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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.
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