OBJECTIVE. To shed light on the extent to which childhood obesity affects the types of appropriate child safety seats for young children, by providing an estimate of the number of US children whose weight renders them unable to use safely the majority of child safety seat types currently available.
METHODS. The types of appropriate child safety seats were assessed by using National Highway Traffic Safety Administration 2005 Child Safety Seat Ease of Use Ratings. Estimates of the numbers of children weighing above the maximal weight for those child safety seats were calculated by using the tabulations of growth curves based on National Health and Nutrition Examination Survey 1999 to 2000 data that were assembled by the National Center for Health Statistics and the US Census for the year 2000.
RESULTS. A total of 283305 children 1 to 6 years of age would have a difficult (if not impossible) time finding a safe child safety seat because of their age and weight. The vast majority of these children are 3 years of age and weigh >40 lb (182661 children). For these children, there are currently only 4 child safety seat types available, each of which costs between $240 and $270.
CONCLUSIONS. This study determined that there is limited availability of child safety seat types for the ever-increasing number of obese young children. There are substantial numbers of children who weigh more than the upper weight limit for most currently available child safety seats. While we await reductions in the childhood obesity epidemic, options for maximizing the protection of obese children in automobiles must be identified.
CHILDHOOD OBESITY IS a critical public health threat for the 21st century.1–4 Childhood obesity affects children in all 50 states, including boys and girls and younger children and adolescents of all socioeconomic groups and all ethnic backgrounds. Specific ethnic groups, ie, black, Hispanic, and American Indian groups, are affected disproportionately. Childhood obesity is defined as an age- and gender-specific BMI of ≥95th percentile on the 2000 Centers for Disease Control and Prevention (CDC) BMI charts.5 For most children, these values are known to indicate elevated body fat and to reflect the comorbidities associated with excessive body fatness.5 Estimates of childhood obesity are as high as 10% for children 2 to 5 years of age in the United States.6 In the past 3 decades, the rates of childhood obesity have doubled for children 2 to 5 years of age and for adolescents 12 to 19 years of age and have tripled for children 6 to 11 years of age.6 The weight levels of children, as a population, are taking a “harmful upward trajectory,” according to the Institute of Medicine.5 A 1998 survey of children participating in the Supplemental Nutrition Program for Women, Infants, and Children found that 13% of enrolled children were overweight.7 Weight-for-length values of >95th percentile are used by the CDC and the Special Supplemental Nutrition Program for Women, Infants, and Children to define overweight for children in this age group. Recent analyses indicate that the extent of overweight (ie, the degree of overweight among those who are overweight) in this subpopulation has increased even more rapidly than the prevalence of overweight among all US children and adolescents.8
“Defining overweight at or above the 95th percentile of the growth curves implies that, if the distribution of weight-for-height or BMI in the current population matches the distribution in the reference population, then we will observe an overweight prevalence of 6 percent. Overweight prevalence in excess of 6 percent signals a shift in the population distribution of weight-for-height.”9 This prevalence (that is, 10% and as high as 13% for boys and girls participating in the Supplemental Nutrition Program for Women, Infants, and Children) indicates a shift in population distribution of weight-for-height values, rendering more children obese.
Obesity is not merely about personal aesthetics or preference but is strongly associated with health indicators.6,10 Obesity is linked to many chronic disease risks, including cardiovascular disease11 and type 2 diabetes mellitus.12 To our knowledge, however, no one has yet reported that the obesity epidemic has implications that extend beyond well-being, health, and aesthetics, into the realm of childhood safety. There may be limited availability of child safety seat types for the ever-increasing number of obese young children. This article sheds light on the extent to which this situation poses a real danger and a challenge to obese children and their families.
Child Passenger Safety and Child Safety Seats
Nationally, motor vehicle crashes pose the single greatest risk to children, accounting for 23% of injury deaths among infants and 30% among preschool-aged children.13 Year after year, injuries resulting from motor vehicle crashes continue to be the leading cause of death for children in the United States.14 More than 1.5 million children are in motor vehicle crashes each year.15 Like childhood obesity, injuries affect disproportionately the poor and certain minority populations.16 Child safety seats have been recommended as best practice for protecting children traveling in cars17–19 and have been demonstrated to be effective protection in motor vehicle crashes, reducing the risk of fatal injury by 71% for infants (rear-facing infant safety seats) and by 54% for toddlers (forward-facing child safety seats).20 Rear-facing infant safety seats or convertible seats used in the rear-facing position are generally appropriate for infants from birth to at least 1 year of age, weighing up to 20 lb.21 Forward-facing child safety seats are typically appropriate for children 1 to 4 years of age who weigh ≥20 to ∼40 lb. Booster seats, which typically can accommodate children weighing up to 80 or 100 lb, are recommended once children weigh 40 lb and/or are 4 years of age, followed by adult seat belts once children are 4 feet 9 inches (57 inches) tall.21
“Children who are under about 4 years old or are very active may not stay put without a 5-point harness system that holds them in place. Booster seats do not work well for these children because vehicle shoulder belts do not prevent them from leaning forward or placing the shoulder belt behind the back or under the arm.”22 Therefore, developmental considerations result in recommendations that preclude children <4 years of age from using booster seats without a harness system.22 The importance of age and weight appropriateness of child safety seats (for children weighing <80 lb) was highlighted by a group of child passenger safety professionals as a critical potential misuse issue that “could reasonably be expected to raise the risk of injury to a child in the event of a crash.”23
Obese Children and Child Safety Seats
The effect of the childhood obesity epidemic has become evident at our own Children’s Safety Center (CSC). The CSC is a hospital-based safety resource center that has had documented success in meeting the unique barriers to injury prevention among low-income, urban families.24,25 The CSC has both an infant safety seat loaner program and a low-cost sales program for convertible and booster seats. Nationally certified child safety seat technicians in our CSC have observed a number of obese children who weigh more than the upper weight limit for many available child safety seats, and they have reported anecdotally their difficulties in finding appropriate child safety seats for these children. These experiences led us to examine the population-level implications of the childhood obesity epidemic on child occupant protection. Specifically, the purpose of this study was to estimate the number of children in relevant age groups in the United States whose weight exceeds the limit for most types of available child safety seats.
Determining Types of Available Child Safety Seats
The National Highway Traffic Safety Administration (NHTSA) 2005 Child Safety Seat Ease of Use Ratings26 were used to determine the types of available child safety seats on the market. The NHTSA 2005 ratings provide information on 92 child safety seats, including manufacturer, model name, model number, date of manufacture, harness type, and weight/height range. With all of the multiple models of convertible and combination seats, there are 144 ratings in total. A child safety seat type was determined to be available to accommodate a child if that child safety seat met weight and age or developmental recommendations simultaneously. Before 1 year of age, typically infant safety seats accommodate children up to 20 lb. Most currently available child safety seats with 5-point harness systems (for children 1–3 years of age) accommodate children up to 40 lb. Most belt-positioning booster seats (for children ≥4 years of age) accommodate children weighing up to 80 lb. For the purposes of this study, children were identified as having limited child safety seat options if they were <1 year of age and weighed >35 lb, were 1 to 3 years of age and weighed >41 lb, or were 4 to 6 years of age and weighed >81 lb. Children who weighed more than the maximal weight specified by the particular child safety seat manufacturer would be considered ineligible to use that child safety seat.
Determining Numbers of Children Affected
The number of children (population affected) whose child safety seat usage was limited by their weight was determined by using tabulations of growth curves based on 1999 to 2000 National Health and Nutrition Examination Survey (NHANES) data, as assembled by the National Center for Health Statistics (NCHS), and 2000 US Census data.27 The growth curves are available according to gender and age (in months) for 2 genders × 84 months, yielding 168 separate cells for children in the 1999 to 2000 NHANES results. The NCHS uses a flexible functional form known as the Box-Cox transformation to fit growth curves to the raw data on child age and weight. The Box-Cox transformation is Box-Cox W = (Wλ − 1)/λ. (λ is the Box-Cox parameter that will normalize Z.) With the Box-Cox transformation, the distribution of weights for children of any given age is approximately normal. The NCHS has tabulated parameters for the median, the coefficient of variation, and the Box-Cox transformation parameters for each gender according to age (in months).27 Given these estimates and the assumption that the Box-Cox-transformed data are normal, we could use the cumulative normal distribution to determine the probability that a child’s weight would be above any defined child safety seat weight limit. This was implemented by using the retransformation formula supplied by the CDC and is reproduced here to calculate z scores for each of the age/gender cells at the exact weight cutoff values of interest, ie, z = [(X/M)λ − 1]/λS, where, for each age/gender cell, X is the weight threshold of interest, M is the median weight, λ is the Box-Cox parameter, and S is the coefficient of variation.
Table 1 presents the number of types of child safety seats available according to age, weight, and cost. There are 4 child safety seats from the NHTSA 2005 Child Safety Seat Ease of Use Ratings26 that can accommodate a 3-year-old child weighing >41 lb. The average cost for each of these 4 child safety seats ranges from $240 to $270 (manufacturer’s suggested retail prices). Table 2 presents the population estimates according to child age, weight, and average z score for each category of age and weight.
It was determined that there were 283305 children whose age/weight combinations placed them at risk for difficulty in obtaining an appropriate child safety seat. Children (male and female) 3 years of age who weighed >40 lb represented the age/weight group with the largest number of children affected (94030 boys and 88631 girls). A total of 1.04% of all children from birth to 6 years of age (83 months) were affected. For 182661 children 3 years of age, there are only 4 available child safety seat types that can accommodate the weight range and developmental recommendations, all of which cost more than $240 each.
A significant short-term effect of childhood obesity is that many children may not have access to an approved child safety seat because there are no seats appropriate for their age and weight and, for some age/weight combinations, the few available seats are priced out of many families’ reach. According to our estimates, 8683 children 2 years of age, 182661 children 3 years of age, and 91927 children 4 to 6 years of age may have a difficult (if not impossible) time finding an appropriate child safety seat for their age and weight. Obesity is generally considered a health problem with long-term consequences; however, there is an immediate need for child safety seats that have been designed, tested, and approved for use at higher weights. Debate regarding what to do to reduce and to prevent childhood obesity and how to do it is just beginning. We do know, however, that childhood obesity is increasing, and we can expect even more children to face the prospect of limited or no child safety seats available to protect them. The rates of childhood obesity have doubled and even tripled for some age groups, and child passenger safety professionals, health care providers, and parents must be prepared for similar trends in the next decade. We cannot wait for the prevention or reduction of childhood obesity to eliminate this problem.
Limited availability of child safety seat types for obese children is more worrisome for low-income families, who are (1) more at risk for injuries and more likely to die as a result of injuries,16,28,29 (2) less likely to implement safety practices,30 and (3) more at risk for obesity.7 Fewer financial resources for low-income families add to the burden of finding affordable and appropriate child safety seats for obese children. The costs of the child safety seats that would accommodate children in the age/weight combinations identified in this study range from as low as $14 to as high as $270. The costs of the only 4 child safety seats appropriate for 3-year-old children weighing >41 lb (the group with the largest number of children affected) begin at $240. Some community programs (including our own) provide free or reduced-cost child safety seats; the extent to which these programs are able to provide seats appropriate for these unique age/weight combinations is unknown.
Because of the limited availability of child safety seats for obese children and their related cost, parents of obese children may find themselves in violation of child occupant protection laws. All 50 states and the District of Columbia have child occupant protection laws. At least 33 states and the District of Columbia have booster seat laws currently in place.31 These laws vary widely in their age requirements, exemptions, enforcement procedures, and penalties.31 However, most child occupant protection laws mandate that children under certain ages, regardless of weight, be restrained properly in appropriate child safety seats. The enforcement of these laws varies, although many states impose a fine for a child restraint violation. The model legislation offered by the National SAFE KIDS Campaign does not specify weight; instead, the legislation uses the term “size” to address the weight/height combination.32 How should parents be instructed? What should child safety seat technicians do when child safety seats are neither available nor affordable? These questions require additional empirical evidence regarding the crashworthiness of seats used by children who exceed the recommended weight limits and the effect of using adult seat belts when a child is too heavy for any safety seat but is not developmentally ready for an adult seat belt.
We have likely underestimated the number of children in these relevant age and weight groups. The CDC growth charts remain unchanged from the initial release on May 30, 2000; however, given the trend in childhood obesity, it is likely that the estimates will be higher when updated NHANES data are available.
We used the best available information on child safety seat availability and cost. However, child safety seat manufacturers and retailers are always making changes in the products and their costs, which could affect future estimates. We hope that the results of this study can be used to influence future products brought to market. Our findings should also be useful to decision-makers who determine acceptable safety standards and testing requirements.
As the number of obese children in the United States increases, it is essential to develop child safety seats that can protect children of all sizes and shapes. The rates of childhood obesity have more than doubled for certain age groups in the past decade, and we can expect these increases to continue. The group identified in this study as having the most affected children was the 3-year-old group; affected children represented 4.76% of the total 3-year-old population. Therefore, the group of greatest concern is the 3-year-old group, because of the percentage affected (4.76%), the limited number of child safety seats available (4 total), and cost of those child safety seats (more than $240).
This research was supported by the Johns Hopkins Bloomberg School of Public Health, Center for Injury Research and Policy (CDC grant R49CCR302486).
- Accepted August 29, 2005.
- Address correspondence to Lara B. Trifiletti, PhD, MA, Columbus Children’s Research Institute, 700 Children’s Dr, Columbus, OH 43205. E-mail:
Dr Trifiletti was employed by Johns Hopkins Bloomberg School of Public Health at the time of this study and is now employed by the Children’s Research Institute, Ohio State University.
The authors have indicated they have no financial relationships relevant to this article to disclose.
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- Copyright © 2006 by the American Academy of Pediatrics