Associations of Down Syndrome with Autism Spectrum Disorder and Attention Deficit/ Hyperactivity Disorder Among Children and Adolescents.

Children with Down syndrome (DS) are more likely to be diagnosed with co-existing conditions, such as autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD). However, the correlation has not been fully delineated to date. Our study aimed to examine the associations of DS with ASD and ADHD in children and adolescents using a national population-based database. In this cross-sectional study, we included a total of 214,300 children aged 3-17 years from the National Health Interview Survey. Physician-diagnosed DS, ASD and ADHD were reported during an in-person household interview. Logistic regression with survey sampling weights was used to estimate the odds ratios (ORs) of ASD and ADHD, along with 95% confidence intervals (CIs). Among the 214,300 children, 329 were identified as having DS. Among those, 21 children were diagnosed with ASD, 48 with ADHD, and 6 exhibited co-existing ASD and ADHD. After adjusting for demographic factors, compared to those without DS, the ORs of ASD, ADHD and the co-occurrence of ASD and ADHD in children with DS were 5.40 (95% CI: 3.04-9.59), 1.72 (95% CI: 1.17-2.53), and 3.45(95% CI:1.29-9.20), respectively. Stratified analysis revealed that significant associations of DS with ASD and ADHD were detected for both male and female, but an interaction effect was only observed between sex and ASD (P < 0.001). Our study confirmed that children with DS are more likely to have comorbidities of ASD and ADHD than the general population, and these comorbidities may vary by sex.