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Effect of Seating Position and Restraint Use on Injuries to Children

in Motor Vehicle Crashes

Marc D. Berg, MD*; Lawrence Cook, MStat§; Howard M. Corneli, MD‡; Donald D. Vernon, MD*§; and J. Michael Dean, MD*§

ABSTRACT. Objective. To determine the effect of re-straint use and seating position on injuries to children in motor vehicle crashes, with stratification by area of im-pact.

Methods. Children<15 years old involved in serious automobile crashes in Utah from 1992 through 1996 were identified from statewide motor vehicle crash records. Serious crashes are defined as those resulting in occu-pant injuries with broken bones or significant bleeding or property damage exceeding $750. Probabilistic meth-ods were used to link these records with hospital records. Analysis used logistic regression controlling for age, restraint use, occupant seating position, and type of crash.

Results. We studied 5751 children and found 53% were rear seat passengers. More than 40% were unre-strained. Sitting in the rear seat offered a significant protective effect (adjusted odds ratio: 1.7; 95% confidence interval: 1.6 –2.0), and restraint use enhanced this effect (adjusted odds ratio: 2.7; 95% confidence interval: 2.4 –3.1). Mean hospital charges were significantly greater for front seat passengers.

Conclusions. Rear seat position during a motor vehi-cle crash provides a significant protective effect, restraint use furthers this effect, and usage rates of restraint de-vices are low. The rear seat protective effect is in addition to and independent of the protection offered from restraints. Pediatrics 2000;105:831– 835; seat belt usage, motor vehicle crashes, rear seat, restraints, injury, chil-dren.

ABBREVIATIONS. OR, odds ratio; CI, confidence interval.

I

njuries suffered in motor vehicle crashes are the leading cause of death in children and adoles-cents in the United States.1 The effectiveness of

seat belts and child car safety seats in preventing these injuries is well known.2,3Seating position in the

vehicle during a crash also contributes to the risk for injury, with the location of impact relative to the occupant’s seating position being an important fac-tor. In frontal impact crashes, passengers in the rear seat have a reduced risk of serious injury and mor-tality.2,4,5The combined contribution of seating

posi-tion and restraint use to injury prevenposi-tion in auto-mobile crashes has been reported.3,5–7Available data

describing the effect of restraint use and seating po-sition for children in motor vehicle crashes are in-complete; studies variously had small numbers of children, low restraint use, or were not population-based. Because of these factors, we undertook the present study.

The purpose of our study was to determine the effect of seat belt or child restraint use and seating position on injuries to children in motor vehicle crashes. Specifically, we sought to determine whether sitting in the rear seat during a serious crash provided protection to the child occupant after al-lowing for the use of an age-appropriate restraint device. Additionally, we sought to determine whether differences in outcome were observed when controlling for the confounding variable of crash type. We used probabilistic methods8 to link

state-wide motor vehicle crash and hospital databases to address both these questions. The technique of prob-abilistic linkage allowed us to create a more complete database of specific crash events and patient out-comes that we could stratify by subject age, seating position, restraint use, and crash type.

METHODS Data Source

Motor vehicle crash records for the years 1992 through 1996 were obtained from the Utah Department of Transportation. This file includes crashes reported on public roads in Utah, including all injury crashes and any crash resulting in property damage over $750. Excluded crashes were those not occurring on public road-ways and those that did not result in any occupant injuries or significant property damage. These determinations and data col-lection were performed by local law enforcement officers. The Utah crash reports include all occupants in a vehicle, including noninjured occupants.

Records include extensive information about crash circum-stances, including road, weather, and lighting conditions, vehicle damage descriptions, and driver actions. Occupant information includes age, gender, exact position within the vehicle, use of safety devices, and injury codes, as reported by the investigating police officer.

Statewide computerized hospital discharge records from 1992 through 1996 were obtained from the Office of Health Data Anal-ysis, Utah Department of Health. This database provides informa-tion about length of stay, inpatient charges, discharge diagnosis, and discharge status (outcome). The database contains all Utah hospital discharges for the 5-year period (1 077 439 discharges).

Definitions

We studied children from birth through 14 years old who were occupants in a serious automobile crash. We defined serious crashes as those resulting in a fatality, hospitalization, or a serious

From the *Divisions of Critical Care and ‡Emergency Medicine, Department of Pediatrics, and §Intermountain Injury Control Research Center, Univer-sity of Utah, Salt Lake City, Utah.

Received for publication Jun 25, 1999; accepted Dec 10, 1999.

Reprint requests to (M.D.B.) Department of Pediatrics, Division of Critical Care, Primary Children’s Medical Center, 100 N Medical Dr, Salt Lake City, UT 84113. E-mail: marc.berg@hci.utah.edu

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injury defined as injuries resulting in broken bones or significant bleeding to any of the automobile occupants. We stratified the crash victims into age groups as: young children 0 to 4 years old, school-aged children 5 to 11 years old, and older children defined as 12 to 14 years old. Vehicles were restricted to passenger cars, light trucks (including sport-utility vehicles), and vans. Children traveling in a nonpassenger area, such as a truck bed, were excluded from our analysis. As other investigators have done,2

restraint use was defined as optimal, suboptimal, or none. Opti-mal restraint included the use of a child safety seat from birth through 4 years old or use of a lap and shoulder belt for children from 5 through 14 years old. Suboptimal usage was defined as a lap belt, shoulder belt, or both in children 0 through 4 years old, or use of a lap belt or shoulder belt alone in the 5- through 14-year age groups. None means that no restraint device was used by the child.

Probabilistic Linkage

The database for analysis was constructed by linking the crash database to the hospital file using probabilistic methods. These are described in detail by Jaro.8Briefly, this technique allows linkage

of information for a single crash event among disparate databases. For example, specific details for a single crash victim contained in the crash database can be linked to hospital data for the same crash victim. The ability to link specific crash events and param-eters to hospital outcome data allows for a more complete analysis of the event in total. From this, we can make observations that would otherwise be impossible from an examination of either database individually.

Data Analysis

The data were analyzed using logistic regression with the pri-mary outcome being serious injury or death. The independent variables in our model were victim age, restraint use, type of crash, and front or rear seating position in the vehicle. Interaction covariates between seating position and crash type were also assessed. Performing multivariable logistic regression allowed us to calculate odds ratios (ORs) adjusted for all independent vari-ables in our model as listed above. Total hospital charges stratified by restraint use and seating position were secondarily evaluated.

Average hospital charges were calculated assigning a charge of $0 to passengers who were not admitted to the hospital. We defined aPvalue of⬍.05 to be statistically significant.

Probabilistic record linkage was performed using Automatch 4.1 (Matchware Technologies, Inc, Boston, MA). Multivariable logistic regression was done using SAS procedure (PROC LOGISTIC), and other statistical analyses were performed in SAS as well (SAS Institute, Inc, Cary, NC).

RESULTS Study Population

During the 5-year period from 1992 to 1996 the database included 284 550 crashes involving 464 128 vehicles and 573 772 occupants. Overall 5751 chil-dren were involved in serious crashes during the 5 years studied. Stratified by age group, this included 2016 children from birth through 4 years old, 2231 children from 5 through 11 years old, and 1504 chil-dren from 12 through 14 years old. There were 2383 children seriously injured, 134 children hospitalized, and 53 killed.

Seating Position and Restraint Usage

As might be expected, a larger percentage of older children sat in the front seat. A total of 2441 children were in the front seat and 3310 were in the rear seat at the time of the crash. We found 743 (37%) young children, 947 (42%) school-aged children, and 751 (50%) older children were riding in the front seat at the time of the crash. Restraint usage varied by age group and seating location in the vehicle (Fig 1). Of all children, 38% (2168 of 5751) were optimally re-strained. Moreover, 27% of children 0 to 4 years old, 44% of children 5 to 11 years old, and 52% of children

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12 to 14 years old were unrestrained in the crash. Suboptimal restraint use was noted in 34% of chil-dren birth to 4 years old versus 13% of chilchil-dren 12 to 14 years old (P ⬍ .01). The percentage of children optimally, suboptimally, or not restrained did not vary whether they were in the front or back seat (Table 1).

Injury Frequency

Controlling for age and restraint use, a child was 1.7 times more likely to suffer a serious injury or fatality when sitting in the front seat versus the rear seat during a crash. When age and seating position were controlled for, the benefit of restraints was clearly seen (Table 2). When restraints were opti-mally used, occupants were 2.7 times more likely to endure the crash without serious injury or fatality than unrestrained children, regardless of seating po-sition. There was no significant difference between optimal and suboptimal restraint use in preventing serious injury or death (adjusted OR: 1.2;P⫽ .94).

There were 53 deaths during this 4-year period yielding a fatality rate of .9% for children involved in serious crashes. Sixty percent of deaths occurred to front seat passengers versus 40% to those in the rear seat at the time of the crash. No form of restraint device was used in 70% of fatally injured passengers, 25% were optimally restrained, and 5% were subop-timally restrained.

Rear Seat Protection by Crash Type

We examined the odds of suffering serious or fatal injury, in relation to seating position, regardless of restraint use. Because the forces to which an occu-pant was exposed vary greatly depending on where they were sitting and where the primary impact oc-curred, we controlled for crash type. Rear seat pas-sengers, compared with those in the front seat, were significantly less likely to be seriously injured or killed in frontal impact crashes (adjusted OR for injury: .73; 95% confidence interval [CI]: .60-.90). Rear seat occupants were also better protected against serious injury or death than those in the front seat during nonfrontal impact crashes (adjusted OR for injury: .57; 95% CI: .51-.64).

Hospital Admission Rates and Charges

Only 2.3% of crash victims required hospitaliza-tion (134 of 5751). By seating locahospitaliza-tion, 2.6% (64 of 2441) of front seat passengers and 2.1% (70 of 3310) of rear seat passengers were admitted to the hospital. This difference was not significant (P⫽.2). Regard-less of seating location, 1.2% (25 of 2168) of restrained and 3.3% (75 of 2301) of unrestrained victims re-quired hospitalization (P ⬍ .001), underscoring the importance of restraints in preventing injury and

decreasing the need for hospitalization. The unin-jured occupant hospital charge was $0; the mean inpatient hospital charge for all front seat passengers was $284.18. This was significantly greater than that for rear seat passengers, which was $194.74 (P⫽.02). Unrestrained front seat passengers requiring admis-sion incurred the highest hospital charges, averaging $11 190 (⫾$6930, 2 standard deviations), with a range from $540 to $139 470. Conversely, optimally re-strained rear seat occupants incurred the lowest mean hospital charge averaging $6950 (⫾$3380, 2 standard deviations), 62% lower than those unre-strained in the front seat.

DISCUSSION

This study confirms that sitting in the rear seat during a motor vehicle crash offers a significant pro-tective effect, restraint use enhances this effect, and usage rates of restraint devices are too low. The protective effect of the rear seat in a crash is in addition to the protection offered by restraints. Na-tionwide, 68% of automobile passengers used seat-belts in 1996, and a federal directive in January 1997 established a goal of 85% seatbelt usage with a goal of reducing child occupant fatalities 15% by the year 2000.9 Nevertheless, our data show that many

chil-dren remain unrestrained in cars at the time of a crash, significantly increasing their risk for serious injury or death.

Huelke and Compton4reported the effect of seat

belts on injury severity to front and rear seat passen-gers in the same frontal impact crash.4 They found

that for adult victims of frontal impact crashes the rear seat was a safer location than the front seat. This observation also applied to rear-seated children 5 to 14 years old when they were in the same crash event. Only 8% of unrestrained rear-seated child passen-gers suffered a more severe injury, defined as one with a higher maximum abbreviated injury scale score, than an unbelted adult front seat passenger. When restraints were used, only 5% of children in the rear seat had a more severe injury than their front seat adult counterpart. Our data confirm that being in the rear seat during a crash is protective, with or without the use of restraints.

To expand on this observation, we examined the outcomes of rear seat passengers stratified by crash type. Because of the forces involved, frontal impact crashes are more injurious overall, and front seat passengers are 1.3 times more likely to be seriously injured or killed than those in the rear seat. We and others2,7 have observed that rear seat pediatric

pas-sengers have decreased risks of morbidity and mor-TABLE 1. Restraint Use by Seating Location

n(Percent) None

Optimal Suboptimal

Front 962 (39) 380 (16) 1099 (45) Back 1206 (37) 902 (27) 1202 (36)

TABLE 2. ORs of Serious Injury or Death

Variable OR 95% CI

Restraint usage (vs optimal restraint)

Suboptimal restraint 1.2 1.0–1.6

No restraint 2.7 2.4–3.1

Seating position (vs back seat)

Front 1.7 1.6–2.0

Age (vs 0–4 y)

5–11 y 1.2 1.1–1.5

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tality when involved in serious automobile crashes. In our analysis, the protective effect of the rear seat persists, even in the more dangerous frontal impact crashes (adjusted OR: .73; 95%CI: .6-.9). An even greater protective effect is observed in rear seat pas-sengers who are in nonfrontal impact crashes (ad-justed OR: .57; 95% CI: .51-.64).

As children age, fewer are restrained when riding in an automobile. Twice as many children 12 to 14 years old are unbelted than are younger children 0 to 4 years old (Fig 1). This may be because older chil-dren are responsible for securing themselves without direct parental supervision or involvement. Further-more, adolescents may view wearing a seat belt as uncool and may shun the seat belt for approval from their peers. Given their level of development, younger children must have an adult restrain them correctly and thus may be more likely to be re-strained.

Suboptimal restraint usage decreases significantly as children age. Children 0 to 4 years old are 2.5 times more likely to be incorrectly restrained (which in this age group includes wearing a seat belt) at the time of a crash than children 12 to 14 years old. For young children, seat belt use carries risks because these restraint systems are engineered for the larger (⬎80-lb) body.9 Blunt abdominal trauma, a specific

pattern of which known as the seat belt syndrome, is observed in small children held by seat belt systems designed for adults.10Despite their potential for

cre-ating specific patterns of injury in the pediatric pa-tient, seat belts are still proven to reduce mortality, injury severity, length of hospital stay, and chance of permanent impairment.11Their correct use offers the

greatest benefit.

The calculated mean hospital charges may seem low to the clinician. However, these reported charges are mean values of all crash victims including those not admitted to the hospital. We computed the mean values using a charge of $0 for nonhospitalized sub-jects to account for the large number of people who benefited from a restraint device or seating position and did not require hospitalization. This further il-lustrates the primary importance of restraint use as a preventive measure, reducing serious injury or mor-tality, and health care costs. When this selection bias is not accounted for, and mean charges are calculated based only on those patients admitted to the hospi-tal, we could not detect any difference in hospital charges to those in the front versus rear seat, with or without restraints. This demonstrates selection bias in that those suffering injuries severe enough to re-quire hospitalization, regardless of the circum-stances, may incur similar charges. When examined in total, if all children were in the rear seat, there would have been 306 fewer injuries during this pe-riod. When multiplied by the average hospital charge per injured child, this equals a potential sav-ings of $236 800 to the health care system in Utah alone.

Despite the known protective effect of rear seat position for children, few public health interventions have been made in this area. A recent exhaustive review identified studies evaluating interventions

promoting pediatric rear seat use,123 of which

dem-onstrated a significant increase in rear seat use after a public health intervention. The intervention was an educational effort in 1 case, and a legislative initia-tive in 2 cases. As the evidence for improved safety and better crash outcomes to rear-seated children becomes more conclusive, educational or legislative efforts to increase rear seat use will be increasingly important. Ongoing evaluation of the efficacy of these advocacy efforts will be crucial.

The limitations of this study are those that are inherent to research of this nature, primarily inaccu-racy in crash reporting and data entry.13 Crashes in

which no law enforcement official was notified, those occurring on private property (not on public roads), and those not meeting our previously stated inclu-sion criteria are not included in the database, and thus are not available for our analysis. Finally, use or nonuse of restraints is self-reported by the crash victims who may overreport their use. Selective overreporting is known to occur more among less severely injured passengers. This inflates the appar-ent effectiveness of seat belts.14Given that our study

population is children involved in crashes with a serious injury or fatality, these limitations should bias our results minimally.

CONCLUSION

In summary, sitting in the rear seat and using an age-appropriate restraint device significantly and in-dependently decrease the risk of serious injury or death to children involved in serious automobile crashes. Optimal restraint usage rates were low in this study,⬍40% across all ages studied. Moreover, one third of the youngest children, 0 to 4 years old, were wearing an adult seat belt at the time of the crash when the appropriate restraint would have been a child safety seat. Nonuse or suboptimal re-straint use places our children at unnecessarily high risk for serious injury or death. This should be con-sidered when counseling patients and parents on car safety.

ACKNOWLEDGMENTS

This research was supported by Cooperative Agreement Grant DTNH22-92-Y-57329 from the National Highway Traffic Safety Administration, United States Department of Transportation; and Cooperative Agreement Grant MCH-494003-03-0 from the Mater-nal and Child Bureau, Health Resources and Services Administra-tion, Public Health Service, United States Department of Health and Human Services.

We thank the Utah Department of Transportation for providing research access to the crash files used in this study and the Office of Health Data Analysis, Utah Department of Health, for provid-ing access to the inpatient hospital discharge database.

REFERENCES

1. Centers for Disease Control and Prevention. Childhood injuries in the United States.Am J Dis Child. 1990;144:627– 646

2. Johnston C, Rivara F, Soderberg R. Children in car crashes: analysis of data for injury and use of restraints.Pediatrics. 1994;93:960 –965 3. Bodiwala G, Thomas P, Otubshin A. Protective effect of rear-seat

re-straints during car collisions.Lancet. 1989;1:369 –371

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5. Agran P, Winn D, Dunkle D. Injuries among 4- to 9-year-old restrained motor vehicle occupants by seat location and crash impact site.Am J Dis Child. 1989;143:1317–1321

6. Periodou E, Skalkidou A, Lescohier I, Trichopoulos D. Car restraints and seating position for prevention of motor vehicle injuries in Greece.

Arch Dis Child. 1998;78:335–339

7. Williams A, Zador P. Injuries to children in automobiles in relation to seating location and restraint use.Accid Anal Prev. 1977;9:69 –76 8. Jaro M. Probabilistic linkage of large public health data files.Stat Med.

1995;14:491– 498

9. National Highway Transportation Safety Administration. National Highway Transportation Safety Administration Data. Washington, DC: Na-tional Highway Transportation Safety Administration; 1999

10. Hoffman M, Spence L, Wesson D, Armstrong P, Williams J, Filler R. The pediatric passenger: trends in seatbelt use and injury patterns.J Trauma. 1987;27:974 –976

11. Osberg J, DiScala C. Morbidity among pediatric motor vehicle victims: the effectiveness of seat belts.Am J Prev Med. 1992;82:422– 425 12. Segui-Gomez M. Evaluating interventions that promote the use of rear

seats for children.Am J Prev Med. 1998;16:23–29

13. Agran P, Castillo D, Winn D. Limitations of data compiled from police reports on pediatric pedestrian and bicycle motor vehicle events.Accid Anal Prev. 1992;22:361–370

14. Dean J, Reading J, Nechodom P. Overreporting and measured effective-ness of seat belts in motor vehicle crashes in Utah.Transportation Rev Board. 1995;1485:186 –191

THE EXPENSIVE WAR AGAINST DEATH AND AGING

Trying to cope with the inevitably expanding health needs of the elderly by means of ever more expensive technologies with marginal health benefits to the population as a whole makes little economic sense. Conversely, to think that we can manage growing costs through cost reductions at the end of life and greater application of evidence-based medicine is far too optimistic.

My pessimism regarding the possibility of achieving a technical correction through outcome assessment studies runs counter to prevailing sentiments within US medicine. One reason for this pessimism is that the pharmaceutical and medical manufacturing industries are endlessly adept at developing new technologies, hardly any of them curative and most of them expensive. US physicians, with the eager support of their patients and sometimes the reluctant assent of HMOs, are ready to adopt these technologies. War has been declared against death and its historical ally, aging.

Callahan D. Aging, death and population health.JAMA.1999;282:2077

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DOI: 10.1542/peds.105.4.831

2000;105;831

Pediatrics

Michael Dean

Marc D. Berg, Lawrence Cook, Howard M. Corneli, Donald D. Vernon and J.

Vehicle Crashes

Effect of Seating Position and Restraint Use on Injuries to Children in Motor

Services

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DOI: 10.1542/peds.105.4.831

2000;105;831

Pediatrics

Michael Dean

Marc D. Berg, Lawrence Cook, Howard M. Corneli, Donald D. Vernon and J.

Vehicle Crashes

Effect of Seating Position and Restraint Use on Injuries to Children in Motor

http://pediatrics.aappublications.org/content/105/4/831

located on the World Wide Web at:

The online version of this article, along with updated information and services, is

by the American Academy of Pediatrics. All rights reserved. Print ISSN: 1073-0397.

Figure

Fig 1. Restraint usage by age. Open bars represent from birth to 4 years old, gray bars represent 5 to 11 years old, and solid bars represent12 to 14 years old.
TABLE 2.ORs of Serious Injury or Death

References

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