Our data from this chart review suggest that as for the general population of children in the US, overweight represents a problem among children with ADHD and ASD. The prevalence of at-risk-for-overweight (BMI ≥ 85th percentile) and overweight (BMI ≥ 95th percentile) was 29% and 17.3% respectively in children with ADHD. For children with ASD, the overall prevalence of at-risk-for-overweight was 35.7% and prevalence of overweight was 19%.
The literature on obesity in children with ADHD is sparse. Historically, inquiries into weight status of children with ADHD have focused on the potential for growth suppression associated with the use of stimulant medication. More recently, however, some research has been conducted to examine the prevalence of overweight in children with ADHD. Anderson et al. [13
] reported an association of increased relative weight among girls with ADHD but not boys in a community-based sample. Holtkamp et al. [14
] evaluated a sample of 97 boys with ADHD in Germany to test the hypothesis that hyperactive boys would have a lower prevalence of obesity than an age-matched healthy male reference population. Contrary to expectations, they found that a significant number of subjects with ADHD had a BMI ≥ 90th
percentile (19.6%) and 7.2% had a BMI ≥ 97th
percentile using the higher International Obesity Task Force cut-offs points. Altfas et al. [15
] conducted a chart review of 215 adults seen in a weight control clinic. Among these patients, 90% of whom were female, 27.4% had ADHD, 33.5% had symptoms and behaviors of ADHD but did not meet formal diagnostic criteria, and 39.1% did not have ADHD. All of the patients with ADHD were classified as having the inattentive type of the disorder. Of those patients with a BMI ≥ 40, 42.6% had ADHD. The authors noted that patients with ADHD were less successful at losing weight than those without ADHD. In a recent study of 26 children, hospitalized for obesity (BMI>85%) (mean age 13), Agranat-Meged et al. [16
] found that 15 of these children had ADHD. Nine of these children had not been diagnosed prior to the study. Ten of the 13 boys and 5 of the 13 girls were found to have ADHD. Of the 15 children with ADHD, 9 had the combined type of ADHD and 6 had the inattentive type. Although this study suggests a relation between ADHD and obesity, the number of patients was relatively small and the study lacked a comparison group.
Although the criteria for overweight may differ among studies, our data and the reported data to date suggest that overweight is a problem among children with ADHD. Furthermore, the data reported by Altfas et al. and Agranat-Meged et al. underscore the importance of understanding and preventing the problem of overweight in children with ADHD, before they become adults.
The children in our study taking stimulant medication were half as likely to be overweight as those not on these medications however, none of the children in our sample who took stimulant medication were underweight. Reports in the literature of the effects of stimulant medication on weight status are equivocal; for example, one study found weight loss among children taking stimulant medication [17
] whereas another found no weight deficits [18
Only a few studies have reported data on weight status of children with ASD. In one recent report, Mouridsen et al. [19
] examined the weight status of 117 young Danish children with autism. Body mass index (BMI) for males but not for females was significantly lower than an age-matched reference population. In Germany, a low BMI has been reported in 13 children with Asperger's syndrome [20
]. In a large study of 20,031 Japanese children and adolescents with mental retardation (6–17 yrs) that included 413 children with autism, the prevalence of obesity was reported to be 22% in boys and 11% in girls. No data were available to assess the prevalence among different age groups and obesity was defined from measures of standard weight for height [21
]. Another study of 140 Japanese children 7–18 years of age with autism revealed that 25% of the children were classified as obese [22
]. The variability in the prevalence estimates among children with autism from different countries may be explained by different environmental factors that contribute to the development of overweight. In addition, different definitions of obesity, the diagnostic category, or mode of recruitment into the studies may contribute to observed differences. Nonetheless, these data support our findings that overweight is as significant a problem in children with autism as in the general population.
For children with ASD, unusual dietary patterns and decreased access to opportunities for physical activity may be factors that contribute to overweight. Rosser and Frey [23
] report less time spent in moderate activity in children with ASD compared to children without ASD. Opportunities to engage in structured activities may be limited and may further decline with age for children with ASD. In our study, although the numbers in each age group are small, we observed a trend toward increasing prevalence of overweight with increasing age for children with ASD. Further research is needed to determine whether the prevalence of obesity in children with ASD increases with age and whether differences in eating and activity patterns contribute to overweight. Identification of specific environmental factors that are associated with increasing the risk for overweight (e.g., access to physical activity programs, time spent in sedentary behavior) are important areas of research that will help direct efforts at health promotion and disease prevention for this population of children.
Our study data were obtained from a chart review at a tertiary care clinic, hence, the data gathered represent children from a special population. Therefore, our findings may not be generalizable to the broader community of children with ADHD, and should be considered preliminary. Furthermore, because we relied on clinically derived diagnoses of ADHD and ASD rather than on objective, standardized measures, we are unable to determine the diagnostic homogeneity of the clinical charts reviewed. We chose to look at data at the initial visit, thus additional diagnostic information that may have surfaced on subsequent visits, such as the presence of depression, a known risk factor in ADHD was unavailable. Because depression is a frequent co-morbidity in children with ADHD and has been shown to be related to obesity [24
] depression may have been a confounding factor. Thus, larger studies of children with ADHD and ASD adjusting for co-morbid conditions need to be carried out to elucidate further these findings. Finally, the number of charts reviewed was small, so our prevalence estimates lack a high degree of precision.