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Head Injuries Associated with Motorcycle Use -- Wisconsin, 1991

From 1989 through 1991, a total of 9913 persons in the United States died as a result of crashes while operating or riding motorcycles (1). Although use of motorcycle helmets is an effective means for preventing crash-related fatal injuries (2), 25 states and the District of Columbia have not yet enacted laws requiring the universal use of motorcycle helmets (1). This report describes a study by the University of Wisconsin and the Wisconsin Department of Transportation in which linked police reports and hospital discharge records for 1991 were used to assess the risk for head injury for motorcyclists in motor-vehicle crashes, the initial inpatient hospital charges for motorcyclists with head injuries resulting from crashes, and the reduction in injuries and fatalities associated with universal helmet use.

For this report, motorcyclists were defined as persons who were operating or riding as a passenger on a motorcycle. Wisconsin was one of seven states funded under the Crash Outcome Data Evaluation Systems project of the National Highway Traffic Safety Administration to generate linked statewide data systems. Because personal identifiers were not available, Police Accident Reports from the Wisconsin Department of Transportation and inpatient discharge records for acute-care hospitals from the state's Office of the Commissioner of Insurance were linked through a probabilistic method (which calculates the likelihood that a police report and a discharge record represent the same person) using date of the event -- the crash or the hospital admission -- and the motorcyclist's birth date, sex, and zip code of residence. Secondary linking variables were the county of the event, the health service area of the event, the injury, and whether the person was transported by ambulance from the crash. Uncertain matches were reviewed manually using additional corroborating information, such as International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) external cause of injury codes and consistency with known patterns of trauma referral and injury resulting from motor-vehicle crashes. Approximately 7% of the matches made by computer between police reports and hospital records were incorrect.

Based on ICD-9-CM diagnostic codes in the discharge record, head injuries were classified into three mutually exclusive categories: 1) brain injury, defined as any diagnosis of intracranial injury with or without skull fracture, intracranial hemorrhage following injury, or loss of consciousness for 1 hour or more; 2) skull fracture with no intracranial injury; and 3) concussion with only brief (less than 1 hour) or no loss of consciousness.

Of the 3184 motorcyclists involved in police-reported crashes in Wisconsin in 1991, 2015 (63.3%) were unhelmeted and 994 (31.2%) were helmeted at the time of the crash. Helmet use was unknown for 175 (5.5%), four of whom were fatally injured; of 32 who were hospitalized, 13 incurred head injuries. Of those motorcyclists for whom helmet status was known, 545 were hospitalized and 74 died, including 55 who were unhelmeted and 19 who were helmeted. Of the 545 hospitalized, 187 (34.3%) had sustained a head injury (Table_1). Overall, unhelmeted motorcyclists involved in police-reported crashes were more than twice as likely to be hospitalized for a head injury (153 {7.6%}) than were helmeted riders (34 {3.4%}). Brain injury occurred among 97 (4.8%) of those who were unhelmeted and 17 (1.7%) of those who were helmeted (rate ratio {RR}=2.9, 95% confidence interval {CI}=1.7-4.9); the rate for skull fracture among unhelmeted riders (0.9%) was 4.5 times (95% CI=1.0-19.2) that among helmeted riders (0.2%). The rate for concussions among unhelmeted motorcyclists involved in crashes (1.9%) was higher than that for helmeted riders (1.5%) (RR=1.3; 95% CI=0.7-2.3).

Total initial * inpatient hospital charges for the 97 unhelmeted motorcyclists with brain injuries was $2,396,366 -- compared with $333,619 for the 17 helmeted motorcyclists with brain injuries (Table_1). Average initial hospital charges for unhelmeted motorcyclists with brain injuries were $24,705, compared with $19,624 for helmeted motorcyclists with brain injuries.

Although some crashes will be so severe that a motorcycle helmet will not prevent brain injury or death, the proportion of injuries that could have been prevented if a motorcycle helmet had been worn by all riders was estimated for each category of head injury and death (3). These estimates assume that if unhelmeted motorcyclists wore helmets and experienced a similar distribution of outcomes as helmeted motorcyclists, then universal helmet use by all motorcyclists in Wisconsin during 1991 potentially would have prevented 60 brain injuries, 13 skull fractures with no intra- cranial injury, and eight concussions. In addition, universal helmet use potentially would have prevented 14 (18.9%) deaths. Reported by: TA Karlson, PhD, CA Quade, Center for Health Systems Research and Analysis, Univ of Wisconsin, Madison; Wisconsin Dept of Transportation. Div of Unintentional Injury Prevention, National Center for Injury Prevention and Control, CDC.

Editorial Note

Editorial Note: Motorcycle helmets are designed to protect users against injury to the brain and other head injuries. The findings in this report indicate that the use of motorcycle helmets lowers the rate of head injury. Although helmet use is approximately 99% in states with universal requirements, use is substantially less in states with laws that apply only to subgroups of the population (4). For example, in Wisconsin, where the law applies only to riders aged less than 19 years, observed helmet use is 42% for all motorcycle riders (5).

The findings in this report are subject to at least four limitations. First, incorrectly matched police reports and hospital records diminish the measure of the protective effect of helmets. Second, some motorcycle crashes in Wisconsin may not have been reported to police -- in particular, crashes occurring in areas adjacent to other states for which medical treatment may have been obtained in those states. Third, this study evaluated only hospitalized motorcycle riders; the differences in injury rates and health-care costs for unhelmeted riders compared with helmeted riders probably would have been greater if data from emergency departments and long-term -- care facilities had been available and analyzed. Skull fractures and concussions are usually associated with complete recovery, but more severe injuries to the brain can result in lifelong disability (6). Fourth, this study did not control for injuries other than head injuries. In a Washington study that controlled for severity of injuries other than head injury, motorcycle helmets were effective in limiting the occurrence of head injury, the need for and duration of mechanical ventilation, the length of intensive-care stay, and the need for rehabilitation (7). Previous studies indicate that unhelmeted riders who are injured are more likely be admitted to a hospital as an inpatient, be permanently impaired, and require ambulance service, neurosurgery, intensive care, rehabilitation, and long-term care (4).

Although the source of payment for hospitalization was not analyzed in this report, findings from previous reports indicate that public monies underwrite 25%-50% of the costs associated with motorcycle crashes (4). State-specific data on the costs for hospitalizations -- initial, long-term, and public -- for unhelmeted riders may assist state legislators in making informed decisions regarding the passage and retention of these laws.

This report illustrates how linked data can help provide information on the potential health-care costs associated with public policies intended to prevent motor-vehicle -- related injuries. Linkage of existing data systems can assist in the characterization of motorcycle and other motor-vehicle -- crash events, injury severity, and cost for non-fatal injuries. Probabilistic linkage allows large files to be linked rapidly, potentially providing information about persons involved in crashes and the severity of their injuries, the treatment they received, and charges for treatment; this information could be linked with data on the public costs of injuries associated with risk-taking behavior (e.g., drinking and driving), nonuse of safety belts and motorcycle helmets, and speeding. The Wisconsin Department of Transportation is using information from linked data about medical outcomes and the costs of crash-related injuries resulting from motorcycle and other motor-vehicle crashes to plan interventions and evaluate their impact.


  1. National Highway Traffic Safety Administration. Fatal Accident Reporting System, 1991; a review of information on fatal traffic crashes in the United States. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 1992.

  2. Wilson D. The effectiveness of motorcycle helmets in preventing fatalities. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 1989; National Highway Traffic Safety Administration Technical Report DOT no. HS-807-416.

  3. CDC. A framework for assessing the effectiveness of disease and injury prevention. MMWR 1992;41(no. RR-3).

  4. US Government Accounting Office. Motorcycle helmet laws save lives and reduce costs to society. Washington, DC: Government Accounting Office, 1990; report no. GAO/RCED-91-170, 1991.

  5. Wisconsin Office of Transportation Safety. Motorcycle helmet use in Wisconsin, 1993. Madison, Wisconsin: Wisconsin Department of Transportation, Office of Transportation Safety, 1994.

  6. Kraus JF, Rock A, Hemyari P. Brain injuries among infants, children, adolescents, and young adults. Am J Dis Child 1990;144:684-91.

  7. Offner PJ, Rivara FP, Maier RV. The impact of motorcycle helmet use. J Trauma 1992;32:636-42.

* Initial hospital charges were used as a proxy for hospital costs, which are only a portion of direct medical costs. Initial hospital charges do not include physician fees, emergency department charges, or costs after discharge for subsequent hospitalizations, long-term care, and rehabilitation.

Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Number and rate of head injury outcomes and hospital charges * for
motorcyclists and rate ratios for unhelmeted versus helmeted crash-involved
motorcycle riders + -- Wisconsin, 1991
                   Unhelmeted motorcyclists     Helmeted motorcyclists
                          (n=2015)                     (n=994)
                   -------------------------    ----------------------
                                   Hospital                   Hospital
                   No.    Rate &    charges     No.   Rate &   charges    Ratio       95% CI @
Brain injury        97     4.8    $2,396,366    17     1.7    $333,619     2.9      (1.7- 4.9)
Skull fracture
  without intra-
  cranial injury    18     0.9    $  222,707     2     0.2    $ 10,838     4.5      (1.0-19.2)
Concussion          38     1.9    $  278,786    15     1.5    $ 60,037     1.3      (0.7- 2.3)

Total              153     7.6    $2,897,859    34     3.4    $404,494     2.2      (1.6- 3.4)
* Includes charges for initial hospitalization; does not include physician fees, emergency depart-
  ment charges, or medical costs after discharge.
+ n=3184. Excludes 175 persons for whom helmet use was unknown.
& Per 100 crash-involved motorcyclists.
@ Confidence interval.

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