east pmg helmet efficacy 2010

CLINICAL MANAGEMENT UPDATE

An Evidence-Based Review: Helmet Efficacy to Reduce HeadInjury and Mortality in Motorcycle Crashes: EAST Practice

Management Guidelines

Jana B. A. MacLeod, MD, J. Christopher DiGiacomo, MD, Glen Tinkoff, MD, FACS, FCCM

According to the National Highway Traffic Safety Associa-tion, in 2008, 5,290 motorcyclists died and 96,000 were

injured. Motorcycles make up �3% of all registered vehicles inthe United States and account for only 0.4% of all vehiclemiles traveled. However, motorcycle crashes accounted for�10% of all motor vehicle crash fatalities, and per miletraveled, motor cycle crashes are �37 times more lethal thanautomobile crashes.

Head injuries are one of the most common injuries aftermotorcycle crashes and were estimated to be the cause ofdeath in �50% of these fatalities. In close to a third of thesevictims, the head injury is the sole organ system that isinjured. However, in the majority of patients, estimated ashigh as 90% of some patient cohorts, a head injury is presentalong with other injuries. Despite these facts, it is estimatedthat only 50% of motorcyclists routinely wear helmets.

It was intuitive even to our earliest ancestors that a hardshell would protect the head from injury. However, establishingthe effectiveness of the motorcycle helmet remains a challengingeffort especially in light of the powerful opposition to universalhelmet laws. Furthermore, quantifying the protective effect ofhelmets supports the promotion of helmet programs regardlessof the controversial nature of legislative efforts.

In the United States, an increasing recognition thathelmet use is associated with reductions in fatalities withoutapparent harm increased the implementation of universalhelmet laws. In response to the 1966 Federal Highway Act,which withheld federal funds from states that did not enact ahelmet law, Georgia became the first state to enact a manda-tory universal motorcycle helmet law in 1967. By 1975, 47 ofthe 50 states had universal helmet laws. However, public and

political concerns over individual rights versus public safetyopened a new debate. In the following years, politicalchanges reversed and/or limited previous sanctions and grantsthat encouraged states to enact universal helmet laws, whichfurther eroded support for helmet laws. An increasing numberof states either repealed their mandatory laws altogether orsignificantly reduced the laws to apply only to minors. Atpresent, only 20 states have universal helmet laws, another 26states require only partial coverage, and 4 states have nohelmet laws (Colorado, Illinois, Iowa, and New Hampshire).

A large volume of literature has quantified the conse-quences of not wearing a helmet while riding a motorcycle.Although motorcycle riding and registration are increasingand more states with universal helmet laws are introducingbills to repeal their laws, the debate continues on the personaladvantages of helmet usage. Therefore, we have reviewed theliterature and summarize the evidence basis for the use ofmotorcycle helmets. In particular, we have sought to assessthe impact of helmet use on overall mortality, head injury-related mortality, nonlethal head injury after a motorcyclecrash, and the impact universal helmet laws on helmet use.

STATEMENT OF PROBLEMMotorcycles are a significant cause of injury-related

fatality and disability. In particular, head injury is a commonassociated cause of death and long-term disability after amotorcycle crash. Despite these facts, there remains an on-going controversy as to the survival and disability advantagesfor riders who wear motorcycle helmets. In the public andlegislative sectors, there remains a significant policy contro-versy resulting in a push to retain partial coverage helmetlaws and to repeal universal helmet laws in many others.

QUESTIONS TO BE ADDRESSED

A. Do nonhelmeted riders in comparison with helmetedriders have a higher or lower overall death rate after amotorcycle crash?

B. Do nonhelmeted riders in comparison with helmeted rid-ers incur higher or lower rates of lethal head injury aftera motorcycle crash?

C. Do nonhelmeted riders in comparison with helmeted rid-ers incur higher or lower rates of nonlethal head injury oris the nonlethal head injury more or less severe after amotorcycle crash?

Submitted for publication March 11, 2010.Accepted for publication August 22, 2010.Copyright © 2010 by Lippincott Williams & WilkinsFrom the Department of Surgery (J.B.A.M.), Grady Hospital, Emory University

School of Medicine, Atlanta, Georgia; The Port Authority Heroes of September11 Trauma Center (J.C.D.), Jersey City Medical Center, Jersey City, New Jersey;and Department of Surgery (G.T.), Christiana Care Health System, Wilmington,Delaware.

Presented at the 23rd Annual Meeting of the Eastern Association for the Surgeryof Trauma, January 19–23, 2010, Phoenix, Arizona.

Supported and commissioned by Injury Control and Violence Prevention Committee,Eastern Association for the Surgery of Trauma.

Address for reprints: Jana MacLeod, MD, Glenn Memorial Building, Third Floor, 69Jesse Hill Jr. Drive, SE, Atlanta, GA 30303; email: [email protected].

DOI: 10.1097/TA.0b013e3181f8a9cc

The Journal of TRAUMA® Injury, Infection, and Critical Care • Volume 69, Number 5, November 2010 1101

D. Do geographical areas (i.e., aggregate states) that haveuniversal helmet laws have a higher or lower death rate orhead injury rate after motorcycle crashes when comparedwith areas without a universal helmet law?

METHODS AND PROCESSA computerized search of the world’s literature was

undertaken using PubMed, of the US National Library ofMedicine, extending back to 1990 to the present (2009) usingthe key words: helmet � (motorcycle OR crash). There were507 citations identified. The abstract for each was reviewed,and 197 candidate articles having possible applicability to theguideline topic were retrieved and reviewed. General re-views, letters to the editor, single case reports, and retrospec-tive reviews of poor quality were excluded. This left 45articles that were felt to have sufficient merit to form the basisfor the guidelines (Table 1). The articles were reviewed indetail by the authors J.M., G.H.T., and J.C.D.

Over the past decades, the volume of literature supportinghelmet usage prevents, and ethically so, any randomized controltrials or even controlled trials of helmet usage. Therefore, themost robust studies published in the past 20 years are predom-inantly prospective and retrospective epidemiologic studies. Asthere are no class I studies to review, the studies we did reviewdo not vary across the classes of evidence in a useful manner.Therefore, we categorized the articles in this review by studydesign. There are prospective cohort and cross-sectional studies.However, the majority of the studies are retrospective, eitherbefore and after cross-sectional studies of helmet law changes orcross-sectional studies of helmeted in comparison with nonhel-meted riders. Finally, we also identified case-control studies.

RECOMMENDATIONS

Level IAll motorcyclists should wear motorcycle helmets

when riding motorcycles to reduce the incidence of headinjury and severe head injury after a crash.

NB: This statement was made a level recommendationdespite a lack of class I data because of the volume of consistentclass II data, including robust prospective data, to support thisfinding without any methodologically similar data to refute it.

Level IIAll motorcyclists should wear motorcycle helmets

when riding motorcycles to improve overall survival andreduce head injury-related mortality after a crash.

Mandatory universal motorcycle helmet laws should beintroduced or reenacted to reduce mortality and head injuryafter a crash.

SCIENTIFIC FOUNDATIONThe evidence reviewed here that assesses the effective-

ness of helmets for motorcyclists comes from the following45 study designs:

1. Prospective cohort study of motorcycle riders.12. Prospective cross-sectional studies that compare helmeted

riders with nonhelmeted riders for different outcomes.2–5

3. Retrospective before and after cross-sectional studies inwhich outcomes of motorcycle crashes are compared be-fore and after either the repeal of or the enactment of amandatory universal helmet law.6–24

4. Case-control studies of motorcycle riders.25–27

5. Retrospective cross-sectional studies that compare hel-meted riders with nonhelmeted riders across differentoutcomes.28–43

6 Comparison of mortality between states with helmet lawsand states without helmet laws.44,45

The outcomes reported included any one or more of thefollowing: mortality, head injury-related mortality, preva-lence of head injury, and prevalence of severe head injury.

Do Nonhelmeted Riders in Comparison WithHelmeted Riders Have a Higher or LowerOverall Death Rate After a Motorcycle Crash?

Two prospective cross-sectional studies showed a re-duction in mortality for helmeted riders in comparison withnonhelmeted riders, with an odds ratio (OR) of 0.40 and 0.22,respectively.2,5 However, Kelley’s sample size was not ade-quate to reach statistical significance, and therefore, no deathreduction can be concluded from this study. Nine retrospec-tive cross-sectional studies reported mortality as an outcome,but two showed no reduction35,42 while seven showed reduc-tions that varied from a maximal OR estimate of 0.2933 to aminimal OR estimate of 0.84.28 Of the studies that showed amortality reduction, only three were adjusted for rider and/orenvironmental factors.28,33,34

There were five studies that compared crashes beforeand after helmet law repeal. Two of the studies showed anincrease in fatality after repeal of the helmet law, 26% and30% increases, respectively.8,10 However, two further studieshad nonsignificant increases in the ORs of death: OR of 1.087

(per 10,000 motorcycle registrations) and OR of 1.019 (per1,000 crashes). Interestingly, although the study of Bledsoeand Li did not show an overall reduction in mortality, therewas a significant increase in riders who were blood alcoholpositive at the time of the crash and who were also notwearing a helmet after the repeal when compared with before(14.2% vs. 33.6%, OR: 2.37, p � 0.05).

There were 12 studies that compared crashes before andafter helmet law establishment or reenactment. Auman et al.showed close to a halving of the relative risk (RR) of fatalityafter the law was reenacted (RR: 0.51, 9.3 fatalities per10,000 motorcycle registrations to 4.7 fatalities per 10,000registrations). Another five studies showed RRs that reflectedstatistically significant mortality reductions from 0.57 to0.81.15,21–24 One study, by Chiu et al., showed no change inmortality during the study period (4.0%).

Do Nonhelmeted Riders in Comparison WithHelmeted Riders Incur Higher or Lower Ratesof Lethal Head Injury After a MotorcycleCrash?

The RR of head injury-related mortality was reduced bymore than half after the enactment of a helmet law in Texasfrom 6.8 fatalities to 3.1 fatalities per 10,000 motorcycle

MacLeod et al. The Journal of TRAUMA® Injury, Infection, and Critical Care • Volume 69, Number 5, November 2010

© 2010 Lippincott Williams & Wilkins1102

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The Journal of TRAUMA® Injury, Infection, and Critical Care • Volume 69, Number 5, November 2010 Helmet Efficacy to Reduce Head Injury and Mortality

© 2010 Lippincott Williams & Wilkins 1103

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tien

tsw

ere

revi

ewed

,in

clud

ing

129

deat

hs.

Whe

nco

mpa

red

wit

hth

epr

elaw

peri

od,

head

inju

ries

decr

ease

d41

.4%

and

mot

orcy

cle-

rela

ted

deat

hsde

crea

sed

20.8

%

IIS

erva

dei

etal

.12

Eff

ect

ofIt

aly’

sm

otor

cycl

ehe

lmet

law

ontr

aum

atic

brai

nin

juri

es

Inj

Pre

v.20

03;9

:25

7–26

0R

etro

spec

tive

revi

ewof

trau

mat

icbr

ain

inju

ries

ata

regi

onal

neur

osur

gery

refe

rral

cent

erfo

r1

year

befo

rean

daf

ter

impl

emen

tati

onof

aun

iver

sal

mot

orcy

cle

helm

etla

w.

The

rew

asa

redu

ctio

nfr

om63

to43

per

100,

000

regi

stra

tion

sin

head

inju

ry-r

elat

edad

mis

sion

s.T

here

was

also

a76

%de

crea

sein

the

diag

nose

sof

trau

mat

icsu

bara

chno

idhe

mor

rhag

e,su

bdur

alhe

mat

oma,

and

epid

ural

hem

atom

aaf

ter

the

enac

tmen

tof

the

law

IIC

hris

tian

etal

.13

Mot

orcy

cle

helm

ets

and

head

inju

ries

inK

entu

cky

1995

–20

00

JK

yM

edA

ssoc

.20

03;1

01:2

1–26

Ret

rosp

ecti

vere

view

ofhe

adin

jury

and

head

inju

ryse

veri

tyaf

ter

am

otor

cycl

ecr

ash

from

asi

ngle

Lev

elI

trau

ma

cent

erfr

om19

95to

2000

.O

fno

te,

Ken

tuck

yre

peal

edth

eir

helm

etla

win

1998

.A

nonh

elm

eted

ride

rw

as4.

33m

ore

like

lyto

sust

ain

ahe

adin

jury

than

ahe

lmet

edri

der,

and

they

wer

eal

so4.

36m

ore

like

lyto

sust

ain

ase

vere

head

inju

ryth

anno

nhel

met

edri

ders

IIA

uman

etal

.14

Aut

opsy

stud

yof

mot

orcy

clis

tfa

tali

ties

:th

eef

fect

ofth

e19

92M

aryl

and

mot

orcy

cle

helm

etus

ela

w

Am

JP

ubli

cH

ealt

h.20

02;9

2:13

52–

1355

Ret

rosp

ecti

veco

mpa

riso

nof

mot

orcy

cle

fata

liti

esin

Mar

ylan

dfo

r33

mo

befo

rean

daf

ter

impl

emen

tati

onof

aun

iver

sal

helm

etla

w.

61.3

%of

fata

liti

esoc

curr

edbe

fore

the

law

was

enac

ted

and

38.7

%af

ter.

The

fata

lity

rate

per

10,0

00re

gist

rati

ons

decr

ease

dfr

om9.

32to

4.7

per

10,0

00m

otor

cycl

ere

gist

rati

ons

inth

e3-

yrpe

riod

befo

rean

daf

ter

the

enac

tmen

t



TAB

LE1.

Refe

renc

es:

Cita

tion

and

Sum

mar

yfo

rEB

RA

rtic

les

onth

eEf

ficac

yof

Mot

orcy

cle

Hel

met

s19

90–2

009

(con

tinue

d)

Cla

ssA

utho

rsT

itle

Cit

atio

nSu

mm

ary

IIF

erra

ndo

etal

.15

Impa

ctof

ahe

lmet

law

on2

whe

elm

otor

vehi

cle

cras

hm

orta

lity

ina

sout

hern

Eur

opea

nur

ban

area

Inj

Pre

v.20

00;6

:18

4–18

8R

etro

spec

tive

stud

yco

mpa

ring

the

2-yr

peri

odbe

fore

and

afte

rim

plem

enta

tion

ofa

univ

ersa

lm

otor

cycl

ehe

lmet

law

inS

pain

.D

ata

wer

eco

mpi

led

from

the

Med

ical

Exa

min

er,

poli

cere

cord

s,an

dth

eT

raffi

cA

utho

rity

ofB

arce

lona

.A

nnua

lfa

tali

ties

decr

ease

dfr

om60

inth

efi

rst

year

ofth

ere

view

to32

inth

ela

stye

ar,

wit

hth

ecr

ash

mor

tali

tyra

tede

crea

sing

from

6.9

to5.

2pe

r1,

000

cras

hes.

The

auth

ors

esti

mat

edth

at35

live

sw

ere

save

din

Bar

celo

nadu

ring

the

firs

t2

yrof

the

mot

orcy

cle

helm

etla

w

IIC

hiu

etal

.16

The

effe

ctof

the

Tai

wan

mot

orcy

cle

helm

etus

ela

won

head

inju

ries

Am

JP

ubli

cH

ealt

h.20

00;9

0:79

3–79

6R

etro

spec

tive

stud

yco

mpa

ring

mot

orcy

cle-

rela

ted

head

inju

ries

seen

at56

maj

orho

spit

als

acro

ssT

aiw

anfo

r1

year

befo

rean

daf

ter

impl

emen

tati

onof

aun

iver

sal

helm

etla

w,

base

don

the

Hea

dIn

jury

Reg

istr

yof

Tai

wan

.T

otal

num

ber

ofm

otor

cycl

e-re

late

dhe

adin

juri

esde

crea

sed

to33

%.

Inho

spit

alde

ath

rate

sre

mai

ned

unch

ange

dat

4.0%

IIT

sai

and

Hem

enw

ay17

Eff

ect

ofth

em

anda

tory

helm

etla

win

Tai

wan

Inj

Pre

v.19

99;5

:29

0–29

1R

etro

spec

tive

revi

ewin

thre

eci

ties

com

pari

ng6

mo

befo

reto

6m

oaf

ter

enac

tmen

tof

am

anda

tory

mot

orcy

cle

law

inT

aiw

an.

Fat

alit

ies

afte

ra

cras

hde

crea

sed

by14

%an

dhe

ad-r

elat

edfa

tali

ties

redu

ced

by22

%

IIP

eek-

Asa

and

Kra

us18

Est

imat

esof

inju

ryim

pair

men

taf

ter

acut

etr

aum

atic

inju

ryin

mot

orcy

cle

cras

hes

befo

rean

daf

ter

pass

age

ofa

man

dato

ryhe

lmet

use

law

Ann

Em

erg

Med

.19

97;2

9:63

0–63

6R

etro

spec

tive

revi

ewco

mpa

ring

4,79

0no

nfat

ally

inju

red

mot

orcy

cle

ride

rsfo

r1

year

befo

rean

daf

ter

enac

tmen

tof

the

Cal

ifor

nia

man

dato

rym

otor

cycl

ela

w,

link

ing

med

ical

reco

rds

topo

lice

repo

rts.

The

risk

ofa

head

inju

ry-r

elat

edim

pair

men

taf

ter

acr

ash

doub

led

whe

nno

tw

eari

nga

helm

etin

both

adju

sted

and

unad

just

edm

odel

s.T

hem

odel

sad

just

edfo

ral

coho

l,sp

eedi

ng,

gend

er,

and

bein

gth

row

nfr

omth

em

otor

cycl

e

IIK

raus

and

Pee

k19

The

impa

ctof

two

rela

ted

prev

enti

onst

rate

gies

onhe

adin

jury

redu

ctio

nam

ong

nonf

atal

lyin

jure

dm

otor

cycl

eri

ders

,C

alif

orni

a,19

91–1

993

JN

euro

trau

ma.

1995

;12:

873–

881

Ret

rosp

ecti

vere

view

ofno

nfat

ally

inju

red

mot

orcy

cle

ride

rsbe

fore

and

afte

ren

actm

ent

ofth

eC

alif

orni

am

anda

tory

mot

orcy

cle

helm

etla

wof

1992

.T

hela

wre

sult

edin

85.6

%of

the

inju

red

ride

rsw

eari

nga

helm

et.

Hea

din

juri

esde

crea

sed

from

38.2

%of

the

inju

ries

seen

befo

reth

een

actm

ent

to24

.1%

ofth

ehe

adin

juri

esaf

ter

the

law

was

enac

ted

IIP

anic

haph

ongs

eet

al.2

0

Eff

ects

ofla

wpr

omul

gati

onfo

rco

mpu

lsor

yus

eof

prot

ecti

vehe

lmet

son

deat

hfo

llow

ing

mot

orcy

cle

acci

dent

s

JM

edA

ssoc

Tha

i.19

95;7

8:52

1–52

5R

etro

spec

tive

revi

ewco

mpa

ring

the

2yr

befo

rean

daf

ter

impl

emen

tati

onof

am

otor

cycl

ehe

lmet

law

.D

espi

tea

24%

incr

ease

inm

otor

cycl

ecr

ash

inju

ries

,de

aths

decr

ease

dfr

om2%

to1.

4%.

The

perc

enta

geof

pati

ents

who

died

beca

use

ofbr

ain

inju

ryre

mai

ned

cons

tant

duri

ngth

e4-

yrpe

riod

,ra

ngin

gfr

om81

%to

86%

IIM

ock

etal

.21

Inju

rypr

even

tion

stra

tegi

esto

prom

ote

helm

etus

ede

crea

sese

vere

head

inju

ries

ata

Lev

elI

trau

ma

cent

er

JT

raum

a.19

95;3

9:29

–35

Ret

rosp

ecti

vere

view

ofth

etr

aum

are

gist

ryof

aL

evel

Itr

aum

ace

nter

over

8yr

com

pari

nghe

lmet

edto

nonh

elm

eted

mot

orcy

cle

ride

rs.

Aun

iver

sal

mot

orcy

cle

helm

etla

ww

asen

acte

ddu

ring

the

revi

ewpe

riod

.T

hem

orta

lity

rate

decr

ease

dfr

om10

%be

fore

enac

tmen

tof

the

helm

etla

wto

6%af

ter,

and

seve

rehe

adin

jury

decr

ease

dfr

om20

%of

cras

had

mis

sion

sto

9%

IIK

raus

etal

.22

The

effe

ctof

the

1992

Cal

ifor

nia

mot

orcy

cle

helm

etus

ela

won

mot

orcy

cle

cras

hfa

tali

ties

and

inju

ries

JAM

A.

1994

;272

:15

06–1

511

Ret

rosp

ecti

vere

view

ofal

lm

otor

cycl

efa

tali

ties

for

the

year

befo

rean

daf

ter

impl

emen

tati

onof

am

anda

tory

mot

orcy

cle

helm

etla

w,

base

don

deat

hce

rtifi

cate

san

dpo

lice

repo

rts.

The

rew

asa

37.5

%de

crea

sein

abso

lute

num

ber

offa

tali

ties

stat

ewid

edu

ring

the

firs

tye

araf

ter

enac

tmen

tan

dw

ith

ade

crea

sein

the

fata

lity

rati

ofr

om70

.1to

51.5

fata

liti

espe

r10

0,00

0re

gist

rati

ons

inC

alif

orni

a

IIF

lem

ing

and

Bec

ker2

3

The

impa

ctof

the

Tex

as19

89m

otor

cycl

ehe

lmet

law

onto

tal

and

head

—re

late

dfa

tali

ties

,se

vere

inju

ries

,an

dov

eral

lin

juri

es

Med

Car

e.19

92;3

0:83

2–84

5R

etro

spec

tive

revi

ewof

all

mot

orcy

cle

fata

liti

esin

Tex

asfr

om19

84th

roug

h19

90,

wit

ha

helm

etla

wbe

ing

enac

ted

in19

89.

Ove

rall

mor

tali

tyre

duce

dfr

om12

.1to

9.8

per

10,0

00re

gist

rati

ons.

As

ape

rcen

tage

ofth

eto

tal

annu

alde

aths

,he

ad-r

elat

edfa

tali

ties

decr

ease

dfr

om56

%to

31.5

%



TAB

LE1.

Refe

renc

es:

Cita

tion

and

Sum

mar

yfo

rEB

RA

rtic

les

onth

eEf

ficac

yof

Mot

orcy

cle

Hel

met

s19

90–2

009

(con

tinue

d)

Cla

ssA

utho

rsT

itle

Cit

atio

nSu

mm

ary

IIM

uell

eman

etal

.24

Mot

orcy

cle

cras

hin

juri

esan

dco

sts:

effe

ctof

are

enac

ted

com

preh

ensi

vehe

lmet

use

law

Ann

Em

erg

Med

.19

92;2

1:26

6–27

2R

etro

spec

tive

revi

ewof

1ye

arbe

fore

and

afte

rth

ere

enac

tmen

tof

the

mot

orcy

cle

helm

etla

win

Neb

rask

a.B

oth

regi

stra

tion

san

dcr

ashe

sre

duce

din

this

sam

eti

me

peri

odof

1987

–198

9.T

heov

eral

lde

ath

rate

drop

ped

from

13to

8pe

r10

,000

regi

stra

tion

s.T

hefr

eque

ncy

and

seve

rity

ofbr

ain

inju

ryw

ere

sim

ilar

for

the

two

tim

epe

riod

s

Cas

e-co

ntro

lst

udie

s

IIN

orve

llan

dC

umm

ings

25

Ass

ocia

tion

ofhe

lmet

use

wit

hde

ath

inm

otor

cycl

ecr

ashe

s:a

mat

ched

-pai

rco

hort

stud

y

Am

JE

pide

mio

l.20

02;1

56:4

83–

487

Mat

ched

pair

coho

rtst

udy

usin

gth

eN

HT

SA

-FA

RS

data

base

for

fata

liti

esw

ithi

n30

dof

the

cras

hth

atoc

curr

edfr

om19

80to

1998

.60

.8%

ofth

efa

tali

ties

invo

lved

nonh

elm

eted

ride

rs.

The

RR

ofde

ath

for

ahe

lmet

edri

der

was

esti

mat

edto

be0.

61co

mpa

red

wit

ha

nonh

elm

eted

ride

r,co

ntro

llin

gfo

rm

otor

cycl

ean

dcr

ash-

rela

ted

vari

able

s,ag

e,ge

nder

,an

dse

atpo

siti

on

IIT

sai

etal

.26

Cas

e-co

ntro

lst

udy

ofth

eef

fect

iven

ess

ofdi

ffer

ent

type

sof

helm

ets

for

the

prev

enti

onof

head

inju

ries

amon

gm

otor

cycl

eri

ders

inT

aipe

i,T

aiw

an

Am

JE

pide

mio

l.19

95;1

42:9

74–

981

Mot

orcy

cle

ride

rscr

ash

adm

issi

ons

in15

hosp

ital

sin

Tai

pei,

Tai

wan

for

3m

oin

1990

.C

ases

wer

ehe

ad-i

njur

edm

otor

cycl

ecr

ash

vict

ims.

Con

trol

sw

ere

mot

orcy

cle

cras

hvi

ctim

sw

ith

inju

ries

othe

rth

anhe

ad.

Str

eet

cont

rols

wer

eno

ninj

ured

mot

orcy

cle

ride

rsph

otog

raph

edco

ntem

pora

neou

sly

toin

jure

dco

ntro

ls.

Hea

din

jury

was

invo

lved

in41

.5%

ofth

e1,

351

inju

ries

duri

ngth

est

udy

peri

od

IIG

abel

laet

al.2

7R

elat

ions

hip

ofhe

lmet

use

and

head

inju

ries

amon

gm

otor

cycl

ecr

ash

vict

ims

inE

lP

aso

coun

ty,

Col

orad

o,19

98–1

990

Acc

idA

nal

Pre

v.19

95;2

7:36

3–36

9A

coun

ty-b

ased

stud

yof

head

inju

ryaf

ter

mot

orcy

cle

cras

hes

dete

rmin

edby

traf

fic

acci

dent

repo

rts

and

the

inju

ryep

idem

iolo

gypr

ogra

mof

Col

orad

o.A

case

was

am

otor

cycl

eri

der

wit

ha

head

inju

ryaf

ter

acr

ash

ina

2-yr

peri

odof

tim

efr

om19

89to

1990

.A

cont

rol

was

am

otor

cycl

ecr

ash

inth

esa

me

coun

tyan

dti

me

peri

odbu

tw

itho

uta

head

inju

ry.

Not

wea

ring

ahe

lmet

incr

ease

dth

eli

keli

hood

ofa

head

inju

ryfr

oma

cras

hby

anod

dsra

tio

of3.

34re

lati

veto

thos

eri

ders

wea

ring

ahe

lmet

Ret

rosp

ecti

vecr

oss-

sect

iona

lst

udie

s

III

Cro

ceet

al.

28

Impa

ctof

mot

orcy

cle

helm

ets

and

stat

ela

ws

onso

ciet

y’s

burd

en:

Ana

tion

alst

udy

Ann

Surg

.20

09;2

50:

390–

394

Ret

rosp

ectiv

ere

view

from

2002

to20

07of

Nat

iona

lT

raum

aD

ata

Ban

k.H

elm

eted

trau

ma

patie

nts

had

low

erod

dsof

deat

hw

hen

com

pare

dw

ithno

nhel

met

ed:

adju

sted

odds

ratio

of0.

84(9

5%C

I:0.

76–0

.93)

.N�

75,6

44he

lmet

edpa

tient

sha

dbe

tter

Gla

sgow

Com

aSc

ale

scor

es

III

Gos

lar

etal

.29

Hel

met

use

and

asso

ciat

edsp

inal

frac

ture

sin

mot

orcy

cle

cras

hvi

ctim

s

JT

raum

a20

08;6

4:19

0–19

6R

etro

spec

tive

revi

ewof

trau

ma

regi

stry

ofon

eL

evel

Itr

aum

ace

nter

from

July

1,20

02,

toJu

ne30

,20

05.

Non

helm

eted

ride

rw

as2

tim

esm

ore

like

lyto

sust

ain

abr

ain

inju

ryan

d3

tim

esm

ore

like

lyto

die

from

the

cras

hth

ana

helm

eted

ride

r

III

Hou

ston

and

Ric

hard

son4

4

Mot

orcy

cle

safe

tyan

dth

ere

peal

ofun

iver

sal

helm

etla

ws

Am

JP

ubli

cH

ealt

h.20

07;9

7:20

63–

2069

Ret

rosp

ecti

vere

view

ofal

l51

stat

esfr

omth

eN

HT

SA

Fat

alA

ccid

ent

Rep

orti

ngS

yste

mfr

om19

75to

2004

.M

orta

lity

was

anal

yzed

cont

roll

ing

for

othe

rri

ders

and

stat

efa

ctor

sth

ataf

fect

mot

orcy

cle-

rela

ted

mor

tali

ty:

dem

ogra

phic

,so

cial

,tr

affi

csa

fety

,an

dpo

pula

tion

dens

ity

acro

ssst

ates

.T

here

was

a13

.7%

mor

tali

tyre

duct

ion

inst

ates

attr

ibut

able

toun

iver

sal

helm

etla

w



TAB

LE1.

Refe

renc

es:

Cita

tion

and

Sum

mar

yfo

rEB

RA

rtic

les

onth

eEf

ficac

yof

Mot

orcy

cle

Hel

met

s19

90–2

009

(con

tinue

d)

Cla

ssA

utho

rsT

itle

Cit

atio

nSu

mm

ary

III

Cob

enet

al.4

5C

hara

cter

isti

csof

mot

orcy

cle-

rela

ted

hosp

ital

izat

ions

:co

mpa

ring

stat

esw

ith

diff

eren

the

lmet

law

s

Acc

idA

nal

Pre

v.20

07;3

9:19

0–19

6A

1ye

arre

tros

pect

ive

revi

ewof

the

Hea

lthc

are

Cos

tan

dU

tili

zati

onP

roje

ct(H

CU

P)

regi

stry

.T

heH

CU

Pst

ate

inpa

tien

tda

taba

se(S

ID)

cont

ains

data

from

33st

ates

and

capt

ures

�80

%of

all

hosp

ital

disc

harg

esin

the

Uni

ted

Sta

tes.

25,7

94ca

ses

wer

eid

enti

fied

;16

,105

from

stat

esw

ith

univ

ersa

lhe

lmet

law

s,7,

924

from

stat

esw

ith

part

ial

law

s,an

d1,

765

from

stat

esw

ith

nohe

lmet

law

s.C

ases

from

stat

esw

itho

utun

iver

sal

helm

etla

ws

wer

e52

%m

ore

like

lyto

sust

ain

the

mos

tse

vere

form

sof

trau

mat

icbr

ain

inju

ry(R

R:

1.52

)an

dha

da

mor

tali

tyra

te39

%hi

gher

than

thos

est

ates

wit

hun

iver

sal

helm

et

III

Lin

etal

.30

Sur

vey

oftr

aum

atic

intr

acra

nial

hem

orrh

age

inT

aiw

an

Surg

Neu

rol.

2006

;66

:S20

–S25

Ret

rosp

ecti

vere

view

of90

,250

head

trau

ma

case

adm

itte

dto

the

hosp

ital

inT

aiw

an,

excl

udin

gde

adon

arri

vals

and

outp

atie

nts

duri

ngan

8-yr

peri

od.

47%

ofal

lin

juri

esw

ere

mot

orcy

cle

rela

ted.

Tho

seno

tw

eari

nga

helm

etha

da

32.9

%in

cide

nce

ofin

trac

rani

alhe

mor

rhag

eco

mpa

red

wit

h25

.2%

for

thos

ew

how

ere.

The

chan

ceof

havi

ngan

intr

acra

nial

hem

orrh

age

was

1.4

tim

eshi

gher

for

thos

eno

tw

eari

nga

helm

etco

mpa

red

wit

hth

ose

who

did

(odd

sra

tio

of1.

40)

III

Eas

trid

geet

al.3

1

Eco

nom

icim

pact

ofm

otor

cycl

ehe

lmet

s:fr

omim

pact

todi

scha

rge

JT

raum

a.20

06;6

0:97

8–98

4M

otor

cycl

ists

who

cras

hed

and

foun

din

NH

TS

AG

ES

data

base

for

preh

ospi

tal

data

and

NT

DB

for

hosp

ital

data

from

1994

to20

02.

The

rew

asle

ssth

anha

lfth

eri

skof

deat

hor

adm

issi

onw

ith

ahe

adin

jury

for

helm

eted

ride

rsin

com

pari

son

tono

nhel

met

edri

ders

III

Javo

uhey

etal

.32

Inci

denc

ean

dri

skfa

ctor

sof

seve

retr

aum

atic

brai

nin

jury

resu

ltin

gfr

omro

adac

cide

nts:

apo

pula

tion

-ba

sed

stud

y

Acc

idA

nal

Pre

v.20

06;3

8:22

5–23

3M

otor

cycl

ecr

ashe

sw

ere

iden

tifi

edin

apo

pula

tion

-bas

edro

adtr

aum

are

gist

ryin

Fra

nce

from

1996

to20

01to

dete

rmin

eri

sks

for

seve

rehe

adin

jury

.A

nonh

elm

eted

ride

rha

dan

18-f

old

high

erri

skof

havi

nga

seve

rehe

adin

jury

asde

fine

dby

AIS

scor

e2

orhi

gher

asco

mpa

red

wit

hhe

lmet

edri

ders

III

Nak

ahar

aet

al.3

3

Tem

pora

ldi

stri

buti

onof

mot

orcy

clis

tin

juri

esan

dri

skof

fata

liti

esin

rela

tion

toag

e,he

lmet

use,

and

ridi

ngw

hile

into

xica

ted

inK

hon

Kae

n,T

hail

and

Acc

idA

nal

Pre

v.20

05;3

7:83

3–84

2R

etro

spec

tive

revi

ewof

9,55

2pa

tien

tsin

jure

din

mot

orcy

cle

cras

hes

inT

hail

and

and

tran

sfer

red

toth

ere

gion

alm

edic

alce

nter

over

5yr

.T

heca

sefa

tali

tyra

tew

as0.

25fo

rhe

lmet

edri

ders

and

0.94

for

nonh

elm

eted

ride

rs.

The

fata

lity

was

also

stra

tifi

edby

alco

hol

into

xica

tion

and

tim

eof

day

ofcr

ash

III

Hun

dley

etal

.34

Non

-hel

met

edm

otor

cycl

ists

:a

burd

ento

soci

ety?

Ast

udy

usin

gth

eN

atio

nal

Tra

uma

Dat

aba

nk

JT

raum

a.20

04;5

7:94

4–94

9R

etro

spec

tive

revi

ewof

mot

orcy

clis

tcr

ashe

sid

enti

fied

inth

eN

TD

Bfr

om19

94to

2002

.T

heri

skof

deat

hw

as44

%lo

wer

for

helm

eted

ride

rsth

anno

nhel

met

edri

ders

.69

.2%

ofal

lri

ders

wer

eli

sted

asw

eari

nga

helm

et

III

Bra

ndt

etal

.35

Hos

pita

lco

stis

redu

ced

bym

otor

cycl

ehe

lmet

use

JT

raum

a.20

02;5

3:46

9–47

1R

etro

spec

tive

revi

ewof

mot

orcy

cle

cras

hes

inth

etr

aum

are

gist

ryat

aL

evel

Itr

aum

ace

nter

from

1996

to20

00.

The

risk

ofde

ath

was

16%

low

erin

helm

eted

ride

rsas

com

pare

dw

ith

nonh

elm

eted

ride

rs



TAB

LE1.

Refe

renc

es:

Cita

tion

and

Sum

mar

yfo

rEB

RA

rtic

les

onth

eEf

ficac

yof

Mot

orcy

cle

Hel

met

s19

90–2

009

(con

tinue

d)

Cla

ssA

utho

rsT

itle

Cit

atio

nSu

mm

ary

III

Pee

k-A

saet

al.3

6

The

prev

alen

ceof

nons

tand

ard

helm

etus

ean

dhe

adin

juri

esam

ong

mot

orcy

cle

ride

rs

Acc

idA

nal

Pre

v.19

99;3

1:22

9–23

3R

etro

spec

tive

revi

ewco

mpa

ring

helm

ets

that

met

the

1992

Cal

ifor

nia

Man

dato

ryH

elm

etU

seL

awre

quir

emen

tsto

thos

ew

hich

did

not.

One

-th

ird

ofri

ders

who

secr

ash

repo

rtin

dica

ted

ano

nsta

ndar

dhe

lmet

wer

eki

lled

,co

mpa

red

wit

h15

.5%

onno

nhel

met

edri

ders

and

13.6

%of

helm

eted

ride

rs.

Am

ong

all

ride

rsw

eari

ngno

nsta

ndar

dhe

lmet

s,75

%su

stai

ned

ahe

adin

jury

ofan

yse

veri

tyan

d62

.5%

sust

aine

da

head

inju

ry�

3.T

his

was

also

sign

ifica

ntly

high

erth

anth

ose

ride

rsno

tw

eari

nga

helm

et(5

1.9%

and

37.4

%)

and

thos

ew

eari

nga

stan

dard

helm

et(3

0.7%

and

21.8

%).

The

auth

ors

conc

lude

that

nons

tand

ard

helm

ets

dono

tpr

ovid

epr

otec

tion

III

Pet

rido

uet

al.3

7F

atal

itie

sfr

omno

nuse

ofse

atbe

lts

and

helm

ets

inG

reec

e:a

nati

onw

ide

appr

aisa

l.H

elle

nic

Roa

d,tr

affi

cpo

lice

Acc

idA

nal

Pre

v.19

98;3

0:87

–91

Ret

rosp

ecti

vean

alys

isof

all

mot

orcy

cle

cras

hes

inG

reec

efo

r19

85an

d19

94.

No

mot

orcy

cle

law

sw

ere

inef

fect

duri

ngei

ther

peri

od,

and

helm

etus

era

tes

wer

esi

mil

arfo

rtw

ope

riod

s.In

1985

,3.

5%of

helm

eted

ride

rsdi

edin

mot

orcy

cle

cras

hes

com

pare

dw

ith

4.3%

ofun

helm

eted

ride

rs.

In19

94,

2.9%

ofth

ehe

lmet

edri

ders

died

inm

otor

cycl

ecr

ashe

sco

mpa

red

wit

h5.

1%of

the

unhe

lmet

edri

ders

.T

heau

thor

ses

tim

ate

that

38%

ofal

lm

otor

cycl

ede

aths

coul

dpo

tent

iall

ybe

avoi

ded

ifal

lm

otor

cycl

eri

ders

wor

ehe

lmet

s

III

Row

land

etal

.38

Mot

orcy

cle

helm

etus

ean

din

jury

outc

ome

and

hosp

ital

izat

ion

cost

sfr

omcr

ashe

sin

Was

hing

ton

stat

e

Am

JP

ubli

cH

ealt

h.19

96;8

6:41

–45

Ret

rosp

ecti

vere

view

com

bini

ngst

ate

cras

hin

form

atio

n,ho

spit

alre

cord

s,an

dde

ath

reco

rds

for

1989

inW

ashi

ngto

nS

tate

.T

here

wer

e2,

090

cras

hes

wit

h59

fata

liti

es(2

.8%

).M

otor

cycl

eri

ders

who

wer

eho

spit

aliz

edaf

ter

acr

ash

wer

e2.

9ti

mes

mor

eli

kely

tobe

hosp

ital

ized

wit

ha

head

inju

ryan

d3.

7ti

mes

mor

eli

kely

toha

vesu

ffer

eda

seve

reof

crit

ical

head

inju

ryif

they

wer

eno

tw

eari

nga

helm

et.

Non

helm

eted

ride

rsha

d1.

62ti

mes

the

risk

ofa

fata

lcr

ash

com

pare

dw

ith

the

helm

eted

ride

rs

III

Ors

ayet

al.3

9M

otor

cycl

etr

aum

ain

the

Sta

teof

Illi

nois

:an

alys

isof

the

Illi

nois

depa

rtm

ent

ofpu

blic

heal

thtr

aum

are

gist

ry

Ann

Em

erg

Med

.19

95;2

8:45

5–46

0R

etro

spec

tive

revi

ewof

the

Illi

nois

trau

ma

regi

stry

for

18m

oco

mpa

ring

helm

eted

wit

hun

helm

eted

mot

orcy

cle

ride

rs.

Of

1,23

1,18

%w

ere

helm

eted

and

56%

wer

eno

t.30

%of

the

helm

eted

ride

rssu

stai

ned

head

inju

ries

com

pare

dw

ith

51%

for

unhe

lmet

edri

ders

.T

heun

helm

eted

ride

rsal

soha

dm

ore

seve

rehe

adin

juri

es

III

Rut

ledg

ean

dS

tutt

s40

The

asso

ciat

ion

ofhe

lmet

use

wit

hth

eou

tcom

eof

mot

orcy

cle

cras

hin

jury

whe

nco

ntro

llin

gfo

rcr

ash/

inju

ryse

veri

ty

Acc

idA

nal

Pre

v.19

93;2

5:34

7–35

3R

etro

spec

tive

anal

ysis

ofth

eN

orth

Car

olin

ast

ate

trau

ma

regi

stry

over

3.5

yr,

com

pari

ng89

2pa

tien

ts.

Hel

met

info

rmat

ion

was

avai

labl

efo

r46

0(5

1.6%

).H

ead

inju

ries

wit

hA

ISsc

ore

2to

5oc

curr

edin

53%

ofun

helm

eted

ride

rsco

mpa

red

wit

h28

%of

helm

eted

ride

rs

III

Bra

ddoc

ket

al.4

1

Apo

pula

tion

-bas

edst

udy

ofm

otor

cycl

ein

jury

and

cost

sA

nnE

mer

gM

ed.

1992

;21:

273–

278

Ret

rosp

ecti

vere

view

of11

2m

otor

cycl

ede

aths

inC

onne

ctic

utdu

ring

a2-

yrpe

riod

.T

hefa

tali

tyra

tefo

run

helm

eted

ride

rsw

as26

.7pe

r1,

000

cras

hes

com

pare

dw

ith

7.9

for

helm

eted

ride

rs

III

Off

ner

etal

.42

The

impa

ctof

mot

orcy

cle

helm

etus

eJ

Tra

uma.

1992

;32:

636–

642

Ret

rosp

ecti

vere

view

ofad

mit

ted

ride

rsaf

ter

mot

orcy

cle

cras

hat

one

Lev

elI

trau

ma

cent

er.

The

trau

ma

regi

stry

iden

tifi

edth

eca

ses

from

1985

to19

90.

Hea

din

jury

was

redu

ced

by68

%w

hen

wea

ring

ahe

lmet

,w

here

asth

ere

was

noim

pact

onde

ath

III

Sha

nkar

etal

.43

Hel

met

use,

patt

erns

ofin

jury

,m

edic

alou

tcom

ean

dco

sts

amon

gm

otor

cycl

edr

iver

sin

Mar

ylan

d

Acc

idA

nal

Pre

v.19

92;2

4:38

5–39

6R

etro

spec

tive

revi

ewof

all

mot

orcy

cle

cras

hes

inth

eS

tate

ofM

aryl

and

for

one

year

,19

87to

1988

.R

ider

sw

ore

ahe

lmet

in35

%of

the

cras

hes



registrations23 (RR: 2.19, p � 0.05). In Pennsylvania, afterthe repeal of the helmet law, the head injury-related death rateper 10,000 motorcycle registrations increased by 36.9%6 (1.6to 2.2 fatalities per 10,000 registrations, p � 0.05).

Do Nonhelmeted Riders in Comparison WithHelmeted Riders Incur Higher or Lower Ratesof Nonlethal Head Injury or Severity ofNonlethal Head Injury After a MotorcycleCrash?

All 25 of the studies that had prevalence of a nonfatalhead injury as an outcome had a significantly lower incidencefor helmeted riders, after reenactment or before repeal of ahelmet law. One of the prospective studies that observedmotorcycle riders to determine the incidence of head injury-associated crashes showed that nonhelmeted riders sustaineda head injury more than twice the rate of helmeted riders1

(4.7% vs. 1.9%). Three studies showed an ORs of a headinjury after a crash to vary from 2.3 times to 4.4 times higherfor nonhelmeted riders when compared with helmeted rid-ers3,4 (p � 0.05). Ouellet and Kasantikul showed an ORs ofsustaining a serious injury to be 3.5 times higher (p � 0.05)for nonhelmeted riders.

Retrospective studies confirm the consistent findings ofthe prospective studies that head injury is uniformly morefrequent and more severe when sustaining a crash without ahelmet. The magnitude of the increased prevalence of a headinjury after a nonhelmeted crash is as high as 4.3 times to alow of 1.7 times higher than after a helmeted crash in nineretrospective cross-sectional studies. However, for severehead injuries, most commonly defined as an AbbreviatedInjury Scale score �2, the magnitude of the estimate isuniformly larger. For three retrospective studies, the ORs ofa severe head injury were 18.1 (12.5–25.3), 4.4 (2.58–7.37),and 3.7 (1.9–7.3), respectively.13,32,38 Lin et al. showed a41% increase in trauma-induced brain hemorrhage, includingsubarachnoid, subdural, and epidural hematomas when a riderwas nonhelmeted during a crash.

The case-control studies showed an adjusted OR of0.26 (0.14–0.48) and 0.41 (0.21–0.81), which represents asignificant protective effect of wearing a helmet in reducingthe incidence of a head injury after a motorcycle crash.26,27 Infour retrospective studies in which universal motorcycle hel-met laws were enacted, the incidence of nonlethal head injurydecreased from 29% to reductions of 63%.

In one study in which the motorcycle law was repealed,the incidence of hospitalizations for head injury increased by42%, from 15.4 to 21.9 per 10,000 motorcycle registrations(p � 0.05).6

Do Geographical Areas (i.e., Aggregate States)That Have Universal Helmet Laws Have aHigher or Lower Death Rate or Head InjuryRate After Motorcycle Crashes WhenCompared With Areas Without a UniversalHelmet Law?

Two studies compared regions with and without helmetlaws. Houston and Richardson developed a model for motor-

cycle crash fatality as a function of the state’s helmet lawwhile controlling for minimal legal drinking age, partialversus full helmet laws, 0.08 blood alcohol concentrationlaw, roads with maximum speed limit of 65, daily temper-ature, daily percent precipitation, gender, age, per capitaincome, per capita alcohol consumption, and populationdensity. Their results showed 1.3 fewer fatalities per10,000 motorcycle registrations in helmet law states that canbe attributed in their model to the presence of the helmet law.Furthermore, using hospital discharge data from 33 states,Coben et al. calculated a RR of 0.65 (p � 0.05) and 0.72 (p �0.05), respectively, for severe head injury and fatalities instates with universal helmet laws when compared with stateswithout universal helmet laws.

STUDY LIMITATIONSThe main limitation of these uncontrolled and observa-

tional studies involves the collection and incorporation in theanalysis of potential confounders for the outcomes studied.The wearing of helmets is associated with multiple factors,many of which have also been shown to be associated withthe incidence and severity of crashes. Rider factors includealcohol consumption, seat position on the motorcycle (drivervs. passenger), age, and gender. There are also environmentalfactors such as weather, time of day; other policy factors suchas speed limits and DUI laws; and other intrinsic motorcyclefactors such as the size and type of motorcycle itself (thepotential kinetic energy of the crash) also contribute tomotorcycle crash occurrence and severity and ultimatelycrash consequences for the rider. Unfortunately, many ofthese factors are not easy to reliably measure on a crash-to-crash basis, and therefore, only nine studies, in part, adjustedfor at least a portion of these factors. There were other studiesthat stratified the study group by various factors but did notcontrol for them in their analysis. The majority of the studiesdid not control for any potential confounders. A secondmethodological concern is selection bias. The subjects inthese studies were not selected randomly, except for the onecohort study that chose the students randomly. There weremissing data, and no studies had information on those “notchosen” to confirm that they were the same as those includedin the study.

A large number of the studies reported fatalities andprevalence of head injuries as a rate, a function of either thenumber of motorcycle registrations or the number of crashes.This eliminates the misinterpretation of changes in absolutefatalities that reflect changes in the number of riders or thenumber of riders who crash. However, changes in registrationsmay not be an accurate denominator to reflect the active riderswho are engaging in motorcycle usage and, therefore, mayobscure difference. Perhaps, vehicle miles driven are a betterdenominator for this purpose for the same reason it is used inmotor vehicle collision fatality rates. A good example is inthe study by Bledsoe and Li, in which registrations decreasedand thereby crashes decreased, but the fatality rate increased.However, perhaps because of the decreases, the absoluteincrease seems minimal and statistically not significant.



The variation in helmet usage in these studies wassubstantial. Internationally, Conrad et al. reported that thehelmet usage was as high as 89% in Indonesia, whereasLaTorre et al. reported only a 12% rate of helmet usage inItaly. Nationally, in America, Brandt et al. reported in theirstudy from Michigan a prevalence of 80.5% of riders wearinga helmet during a crash, whereas a study conducted in Illinoisby Kelly et al. reported a 14.6% prevalence of helmets inriders involved in crashes. Without nonrandom selection ofthese studies, the variation in helmet usage can also impactthe results obtained.

The studies reviewed here discuss only the use ofhelmets. However, the issue of misuse as noted by Peek-Asaet al. in his 1999 study in Thailand can also be a major factorin postcrash injury. Further study is required to better under-stand and to quantify this problem. Furthermore, in thesestudies, we did not explore in depth the impact of partialhelmet laws, although the studies by Houston and Richardsonand Tsai SY attempted to address this issue. Interestingly,Houston and Richardson found that partial helmet lawsshowed no improvement in outcomes over states with nohelmet laws.

SUMMARY

A. The use of motorcycle helmets decreases the overall deathrate of motorcycle crashes when compared with nonhel-meted riders.

B. The use of motorcycle helmets decreases the incidence oflethal head injury in motorcycle crashes when comparedwith nonhelmeted riders.

C. The use of motorcycle helmets decreases the severity ofnonlethal head injury in motorcycle crashes when com-pared with nonhelmeted riders.

D. Mandatory universal helmet laws reduce mortality andhead injury in geographical areas with the law whencompared with areas without it.

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