differences in type of crash between helmet users and non-users.

Significant protective effect among helmet users for head injury (OR=0.30, 0.11-0.85) compared to non-users.

Significantly higher proportion of children (16%) than adults (9%) used helmets (p<0.001).

Study quality and conclusions

Good case ascertainment.

Helmet use significantly reduces the risk of sustaining a head injury, regardless of type of bicycle accident.

Some evidence refuting claims that helmet users are either more cautious or take more risks than non-users (8.1% head injury among non-helmeted bicyclists; 9.2% among non-owners; 3.5% among helmet users).



Author

Thomas et al., 1994

Study design and target population

Case-control study

Bicycle incidents among children <15 yrs seen in two Brisbane, Australia, hospitals between April 15, 1991, and June 30, 1992.

(n=445)

Cases: those treated for head injury

Controls:

Set 1: those treated for other injuries

Set 2: those treated for facial injuries only

Intervention

Bicycle helmet use

Outcomes

Head and facial injuries among helmet users and non-users.

Head injury (injury to skull, forehead, scalp, or loss of consciousness) assessed by clinician using standard Queensland injury surveillance prevention project form. Facial injuries not defined.

Crash data collected via self-administered questionnaire completed by child and child’s carer.

Risk estimates adjusted for sex, age, hospital, parental education, main cause of accident, contact with moving vehicle or stationary object, and severity of impact.

Results

Children with head injury were more likely to have made contact with a moving vehicle than control children (19% v. 4%, p<0.001).

Helmet use significantly reduced the risk of head injury by 63% (OR=0.37, 0.20-0.66).

Helmet use signficantly reduced the loss of consciousness by 86% (OR=0.14, 0.05-0.38).

No significant reduction in crude risk of facial injuries between helmet users and non-users. (OR=1.15, 0.64-2.04).

Study quality and conclusions

Helmet use significantly reduces the risk of upper head injury and loss of consciousness in a bicycle crash.

Helmet use does not signifiacntly reduce the crude risk of facial injury (no adjusted OR could be calculated from data given).



Author

McDermott et al., 1993

Study design and target population

Population-based case-control study

Bicycling incidents seen in two Melbourne, Australia, hospitals, April-Dec, 1987 and Sept-May, 1989. (n=1710)

Cases: those treated for head injury

Controls: those treated for other injuries

Intervention

Bicycle helmet use

Outcomes

Fatalities, head and facial injuries

Results

Helmet use significantly protects against head injury (crude OR=0.61, 0.47-0.80) and facial injury (crude OR=0.64, 0.49-0.84).

No significant differences in mortality rates between helmeted (approved or non-approved) and non-helmeted bicyclists.

Study quality and conclusions

No adjustments made for age, sex, education, income, or crash severity.

Excluded cyclists who died at scene of crash or who were DOA (n=7).



Author

Spaite et al., 1991

Study design and target population

Case-control study

All bicyclists involved in collisions with motor vehicles reporting to University Medical Center, Tucson, AZ, 1986 through 1988 where helmet status was known. (n=284)

Cases: those treated for head injury

Controls: those treated for other injuries

Intervention

Bicycle helmet use

Outcomes

Fatalities, head and other injuries, Injury Severity Scores (ISS).

Major head injury defined as ISS>15.

Results

Children over six times less likely to wear helmet (OR=0.15, 0.06-0.34) and over twice as likely to sustain a severe head injury (ISS>15) than adults (OR=2.61, 1.26-5.42).

Helmeted riders over 33 times less likely to sustain a major head injury (OR=0.03, 0.01-0.19) and over 16 times less likely to have an ISS>15 than non-helmeted riders (OR=0.06, 0.02-0.15).

Study quality and conclusions

No adjustments made for age or gender.

Case selection most likely biased in that patients with minor injuries or those patients not seen in ER missed.



Author

Thompson et al., 1990

Study design and target population

Case-control study

Bicycle-related injuries

resulting in ER visit to one of five Seattle-area hospitals, Dec 1986 through Nov 1987. (n=531)

Cases: those treated for facial injuries, with no concurrent head injuries

Controls: those treated for injuries to other body areas.

Intervention

Bicycle helmet use

Outcomes

Type and location of facial injuries (upper, lower, or entire face) among helmet users and non-users.

Serious facial injury defined as lacerations, fractures of the facial bones, and fractures of the teeth.

Results

Significant protective effect among helmet users for serious upper facial injuries (OR=0.27, 0.10-0.80) compared to non-users.

No definite association between helmet use and all facial injuries (OR=0.69, 0.41-1.1) or serious facial injuries (OR=0.81, 0.45-1.5).

Study quality and conclusions

Good case ascertainment.

Current helmet designs have little or no protective effect on overall risk of facial injury, but do protect against serious upper facial injury.

Sample size was relatively small and 95% confidence intervals were wide.



Author

Thompson et al., 1989

Study design and target population

Population-based case-control study

Bicyclist head injuries resulting in ER visit to one of five Seattle-area hospitals, Dec 1986 through Nov 1987. (n=668)

Cases: those treated for head injuries

Controls:

Set 1: other ER patients treated for non-head bicycle injuries

Set 2: population-based controls from local health maintenance organization

Intervention

Bicycle helmet use

Outcomes

Head and brain injuries

Results

ER-based controls:

Protective effect against head injury (OR=0.26, 0.14-0.49) and brain injury (OR=0.19, 0.06-0.57).

Population-based controls:

Protective effect against head injury (OR=0.15, 0.07-0.29) and brain injury (OR=0.12, 0.04-0.40).

Study quality and conclusions

Helmet use protects against risk of head and brain injury by 85% and 88% respectively compared to those not wearing helmets.

Population-based control group provides the best estimate of helmet effect.

Odds ratio summary tables

Head injury (image)

Facial injury (image)

Brain injury (image)

Summary of bicycle helmet studies

In all studies reviewed, there are consistent data indicating that wearing an industry-approved bicycle helmet significantly reduces the risk of head injury during a crash or collision. The reduction in risk is somewhat dependent on whether the controls originate from the emergency department or the population at large. However, population-based controls provide the best estimate of helmet effectiveness and allow it greatest generalizability. Overall, helmets decrease the risk of head and brain injury by 70 to 88 percent and facial injury to the upper and mid face by 65 percent.

Cochrane Review: Helmets for preventing head and facial injuries in bicyclists

This evidence-based review contains a comments and criticisms section with our responses to 4 critics of bicycle helmet effectiveness: Bill Curnow, Dorothy Robinson, Richard Keatinge and Mayer Hillman. These criticisms and our replies are published on the Cochrane Injuries group web site http://www.cochrane-injuries.lshtm.ac.uk/helmetcomment.pdf.

This website, Bicycle Helmet Safety Institute, contains a broad range of bicycle helmet and safety information. Additionally, a comprehensive review of bike helmet effectivenss by Dr. Michael Henderson of NSW, Australia, can be accessed at http://www.helmets.org/henderso.htm.

 

Recommendations on bicycle helmet programs

The ongoing advances in bicycle helmet design may enable manufacturers and promoters of helmet use to circumvent obstacles against helmet use such as poor fit and poor air circulation, high cost, and the 'uncoolness' of wearing a helmet. These obstacles -especially peer pressure-are particularly difficult to overcome among children. The data here show that persons wearing helmets are most likely to ride with other wearers their own age (helmeted adults tend to ride with helmeted adults; helmeted childre n tend to ride with helmeted children). While it remains to be seen whether this trend will be come more prevalent as younger birth cohorts have children of their own. It should be made clear that arguments against using bicycle helmets are not evidence- based; bicycle helmets are the most effective means of preventing head and brain injury and should be a requirement for cyclists of all ages.

From the conclusive evidence compiled here, it is recommended that effective interventions (e.g., legislation maki ng helmet use mandatory; school-based educational programs; community-based interventions) designed to increase bicycle helmet use be implemented. Wearing an approved helmet in the proper manner (taut chin strap, helmet shifted forward on the head, proper-fitting helmet) is the most effective way one can prevent serious head injury or death from a bicycle incident. Even a modest increase in helmet use rates can prove beneficial in reducing these rates.

Recommendations for future research

The studies presented here are conclusive in their findings with respect to helmet use and head injury. However, important future research in bicycle helmet effectiveness might examine the protective effect of helmets with mouth and face guards. Without addressing cost, a randomized controlled trial comparing facial injuries between those randomized to receive standard bicycle helmets and those randomized to receive helmets with face guards would be ideal. In its place, one might consider evaluating the same exposure - outcome relationship among individuals who already use such modified helmets such as competitive cyclists (long-distance bicyclists and BMX riders). The prevalence of these extended bicycle helmets is probably not high enough among everyday cyclists to make such a study feasible.

Review updated June 2001.