Booster Seats Safer for Kids Through Age 12 Years

Norra MacReady

April 21, 2017

Use of a belt-positioning booster seat is associated with a lower risk for injuries in motor vehicle crashes (MVCs) among children 8 to 12 years of age, compared with use of a seat belt alone, the authors of a new study report.

The booster seats were no more effective than seat belts at preventing fatal or incapacitating injuries, such as severe lacerations or broken bones, lead author D. Mark Anderson, PhD, and colleagues write. But there was "a strong negative association between using a booster seat and the odds of any injury from an MVC."

The study, which is one of the first to examine the benefits of booster seats in this age group, indicates that "children aged 8-12 years are considerably safer in booster seats than in seat belts," they write in an article published online April 17 in the American Journal of Preventive Medicine.

Several prominent groups, including the American Academy of Pediatrics and the National Highway Traffic Safety Administration, recommend booster seats for children up to 12 years of age. Nationwide, use of the seats by children 8 to 12 years of age increased from 5% to 10% between 2009 and 2013, the authors state. But there is little information on the effectiveness of the seats among children older than 8 years.

Dr Anderson, from the Department of Agricultural Economics and Economics, Montana State University, Bozeman, and coauthors studied data from the Washington State Department of Transportation (WSDOT) on MVCs from January 2002 through July 2015. They compared injury rates of children 8 to 12 years of age riding in booster seats with rates among similarly aged children who used seat belts alone.

The authors included only children riding in cars or light trucks. Exclusion criteria included riding in another type of vehicle, such as a motor home or school bus, and missing information on the child's age, type of restraint used, or injury severity.

The authors used the KABCO injury severity scale developed by WSDOT to determine two outcomes: the occurrence of any injury to the child related to the MVC and the occurrence of a fatal or incapacitating injury. KABCO is a five-item scale that assess MVC injuries in descending order of seriousness: K = fatal; A = incapacitating; B = nonincapacitating; C = possible injury; O = no injury.

Among 79,859 children in an MVC during the study period, 5932 (7.4%) were in a booster seat at the time of the accident, and 73,927 (92.6%) were using a seat belt. (During the study period, booster seat use in Washington by children 8 to 12 years of age went from 2% in 2002 to approximately 14% in 2015.)

Only 0.3% of the children included in the study sustained a fatal or incapacitating injury, regardless of the type of restraint used.

Among children in booster seats, 11% had any type of injury, compared with 15% of children using seat belts alone. In an unadjusted logistic regression analysis, booster seat use was associated with a 29% reduction in odds of injury compared with use of a seat belt alone: odds ratio [OR] of 0.709 (95% confidence interval [CI], 0.675 - 0.745; P < .01).

In an adjusted analysis, booster seats were associated with a 19% reduction in the risk for any injury, compared with seat belts (OR, 0.814; 95% CI, 0.749 - 0.884; P < .01). The analysis adjusted for individual-level variables (seat position, age, and sex), vehicle-level factors (vehicle age and type), and crash-level factors (number of people involved, speed limit, and time of day).

Booster seats were not associated with any change in the risk for fatal or incapacitating injuries compared with seat belts, in either the unadjusted or the adjusted analysis.

Among children 8 to 9 years of age, booster seats were associated with a 13% reduction in the risk for any injury (OR, 0.869; 95% CI, 0.818 - 0.923; P < .01), relative to seat belts. Children aged 10 to 12 years experienced a risk reduction of 33% associated with the booster seats (OR, 0.675; 95% CI, 0.505 - 0.902; P < .01). However, the authors add, these differences in risk reduction "were not statistically distinguishable" from one another.

Study limitations include a lack of information on the child's height and weight, which influences the decision on which type of child restraint system to use. Second, some of the children were in a child restraint system other than a booster seat or a seat belt and were originally coded as being in a booster seat, although removing their data from the analysis did not affect the findings.

Also, the KABCO system does not specify the type of injury sustained, and an earlier study by different investigators suggested that the risk for neck and thorax injuries is greater with booster seats than with seat belts.

Finally, the MVC data in this analysis were restricted to Washington, "and parents in Washington could be better (or worse) at positioning booster seats than parents in other states," the authors write. This might over- or underestimate the efficacy of booster seats.

Still, this analysis suggests that "children aged 8-12 years who are involved in an MVC are less likely to be injured if they are in a booster seat than if they are restrained by a seat belt alone," the authors write. Adoption of laws that encourage the use of these seats by children in this age range "could lead to fewer injuries."

The authors have disclosed no relevant financial relationships.

Am J Prev Med. Published online April 17, 201.  Abstract

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