- Email: [email protected]
Prevalence of Overweight in Children with Developmental Disorders in the Continuous National Health and Nutrition Examination Survey (NHANES) 1999-2002
PREVALENCE OF OVERWEIGHT IN CHILDREN WITH DEVELOPMENTAL DISORDERS IN THE CONTINUOUS NATIONAL HEALTH AND NUTRITION EXAMINATION SURVEY (NHANES) 1999-2002 LINDA G. BANDINI, PHD, RD, CAROL CURTIN, MSW, CHARLES HAMAD, PHD, DAVID J. TYBOR, MS, MPH, AND AVIVA MUST, PHD
Objective To estimate the prevalence of overweight in children identified with developmental disorders on the basis of nationally representative survey data. Study design We estimated the prevalence of overweight in children with developmental disorders on the basis of a recent large nationally representative survey. The continuous National Health and Nutrition Examination Survey (NHANES) 1999-2002 included 4 questions to identify children with developmental disorders. Height and weight were used to calculate body mass index (BMI). BMI percentiles were estimated relative to the age- and sex-specific Centers for Disease Control and Prevention growth reference. The 85th percentile BMI defined at-risk-for-overweight and the 95th percentile BMI defined overweight. Results We found a higher prevalence of at-risk-for overweight and overweight among children with limitations in physical activity and a higher prevalence of overweight in girls with learning disabilities, compared with children without these conditions, after adjustment for age and race-ethnicity. Conclusion To the extent that children with developmental disorders are included in large representative surveys, the data suggest that children with developmental disorders have a risk for overweight that is at least as great as that of typically developing children. (J Pediatr 2005;146:738-43) he prevalence of overweight among US children has been escalating.1 Little has been done to determine the prevalence of and risk factors for obesity in children with developmental disorders, in this case, children who have physical limitations, learning disabilities, attention disorders, and those who receive special education services. The importance of this inquiry was underscored by a conference convened in 2001 by the Surgeon General that addressed the health needs of individuals with mental retardation (MR) and developmental disabilities.2 The conference report called for research and clinical intervention to address the specific health needs of persons with MR and to develop health promotion programs that seek to improve their overall health and wellness. In this study, we used data derived from a recent nationally representative survey, the National Health and Nutrition Examination Survey (NHANES) 1999-2002, to estimate From University of Massachusetts Medical School, Eunice Kennedy the prevalence of overweight in children with developmental disorders. Measured heights Shriver Center, Waltham, Massachu3 and weights from the NHANES 1999-2002 survey were used to estimate the prevalence setts; Boston University, Boston, Massachusetts; Friedman School of of at-risk for overweight or overweight in children with developmental disorders. We Nutrition Science and Policy, Tufts hypothesized that children with developmental disorders would be at higher risk for University, Boston, Massachusetts; and Department of Public Health overweight than their typically developing peers. The complex medical, physical, and and Family Medicine, Tufts University psychosocial difficulties that these children encounter may put them at higher risk for School of Medicine, Boston, Massaobesity. For example, dietary factors such as the use of food as a behavioral reinforcer or chusetts. Submitted for publication Aug 9, mealtime behaviors that influence food choices or parental meal preparation may lead to an 2004; last revision received Nov 24, energy imbalance. Lack of participation in physical activity opportunities because of a lack 2004; accepted Jan 25, 2005. of inclusion in team sports, poor coordination, and/or social isolation may contribute to Reprint requests: Linda G. Bandini, PhD, RD, University of Massachusetts positive energy balance and, in time, to increased weight gain. Furthermore, because of the Medical School, Eunice Kennedy numerous physiological, social, and educational demands and stresses associated with Shriver Center, 200 Trapelo Rd, raising a child with a developmental disorder, weight control may not be a priority for the Waltham, MA 02452. E-mail: Linda.
T
BMI CDC LD
738
Body mass index Centers for Disease Control and Prevention Learning disability
MR NHANES
Mental retardation National Health and Nutrition Examination Survey
[email protected]. 0022-3476/$ - see front matter Copyright ª 2005 Elsevier Inc. All rights reserved. 10.1016/j.jpeds.2005.01.049
families of these children. In this report, we estimated the prevalence of overweight in children with physical limitations, children receiving special education or early intervention services, and children with attention deficit disorder or learning disabilities. We also explored whether the prevalence of overweight varied by age and sex.
Disease Control and Prevention (CDC) growth reference standards.4 We adopted CDC terminology to define at-riskfor-overweight and overweight. At-risk-for-overweight is defined as a BMI >85th percentile and overweight is defined as a BMI >95th percentile.5
Statistical Analyses
METHODS NHANES is a series of national examination studies conducted in the United States since 1970. After the NHANES III 1988-1994 survey, the periodic examination surveys became a ‘‘continuous’’ survey. Since 1999, data have been collected every 2 years from a representative sample of the US population; approximately 7000 subjects from different locations are sampled. In the basic protocol for all these surveys, randomly selected subjects are first interviewed in their homes, and information on demographics, socioeconomic status, diet, and health-related questions are obtained. In a mobile examination center, body weight and height are measured with a standard protocol. Weight is measured to 2 decimal places with an electronic-load cell scale in kilograms; height is measured with a fixed stadiometer. Children who are unable to stand are not weighed and therefore are not included in this analysis. Unfortunately, the number of children not weighed for this reason is not available from the public use dataset. Survey items from the 1999-2002 NHANES identified children with developmental disorders. Because of the dearth of this information in comprehensive nationally representative surveys, we selected questions that would suggest that the child had a developmental disorder. We limited our analyses to children aged 6.0 to 17.9 years to reflect the school-age years of typically developing children. Although many children who receive special education services remain in high school until the age of 22 years, they were not included in our analysis because the data on reference children would not be comparable. The NHANES 1999-2002 combined survey has an examination sample size of 19,759. Details of the sampling design and survey elements are available.3 In the continuing survey, we selected 4 questions that identified children with developmental disorders as follows: (1) children with physical limitations; (2) children receiving special education or early intervention services; (3) children with attention deficit disorder; and (4) children with learning disabilities. (Appendix; available online at http://www.us.elsevierhealth. com/jpeds). Items that identified children receiving special education services and children with a learning disability were asked only of children aged 6 to 14.9 years.
Criteria for Overweight Body mass index (BMI) was calculated from measures of height and weight (kg/m2) and used to identify overweight. To provide a measure of relative weight, a BMI z-score was calculated for each BMI measure, with the reference to ageand sex-specific parameters provided by the Centers for Prevalence Of Overweight In Children With Developmental Disorders In The Continuous National Health And Nutrition Examination Survey (NHANES) 1999-2002
For each survey, the analytic dataset consisted of all children with a measured height and weight whose parents responded to the identified survey items. Prevalence of at-riskfor-overweight and overweight were estimated for the entire population and for individuals with a positive response to the questions about developmental disorders. We tested the statistical significance of the differences in prevalence by group using chi-square tests. Multivariate logistic regression analysis was undertaken to estimate the relative risk of at-risk-for overweight and overweight (and their 95% confidence limits) for children with developmental disorders compared to children not identified as having developmental disorders, after controlling for age, sex, and race-ethnicity. Racial-ethnic categories were constructed for non-Hispanic white, non-Hispanic black, Hispanic, and other. Interactions were tested between each condition and sex; when the interaction term was statistically significant, results were stratified by sex. Data were analyzed using SAS software (version 8.02; SAS Institute, Cary, NC) and SUDAAN software (version 8.0, Research Triangle Institute, Cary, NC). We included 4-year sample weights to adjust for unequal selection probabilities and over-sampling in the complex samples. In the combined NHANES 1999-2002, masked variance units as pseudo-primary sampling units were used, as recommended.6 When the P value was <.05, results were deemed to be statistically significant.
RESULTS In the NHANES 1999-2002 dataset, 4 questions identified 1128 children with developmental disorders. Specifically, items identified children with physical limitations, attention deficit disorder, learning disability, and those receiving special education or early intervention services. Of the 1128 children, 654 (57.9%) had 1 of these conditions, 327 (28.9%) had 2 of these conditions, 133 (11.8%) had 3 of these conditions, and 14 (1.2%) had all 4 of these conditions. The most frequent coexisting diagnoses were that 40.4% and 31.8% of children with learning disabilities and attention deficit disorder, respectively, also received special education services. The percentage of children aged 6 to 17 years with health problems that limit their ability to walk play or run was 4.1% (SE, 0.38). Children with these physical activity limitations were significantly more likely to be at-risk-foroverweight than those without physical activity limitations (50.9% versus 30.6%, P <.001, Table I). These children were also more likely to be overweight (29.7% versus 15.7%, P <.01). In sex-specific analyses, girls with physical limitations had a significantly higher prevalence of at-risk-for-overweight 739
Table I. Prevalence of at-risk-for-overweight (85th percentile) and overweight (95th percentile) by sex, age and condition (%): NHANES 1999-2002 Limitations in Crawling, Walking, Running, and Playing At-Risk-For- Overweight (%) Sex
Overweight (%)
Age (y)
With limitations
No limitations
With limitations
No limitations
All All 6-8 9-11 12-14 15-17 All 6-8 9-11 12-14 15-17
50.9 52.5 85.9 52.7 50.3 32.2 49.2 44.9 63.8 62.8 24.7
30.6* 31.7* 31.7 31.7 30.6 32.9 29.5* 26.9 32.3* 32.1* 26.8
29.7 31.3 56.3 24.0 27.3 24.7 28.1 38.2 38.8 24.5 22.0
15.7* 16.9 16.3 16.6 16.1 18.9 14.5* 12.5 16.0* 17.2 12.5
Both Male
Female
*significantly different prevalence of at-risk for overweight or overweight between children with and without the condition, by chi-square, p<0.05.
Table II. Prevalence of at-risk-for-overweight (85th percentile) and overweight (95th percentile) by sex, age and condition (%): NHANES 1999-2002 Enrollment in Special Education Services or Early Intervention (EI) At-Risk-For- Overweight (%) Sex Both Male
Female
Overweight (%)
Age (y)
Enrolled in Special Education/EI
Not Enrolled in Special Education/EI
Enrolled in Special Education/EI
Not Enrolled in Special Education/EI
All All 6-8 9-11 12-14 15-17 All 6-8 9-11 12-14 15-17
33.4 29.5 27.5 27.1 32.3 – 40.8 28.8 34.9 50.8 –
31.4 32.4 33.9 33.4 31.4 – 30.5 27.1 33.1 32.5* –
17.4 17.8 17.7 14.2 19.6 – 16.7 1.8 7.4 32.6 –
16.3 16.8 17.4 17.4 16.1 – 15.7 13.6* 17.6 16.3* –
*significantly different prevalence of at-risk for overweight or overweight between children with and without the condition, by chi-square, p<0.05.
(49.2% versus 29.5%, P <.01) and overweight (28.1% versus 14.5%, P <.01) than girls without physical limitations. Boys who had physical limitations also had higher prevalence of at-risk-for-overweight (52.5% versus 31.7%, P <.01) and were also more likely to be overweight, but the difference was of borderline significance (31.3% versus 16.9%, P 5 .09). Approximately 11% of children (10.7%; SE, 0.62) aged 6 to 15 years were receiving special education or early intervention services. The prevalence of at-risk-for-overweight was not significantly higher in children receiving special education services than children who did not receive special services (33.4% versus 31.4%, Table II). There was also 740
Bandini et al
no significant difference in the prevalence of overweight between children receiving and not receiving services (17.4% versus 16.3%). About 10% of respondents (9.6%; SE, 0.55) reported that a doctor or health professional had told them at some point that their child had attention deficit disorder. The prevalence of at-risk-for-overweight was not significantly higher in children with attention deficit disorder compared with children without attention deficit disorder (29.5% versus 31.6%, P 5 .58). Also, the prevalence of overweight among children with attention deficit disorder was similar to that of children without attention deficit disorder (14.5% versus The Journal of Pediatrics June 2005
Table III. Prevalence of at-risk-for-overweight (85th percentile) and overweight (95th percentile) by sex, age and condition (%): NHANES 1999-2002 Learning Disability At-Risk-For- Overweight (%) Sex Both Male
Female
Overweight (%)
Age (y)
With Learning Disability
No Learning Disability
With Learning Disability
No Learning Disability
All All 6-8 9-11 12-14 15-17 All 6-8 9-11 12-14 15-17
35.4 31.1 39.2 32.4 27.9 – 42.7 39.3 40.1 47.0 –
31.1 32.2 32.9 32.5 32.4 – 30.1* 26.6 32.3 32.3 –
21.9 20.7 22.8 21.0 20.0 – 23.8 13.9 19.9 29.4 –
15.7* 16.4 17.0 16.3 15.8 – 15.1* 13.0 16.5 16.1 –
*significantly different prevalence of at-risk for overweight or overweight between children with and without the condition, by chi-square, p<0.05.
16.5%). However, the prevalence of overweight was lower in boys with attention deficit disorder (12.7% versus 18.2%, P 5 .03). When stratified by sex and age group, a significantly lower prevalence of overweight was seen in boys aged 9 to 11 years (6.7% versus 18.6%, P 5 .02) and boys aged 12 to 14 years (7.6% versus 18.3%, P < .01). Also, in boys aged 12 to 14 years, there was a significantly lower prevalence of at-risk-foroverweight in boys with attention deficit disorder, compared with their peers (19.8% versus 33.9%, P 5 .04). There were no statistically significant differences in the prevalence of at-riskfor-overweight and overweight in girls with attention deficit/ hyperactivity disorder compared with girls without the disorder. About 12% (11.6%; SE, 0.78) of the children were identified as having a learning disability (LD). The prevalence of at-risk-for-overweight and overweight was higher in children with a LD compared to children without a LD (35.4% versus 31.1%, P 5 .06 and 21.9% versus 15.7%, P 5 .02, respectively; Table III). In sex-specific analyses, girls with a LD had a higher prevalence of both at-risk-for-overweight and overweight than girls without a LD (42.7% versus 30.1%, P <.01 and 23.8% versus 15.1%, P <.05, respectively). The prevalence of at-risk-for-overweight and overweight was not significantly different in boys with a LD compared with boys without a LD. Multivariate logistic regression analyses were undertaken to further characterize the observed relations (Table IV). In separate models, after adjustment for age, sex, and raceethnicity, receiving special education or early intervention services did not elevate the risk of at-risk-for-overweight or overweight. In contrast, children with limitations in physical activity were more than twice as likely to be at-risk-foroverweight and overweight when compared to peers without limitations. Also, girls with a LD were more likely to be Prevalence Of Overweight In Children With Developmental Disorders In The Continuous National Health And Nutrition Examination Survey (NHANES) 1999-2002
overweight compared with their peers without a LD. Boys with attention deficit disorder were less likely to be overweight than boys without attention deficit disorder, but these results were not significant (P <.11).
DISCUSSION The limited available literature on the prevalence of overweight in children with developmental disorders has been based on clinical observations and studies with small sample sizes. Although the high prevalence of overweight among children with genetically-related disabilities such as PraderWilli syndrome,7 Down Syndrome,8,9 congenital disabilities such as spina bifida,10-12 and some types of cerebral palsy10 is well documented, there is a need for representative data for children with other types of developmental disorders. We found that the prevalence of at-risk-for-overweight or overweight in children with certain developmental disorders was as high or higher than in children without developmental disorders. One of the difficulties in assessing the prevalence of overweight in children with developmental disorders is in the identification of these children, because of the broad variability in physical, developmental, and cognitive skills that characterize this population. In a previous analysis of the NHANES III survey, we restricted our analyses to 1 question, ‘‘Does your child have mental retardation?’’ We found that the prevalence of MR on the basis of this question was 0.38%,13 far less than estimates derived from other sources.14 Although we found no significant differences in the prevalence of overweight among children with and without MR, these findings were limited by the low prevalence of MR reported.13 In the NHANES 1999-2002 survey, 4% of children had physical limitations, 11% received special education or early 741
Table IV. Multivariate Logistic Regression Models Predicting Risk for Overweight and Overweight Adjusted Odds Ratios (95% CI) Risk for Overweight Limitations in physical activity* Special Education/Early Intervention* Attention Deficit Disorder - Males{ Attention Deficit Disorder - Females{ Learning Disability - Males{ Learning Disability - Females{
2.39 (1.67, 1.10 (0.86, 0.79 (0.47, 1.45 (0.90, 1.00 (0.71, 1.69 (1.20,
3.44) 1.41) 1.31) 2.34) 1.43) 2.39)
Overweight 2.29 1.08 0.70 1.47 1.41 1.70
(1.47, (0.76, (0.46, (0.84, (0.92, (1.06,
3.58) 1.55) 1.09) 2.60) 2.17) 2.74)
*odds ratio comparing children with the condition to those without the condition, adjusted for age (in months), sex, and race-ethnicity. {odds ratio comparing children with the condition to those without the condition, stratified by sex (sex by condition interaction, p-value<0.05), adjusted for age (in months) and race-ethnicity.
intervention services, 10% had an attention deficit disorder, and 12% had a LD. Of interest is our observation that boys with attention deficit disorder have a lower prevalence of overweight and at-risk-for-overweight in comparison with boys without attention deficit disorder, especially before the age of 15 years. In contrast, the prevalence of at-risk-foroverweight and overweight for girls with attention deficit/ hyperactivity disorder does not differ from girls without attention deficit/hyperactivity disorder. The difference in prevalence by sex among children with attention deficit/ hyperactivity disorder may reflect the differences in medication usage or tendency of girls with the disorder to have the inattentive type of the disorder, whereas boys are more likely to have the hyperactive/impulsive or combined types.15 Girls identified with attention deficit disorder may be more sedentary than their more physically active male counterparts, an observation worthy of future focused research. There are no earlier studies that have identified children with a LD as having a higher prevalence of overweight than typically developing children. In this study, we found a higher prevalence of both at-risk-for-overweight and overweight in girls with a LD. An explanation for why girls with a LD are at an increased risk for overweight is unclear. Learning disabilities represent a heterogeneous group of disorders, and within this sample there is no additional information with which these girls can be characterized. The finding that girls with a LD are more likely to be at risk for overweight than typically developing peers and that girls with attention deficit/ hyperactivity disorder are at higher risk for overweight than their male counterparts may suggest that being overweight in girls may be related to decreased physical activity levels. This warrants further investigation. Although a particular strength of the data summarized in this report derives from the representative nature of the source surveys, there are several limitations of our analyses that may undermine the validity of the prevalence estimates. The results in response to the question of overweight prevalence in children with limited activity need to be interpreted cautiously. Children with limitations in physical activity may have an altered body composition. This phenomenon has been observed among children with cerebral palsy and spinal 742
Bandini et al
bifida.10,16,17 The criteria for overweight used in this report were based on BMI, in accordance with current recommendations. Studies have not been conducted to establish the validity of BMI as a means of identifying overweight in children with physical disabilities. In addition, children who could not stand were not weighed, and therefore they are not included in the analysis. Thus, this category only represents children who are ambulatory, but have limitations that may interfere with movement. Therefore, children with severe physical limitations would not have been included in this analysis. These children are often underweight because of oral motor problems that affect feeding. Furthermore, children who have limitations in physical activity may not have developmental disorders (eg, children with acute medical problems). Thus, the findings that children with physical limitations are more likely to be overweight must be interpreted cautiously, because the sample may be heterogenous and will not include all children who have physical limitations. Nevertheless, the findings suggest that in children who have the ability to stand, limitations in physical activity increase their risk for being overweight. The NHANES 1999-2002 dataset begins to attempt to differentiate among groups of children with developmental disorders by querying about the specific problems of attention deficit disorder, special education, and a LD. However, these categories remain very broad, and important differences among children with different developmental disorders cannot be determined. Moreover, the prevalence of certain disorders, such as attention deficit/hyperactivity disorder, are reported to be higher than that reported in the literature,18 which may be caused by a reliance on parent report, or the question of whether the child had received a definitive diagnosis of attention deficit/hyperactivity disorder, or both. In addition, the pattern of significant results varies with age and may represent a true underlying phenomenon or random variation. Finally, parents of children with these limitations may decline participation in voluntary surveys like NHANES. Although children with developmental disorders are included in the volunteer sample, it is not clear whether special efforts are made to encourage families of children with disabilities to participate. The Journal of Pediatrics June 2005
Children with developmental disorders share the same risks for the sequelae of being overweight, such as type II diabetes mellitus, cardiovascular disease, orthopedic problems, and sleep apnea, as typically developing children.19 To reduce the likelihood of developing obesity-related secondary health conditions, educational and healthcare providers need to include this group of children in active health promotion efforts, including the provision of anticipatory guidance and specific counseling about the health risks of being overweight and obesity and the benefits of balanced nutrition and physical exercise. The finding of a high prevalence of overweight in children with developmental disorders emphasizes the importance of developing health promotion efforts for this population. Considerable research in this area is warranted for several reasons: (1) to better establish the prevalence of overweight in this population; (2) to elucidate the specific challenges that children with various developmental disorders face in the health promotion arena; and (3) to devise appropriate intervention strategies that take their particular needs into account.
REFERENCES 1. Hedley AA, Ogden CL, Johnson CL, Carroll MD, Curtin LR, Flegal KM. Prevalence of overweight and obesity among US children, adolescents, and adults, 1999-2002. JAMA 2004;291:2847-50. 2. US Public Health Service. Closing the Gap: A National Blueprint for Improving the Health of Individuals with Mental Retardation. Report of the Surgeon General’s Conference on Health Disparities in Mental Retardation. Washington, DC: US Department of Health and Human Services; 2002. 3. Centers for Disease Control. National Health and Nutrition Examination Survey (NHANES) 1999-2002. http://www.cdc.gov/nchs/nhanes.htm 2004. 4. Ogden CL, Kuczmarski RJ, Flegal KM, Mei Z, Guo S, Wei R, et al. Centers for Disease Control and Prevention 2000 growth charts for the United States: Improvements to the 1977 National Center for Health Statistics version. Pediatrics 2002;109(1):45-60.
Prevalence Of Overweight In Children With Developmental Disorders In The Continuous National Health And Nutrition Examination Survey (NHANES) 1999-2002
5. Barlow SE, Dietz WH. Obesity evaluation and treatment: expert committee recommendations. Pediatrics 1998;102:e29. 6. Centers for Disease Control. NHANES analytic guidelines, June 2004 Version. http://www.cdc.gov/nchs/data/nhanes/nhanes_general_guidelines_ june_04.pdf. 7. Holm VA, Cassidy SB, Butler MG, Hanchett JM, Greenswag LR, Whitman BY, et al. Prader-Willi Syndrome: consensus diagnostic criteria. Pediatrics 1993;91:398-402. 8. Prasher VP. Overweight and obesity amongst Down’s Syndrome adults. J Intellect Disabil Res 1995;39:437-41. 9. Rubin SS, Rimmer JH, Chicoine B, Braddock D, McGuire DE. Overweight prevalence in persons with Down Syndrome. Ment Retard 1998; 36:175-81. 10. Bandini LG, Schoeller DA, Fukagawa NK, Wykes LJ, Dietz WH. Body composition and energy expenditure in adolescents with cerebral palsy or myelodysplasia. Pediatr Res 1991;29:70-7. 11. Shepherd K, Roberts DW, Golding S, Thomas BJ, Shepherd RW. Body composition in myelomeningocele. Am J Clin Nutr 1991;53:1-6. 12. Hayes-Allen MC, Tring FC. Obesity: another hazard for spina bifida children. Br J Prev Soc Med 1973;27:192-6. 13. Bandini LG, Curtin C, Tybor DJ, Hamad C, Must A. Prevalence of overweight among children with mental retardation based on nationally representative surveys. Obes Res 2003;11S:A120. 14. Larson S, Lakin C, Anderson LA, Kwak N, Lee JH, Anderson DA. Prevalence of mental retardation and/or developmental disabilities: analysis of the 1994/1995 HNIS-D. Minneapolis: Research and Training Center on Community Living, Institute on Community Integration, University of Minnesota; 2000. 15. Biederman J, Mick E, Faranoe SV, Braaten E, Doyle A, Spencer T, et al. Influence of gender on attention deficit hyperactivity disorder in children referred to a psychiatric clinic. Am J Psychiatry 2002;159:36-42. 16. Stallings VA, Cronk CE, Zemel BS, Charney EB. Body composition in children with spastic quadriplegic cerebral palsy. J Pediatr 1995;126: 833-9. 17. van den Berg-Emons RJG, van Baak MA, Westerterp KR. Are skinfold measurement suitable to compare body fat between children with spastic cerebral palsy and healthy controls? Dev Med Child Neurol 1998;40: 335-9. 18. Diagnosis and treatment of attention deficit hyperactivity disorder. NIH Consensus Statement Online 1998 Nov 16-18; [10/28/04];16:1-37. 19. Must A, Strauss RS. Risks and consequences of childhood and adolescent obesity. Int J Obes 1999;23S:S2-11.
743
Objective To estimate the prevalence of overweight in children identified with developmental disorders on the basis of nationally representative survey data. Study design We estimated the prevalence of overweight in children with developmental disorders on the basis of a recent large nationally representative survey. The continuous National Health and Nutrition Examination Survey (NHANES) 1999-2002 included 4 questions to identify children with developmental disorders. Height and weight were used to calculate body mass index (BMI). BMI percentiles were estimated relative to the age- and sex-specific Centers for Disease Control and Prevention growth reference. The 85th percentile BMI defined at-risk-for-overweight and the 95th percentile BMI defined overweight. Results We found a higher prevalence of at-risk-for overweight and overweight among children with limitations in physical activity and a higher prevalence of overweight in girls with learning disabilities, compared with children without these conditions, after adjustment for age and race-ethnicity. Conclusion To the extent that children with developmental disorders are included in large representative surveys, the data suggest that children with developmental disorders have a risk for overweight that is at least as great as that of typically developing children. (J Pediatr 2005;146:738-43) he prevalence of overweight among US children has been escalating.1 Little has been done to determine the prevalence of and risk factors for obesity in children with developmental disorders, in this case, children who have physical limitations, learning disabilities, attention disorders, and those who receive special education services. The importance of this inquiry was underscored by a conference convened in 2001 by the Surgeon General that addressed the health needs of individuals with mental retardation (MR) and developmental disabilities.2 The conference report called for research and clinical intervention to address the specific health needs of persons with MR and to develop health promotion programs that seek to improve their overall health and wellness. In this study, we used data derived from a recent nationally representative survey, the National Health and Nutrition Examination Survey (NHANES) 1999-2002, to estimate From University of Massachusetts Medical School, Eunice Kennedy the prevalence of overweight in children with developmental disorders. Measured heights Shriver Center, Waltham, Massachu3 and weights from the NHANES 1999-2002 survey were used to estimate the prevalence setts; Boston University, Boston, Massachusetts; Friedman School of of at-risk for overweight or overweight in children with developmental disorders. We Nutrition Science and Policy, Tufts hypothesized that children with developmental disorders would be at higher risk for University, Boston, Massachusetts; and Department of Public Health overweight than their typically developing peers. The complex medical, physical, and and Family Medicine, Tufts University psychosocial difficulties that these children encounter may put them at higher risk for School of Medicine, Boston, Massaobesity. For example, dietary factors such as the use of food as a behavioral reinforcer or chusetts. Submitted for publication Aug 9, mealtime behaviors that influence food choices or parental meal preparation may lead to an 2004; last revision received Nov 24, energy imbalance. Lack of participation in physical activity opportunities because of a lack 2004; accepted Jan 25, 2005. of inclusion in team sports, poor coordination, and/or social isolation may contribute to Reprint requests: Linda G. Bandini, PhD, RD, University of Massachusetts positive energy balance and, in time, to increased weight gain. Furthermore, because of the Medical School, Eunice Kennedy numerous physiological, social, and educational demands and stresses associated with Shriver Center, 200 Trapelo Rd, raising a child with a developmental disorder, weight control may not be a priority for the Waltham, MA 02452. E-mail: Linda.
T
BMI CDC LD
738
Body mass index Centers for Disease Control and Prevention Learning disability
MR NHANES
Mental retardation National Health and Nutrition Examination Survey
[email protected]. 0022-3476/$ - see front matter Copyright ª 2005 Elsevier Inc. All rights reserved. 10.1016/j.jpeds.2005.01.049
families of these children. In this report, we estimated the prevalence of overweight in children with physical limitations, children receiving special education or early intervention services, and children with attention deficit disorder or learning disabilities. We also explored whether the prevalence of overweight varied by age and sex.
Disease Control and Prevention (CDC) growth reference standards.4 We adopted CDC terminology to define at-riskfor-overweight and overweight. At-risk-for-overweight is defined as a BMI >85th percentile and overweight is defined as a BMI >95th percentile.5
Statistical Analyses
METHODS NHANES is a series of national examination studies conducted in the United States since 1970. After the NHANES III 1988-1994 survey, the periodic examination surveys became a ‘‘continuous’’ survey. Since 1999, data have been collected every 2 years from a representative sample of the US population; approximately 7000 subjects from different locations are sampled. In the basic protocol for all these surveys, randomly selected subjects are first interviewed in their homes, and information on demographics, socioeconomic status, diet, and health-related questions are obtained. In a mobile examination center, body weight and height are measured with a standard protocol. Weight is measured to 2 decimal places with an electronic-load cell scale in kilograms; height is measured with a fixed stadiometer. Children who are unable to stand are not weighed and therefore are not included in this analysis. Unfortunately, the number of children not weighed for this reason is not available from the public use dataset. Survey items from the 1999-2002 NHANES identified children with developmental disorders. Because of the dearth of this information in comprehensive nationally representative surveys, we selected questions that would suggest that the child had a developmental disorder. We limited our analyses to children aged 6.0 to 17.9 years to reflect the school-age years of typically developing children. Although many children who receive special education services remain in high school until the age of 22 years, they were not included in our analysis because the data on reference children would not be comparable. The NHANES 1999-2002 combined survey has an examination sample size of 19,759. Details of the sampling design and survey elements are available.3 In the continuing survey, we selected 4 questions that identified children with developmental disorders as follows: (1) children with physical limitations; (2) children receiving special education or early intervention services; (3) children with attention deficit disorder; and (4) children with learning disabilities. (Appendix; available online at http://www.us.elsevierhealth. com/jpeds). Items that identified children receiving special education services and children with a learning disability were asked only of children aged 6 to 14.9 years.
Criteria for Overweight Body mass index (BMI) was calculated from measures of height and weight (kg/m2) and used to identify overweight. To provide a measure of relative weight, a BMI z-score was calculated for each BMI measure, with the reference to ageand sex-specific parameters provided by the Centers for Prevalence Of Overweight In Children With Developmental Disorders In The Continuous National Health And Nutrition Examination Survey (NHANES) 1999-2002
For each survey, the analytic dataset consisted of all children with a measured height and weight whose parents responded to the identified survey items. Prevalence of at-riskfor-overweight and overweight were estimated for the entire population and for individuals with a positive response to the questions about developmental disorders. We tested the statistical significance of the differences in prevalence by group using chi-square tests. Multivariate logistic regression analysis was undertaken to estimate the relative risk of at-risk-for overweight and overweight (and their 95% confidence limits) for children with developmental disorders compared to children not identified as having developmental disorders, after controlling for age, sex, and race-ethnicity. Racial-ethnic categories were constructed for non-Hispanic white, non-Hispanic black, Hispanic, and other. Interactions were tested between each condition and sex; when the interaction term was statistically significant, results were stratified by sex. Data were analyzed using SAS software (version 8.02; SAS Institute, Cary, NC) and SUDAAN software (version 8.0, Research Triangle Institute, Cary, NC). We included 4-year sample weights to adjust for unequal selection probabilities and over-sampling in the complex samples. In the combined NHANES 1999-2002, masked variance units as pseudo-primary sampling units were used, as recommended.6 When the P value was <.05, results were deemed to be statistically significant.
RESULTS In the NHANES 1999-2002 dataset, 4 questions identified 1128 children with developmental disorders. Specifically, items identified children with physical limitations, attention deficit disorder, learning disability, and those receiving special education or early intervention services. Of the 1128 children, 654 (57.9%) had 1 of these conditions, 327 (28.9%) had 2 of these conditions, 133 (11.8%) had 3 of these conditions, and 14 (1.2%) had all 4 of these conditions. The most frequent coexisting diagnoses were that 40.4% and 31.8% of children with learning disabilities and attention deficit disorder, respectively, also received special education services. The percentage of children aged 6 to 17 years with health problems that limit their ability to walk play or run was 4.1% (SE, 0.38). Children with these physical activity limitations were significantly more likely to be at-risk-foroverweight than those without physical activity limitations (50.9% versus 30.6%, P <.001, Table I). These children were also more likely to be overweight (29.7% versus 15.7%, P <.01). In sex-specific analyses, girls with physical limitations had a significantly higher prevalence of at-risk-for-overweight 739
Table I. Prevalence of at-risk-for-overweight (85th percentile) and overweight (95th percentile) by sex, age and condition (%): NHANES 1999-2002 Limitations in Crawling, Walking, Running, and Playing At-Risk-For- Overweight (%) Sex
Overweight (%)
Age (y)
With limitations
No limitations
With limitations
No limitations
All All 6-8 9-11 12-14 15-17 All 6-8 9-11 12-14 15-17
50.9 52.5 85.9 52.7 50.3 32.2 49.2 44.9 63.8 62.8 24.7
30.6* 31.7* 31.7 31.7 30.6 32.9 29.5* 26.9 32.3* 32.1* 26.8
29.7 31.3 56.3 24.0 27.3 24.7 28.1 38.2 38.8 24.5 22.0
15.7* 16.9 16.3 16.6 16.1 18.9 14.5* 12.5 16.0* 17.2 12.5
Both Male
Female
*significantly different prevalence of at-risk for overweight or overweight between children with and without the condition, by chi-square, p<0.05.
Table II. Prevalence of at-risk-for-overweight (85th percentile) and overweight (95th percentile) by sex, age and condition (%): NHANES 1999-2002 Enrollment in Special Education Services or Early Intervention (EI) At-Risk-For- Overweight (%) Sex Both Male
Female
Overweight (%)
Age (y)
Enrolled in Special Education/EI
Not Enrolled in Special Education/EI
Enrolled in Special Education/EI
Not Enrolled in Special Education/EI
All All 6-8 9-11 12-14 15-17 All 6-8 9-11 12-14 15-17
33.4 29.5 27.5 27.1 32.3 – 40.8 28.8 34.9 50.8 –
31.4 32.4 33.9 33.4 31.4 – 30.5 27.1 33.1 32.5* –
17.4 17.8 17.7 14.2 19.6 – 16.7 1.8 7.4 32.6 –
16.3 16.8 17.4 17.4 16.1 – 15.7 13.6* 17.6 16.3* –
*significantly different prevalence of at-risk for overweight or overweight between children with and without the condition, by chi-square, p<0.05.
(49.2% versus 29.5%, P <.01) and overweight (28.1% versus 14.5%, P <.01) than girls without physical limitations. Boys who had physical limitations also had higher prevalence of at-risk-for-overweight (52.5% versus 31.7%, P <.01) and were also more likely to be overweight, but the difference was of borderline significance (31.3% versus 16.9%, P 5 .09). Approximately 11% of children (10.7%; SE, 0.62) aged 6 to 15 years were receiving special education or early intervention services. The prevalence of at-risk-for-overweight was not significantly higher in children receiving special education services than children who did not receive special services (33.4% versus 31.4%, Table II). There was also 740
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no significant difference in the prevalence of overweight between children receiving and not receiving services (17.4% versus 16.3%). About 10% of respondents (9.6%; SE, 0.55) reported that a doctor or health professional had told them at some point that their child had attention deficit disorder. The prevalence of at-risk-for-overweight was not significantly higher in children with attention deficit disorder compared with children without attention deficit disorder (29.5% versus 31.6%, P 5 .58). Also, the prevalence of overweight among children with attention deficit disorder was similar to that of children without attention deficit disorder (14.5% versus The Journal of Pediatrics June 2005
Table III. Prevalence of at-risk-for-overweight (85th percentile) and overweight (95th percentile) by sex, age and condition (%): NHANES 1999-2002 Learning Disability At-Risk-For- Overweight (%) Sex Both Male
Female
Overweight (%)
Age (y)
With Learning Disability
No Learning Disability
With Learning Disability
No Learning Disability
All All 6-8 9-11 12-14 15-17 All 6-8 9-11 12-14 15-17
35.4 31.1 39.2 32.4 27.9 – 42.7 39.3 40.1 47.0 –
31.1 32.2 32.9 32.5 32.4 – 30.1* 26.6 32.3 32.3 –
21.9 20.7 22.8 21.0 20.0 – 23.8 13.9 19.9 29.4 –
15.7* 16.4 17.0 16.3 15.8 – 15.1* 13.0 16.5 16.1 –
*significantly different prevalence of at-risk for overweight or overweight between children with and without the condition, by chi-square, p<0.05.
16.5%). However, the prevalence of overweight was lower in boys with attention deficit disorder (12.7% versus 18.2%, P 5 .03). When stratified by sex and age group, a significantly lower prevalence of overweight was seen in boys aged 9 to 11 years (6.7% versus 18.6%, P 5 .02) and boys aged 12 to 14 years (7.6% versus 18.3%, P < .01). Also, in boys aged 12 to 14 years, there was a significantly lower prevalence of at-risk-foroverweight in boys with attention deficit disorder, compared with their peers (19.8% versus 33.9%, P 5 .04). There were no statistically significant differences in the prevalence of at-riskfor-overweight and overweight in girls with attention deficit/ hyperactivity disorder compared with girls without the disorder. About 12% (11.6%; SE, 0.78) of the children were identified as having a learning disability (LD). The prevalence of at-risk-for-overweight and overweight was higher in children with a LD compared to children without a LD (35.4% versus 31.1%, P 5 .06 and 21.9% versus 15.7%, P 5 .02, respectively; Table III). In sex-specific analyses, girls with a LD had a higher prevalence of both at-risk-for-overweight and overweight than girls without a LD (42.7% versus 30.1%, P <.01 and 23.8% versus 15.1%, P <.05, respectively). The prevalence of at-risk-for-overweight and overweight was not significantly different in boys with a LD compared with boys without a LD. Multivariate logistic regression analyses were undertaken to further characterize the observed relations (Table IV). In separate models, after adjustment for age, sex, and raceethnicity, receiving special education or early intervention services did not elevate the risk of at-risk-for-overweight or overweight. In contrast, children with limitations in physical activity were more than twice as likely to be at-risk-foroverweight and overweight when compared to peers without limitations. Also, girls with a LD were more likely to be Prevalence Of Overweight In Children With Developmental Disorders In The Continuous National Health And Nutrition Examination Survey (NHANES) 1999-2002
overweight compared with their peers without a LD. Boys with attention deficit disorder were less likely to be overweight than boys without attention deficit disorder, but these results were not significant (P <.11).
DISCUSSION The limited available literature on the prevalence of overweight in children with developmental disorders has been based on clinical observations and studies with small sample sizes. Although the high prevalence of overweight among children with genetically-related disabilities such as PraderWilli syndrome,7 Down Syndrome,8,9 congenital disabilities such as spina bifida,10-12 and some types of cerebral palsy10 is well documented, there is a need for representative data for children with other types of developmental disorders. We found that the prevalence of at-risk-for-overweight or overweight in children with certain developmental disorders was as high or higher than in children without developmental disorders. One of the difficulties in assessing the prevalence of overweight in children with developmental disorders is in the identification of these children, because of the broad variability in physical, developmental, and cognitive skills that characterize this population. In a previous analysis of the NHANES III survey, we restricted our analyses to 1 question, ‘‘Does your child have mental retardation?’’ We found that the prevalence of MR on the basis of this question was 0.38%,13 far less than estimates derived from other sources.14 Although we found no significant differences in the prevalence of overweight among children with and without MR, these findings were limited by the low prevalence of MR reported.13 In the NHANES 1999-2002 survey, 4% of children had physical limitations, 11% received special education or early 741
Table IV. Multivariate Logistic Regression Models Predicting Risk for Overweight and Overweight Adjusted Odds Ratios (95% CI) Risk for Overweight Limitations in physical activity* Special Education/Early Intervention* Attention Deficit Disorder - Males{ Attention Deficit Disorder - Females{ Learning Disability - Males{ Learning Disability - Females{
2.39 (1.67, 1.10 (0.86, 0.79 (0.47, 1.45 (0.90, 1.00 (0.71, 1.69 (1.20,
3.44) 1.41) 1.31) 2.34) 1.43) 2.39)
Overweight 2.29 1.08 0.70 1.47 1.41 1.70
(1.47, (0.76, (0.46, (0.84, (0.92, (1.06,
3.58) 1.55) 1.09) 2.60) 2.17) 2.74)
*odds ratio comparing children with the condition to those without the condition, adjusted for age (in months), sex, and race-ethnicity. {odds ratio comparing children with the condition to those without the condition, stratified by sex (sex by condition interaction, p-value<0.05), adjusted for age (in months) and race-ethnicity.
intervention services, 10% had an attention deficit disorder, and 12% had a LD. Of interest is our observation that boys with attention deficit disorder have a lower prevalence of overweight and at-risk-for-overweight in comparison with boys without attention deficit disorder, especially before the age of 15 years. In contrast, the prevalence of at-risk-foroverweight and overweight for girls with attention deficit/ hyperactivity disorder does not differ from girls without attention deficit/hyperactivity disorder. The difference in prevalence by sex among children with attention deficit/ hyperactivity disorder may reflect the differences in medication usage or tendency of girls with the disorder to have the inattentive type of the disorder, whereas boys are more likely to have the hyperactive/impulsive or combined types.15 Girls identified with attention deficit disorder may be more sedentary than their more physically active male counterparts, an observation worthy of future focused research. There are no earlier studies that have identified children with a LD as having a higher prevalence of overweight than typically developing children. In this study, we found a higher prevalence of both at-risk-for-overweight and overweight in girls with a LD. An explanation for why girls with a LD are at an increased risk for overweight is unclear. Learning disabilities represent a heterogeneous group of disorders, and within this sample there is no additional information with which these girls can be characterized. The finding that girls with a LD are more likely to be at risk for overweight than typically developing peers and that girls with attention deficit/ hyperactivity disorder are at higher risk for overweight than their male counterparts may suggest that being overweight in girls may be related to decreased physical activity levels. This warrants further investigation. Although a particular strength of the data summarized in this report derives from the representative nature of the source surveys, there are several limitations of our analyses that may undermine the validity of the prevalence estimates. The results in response to the question of overweight prevalence in children with limited activity need to be interpreted cautiously. Children with limitations in physical activity may have an altered body composition. This phenomenon has been observed among children with cerebral palsy and spinal 742
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bifida.10,16,17 The criteria for overweight used in this report were based on BMI, in accordance with current recommendations. Studies have not been conducted to establish the validity of BMI as a means of identifying overweight in children with physical disabilities. In addition, children who could not stand were not weighed, and therefore they are not included in the analysis. Thus, this category only represents children who are ambulatory, but have limitations that may interfere with movement. Therefore, children with severe physical limitations would not have been included in this analysis. These children are often underweight because of oral motor problems that affect feeding. Furthermore, children who have limitations in physical activity may not have developmental disorders (eg, children with acute medical problems). Thus, the findings that children with physical limitations are more likely to be overweight must be interpreted cautiously, because the sample may be heterogenous and will not include all children who have physical limitations. Nevertheless, the findings suggest that in children who have the ability to stand, limitations in physical activity increase their risk for being overweight. The NHANES 1999-2002 dataset begins to attempt to differentiate among groups of children with developmental disorders by querying about the specific problems of attention deficit disorder, special education, and a LD. However, these categories remain very broad, and important differences among children with different developmental disorders cannot be determined. Moreover, the prevalence of certain disorders, such as attention deficit/hyperactivity disorder, are reported to be higher than that reported in the literature,18 which may be caused by a reliance on parent report, or the question of whether the child had received a definitive diagnosis of attention deficit/hyperactivity disorder, or both. In addition, the pattern of significant results varies with age and may represent a true underlying phenomenon or random variation. Finally, parents of children with these limitations may decline participation in voluntary surveys like NHANES. Although children with developmental disorders are included in the volunteer sample, it is not clear whether special efforts are made to encourage families of children with disabilities to participate. The Journal of Pediatrics June 2005
Children with developmental disorders share the same risks for the sequelae of being overweight, such as type II diabetes mellitus, cardiovascular disease, orthopedic problems, and sleep apnea, as typically developing children.19 To reduce the likelihood of developing obesity-related secondary health conditions, educational and healthcare providers need to include this group of children in active health promotion efforts, including the provision of anticipatory guidance and specific counseling about the health risks of being overweight and obesity and the benefits of balanced nutrition and physical exercise. The finding of a high prevalence of overweight in children with developmental disorders emphasizes the importance of developing health promotion efforts for this population. Considerable research in this area is warranted for several reasons: (1) to better establish the prevalence of overweight in this population; (2) to elucidate the specific challenges that children with various developmental disorders face in the health promotion arena; and (3) to devise appropriate intervention strategies that take their particular needs into account.
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5. Barlow SE, Dietz WH. Obesity evaluation and treatment: expert committee recommendations. Pediatrics 1998;102:e29. 6. Centers for Disease Control. NHANES analytic guidelines, June 2004 Version. http://www.cdc.gov/nchs/data/nhanes/nhanes_general_guidelines_ june_04.pdf. 7. Holm VA, Cassidy SB, Butler MG, Hanchett JM, Greenswag LR, Whitman BY, et al. Prader-Willi Syndrome: consensus diagnostic criteria. Pediatrics 1993;91:398-402. 8. Prasher VP. Overweight and obesity amongst Down’s Syndrome adults. J Intellect Disabil Res 1995;39:437-41. 9. Rubin SS, Rimmer JH, Chicoine B, Braddock D, McGuire DE. Overweight prevalence in persons with Down Syndrome. Ment Retard 1998; 36:175-81. 10. Bandini LG, Schoeller DA, Fukagawa NK, Wykes LJ, Dietz WH. Body composition and energy expenditure in adolescents with cerebral palsy or myelodysplasia. Pediatr Res 1991;29:70-7. 11. Shepherd K, Roberts DW, Golding S, Thomas BJ, Shepherd RW. Body composition in myelomeningocele. Am J Clin Nutr 1991;53:1-6. 12. Hayes-Allen MC, Tring FC. Obesity: another hazard for spina bifida children. Br J Prev Soc Med 1973;27:192-6. 13. Bandini LG, Curtin C, Tybor DJ, Hamad C, Must A. Prevalence of overweight among children with mental retardation based on nationally representative surveys. Obes Res 2003;11S:A120. 14. Larson S, Lakin C, Anderson LA, Kwak N, Lee JH, Anderson DA. Prevalence of mental retardation and/or developmental disabilities: analysis of the 1994/1995 HNIS-D. Minneapolis: Research and Training Center on Community Living, Institute on Community Integration, University of Minnesota; 2000. 15. Biederman J, Mick E, Faranoe SV, Braaten E, Doyle A, Spencer T, et al. Influence of gender on attention deficit hyperactivity disorder in children referred to a psychiatric clinic. Am J Psychiatry 2002;159:36-42. 16. Stallings VA, Cronk CE, Zemel BS, Charney EB. Body composition in children with spastic quadriplegic cerebral palsy. J Pediatr 1995;126: 833-9. 17. van den Berg-Emons RJG, van Baak MA, Westerterp KR. Are skinfold measurement suitable to compare body fat between children with spastic cerebral palsy and healthy controls? Dev Med Child Neurol 1998;40: 335-9. 18. Diagnosis and treatment of attention deficit hyperactivity disorder. NIH Consensus Statement Online 1998 Nov 16-18; [10/28/04];16:1-37. 19. Must A, Strauss RS. Risks and consequences of childhood and adolescent obesity. Int J Obes 1999;23S:S2-11.
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