The purpose of this multi-center observational study (utilizing the sites enrolling patients for the Pediatric Adenotonsillectomy Trial for Snoring (PATS) [1U011HL125307-O1A1]) is to gather data regarding children with Down syndrome (DS) and Sleep Disordered Breathing (SDB) referred for treatment with adenotonsillectomy to inform a future randomized controlled trial in this population.

Down syndrome (DS) is associated with a wide range of neurobehavioral and physical morbidities. Obstructive sleep apnea (OSA) is prevalent in children with DS and causes a myriad of physiological stresses that may exacerbate neurobehavioral and cardiac morbidities. Improving sleep health thus provides a modifiable intervention target for improving behavior, cognition, quality of life, and physical health of children with DS. However, critical knowledge gaps limit the adoption and implementation of effective OSA interventions, resulting in practice variability and suboptimal treatment of OSA across the spectrum of DS. In particular, it is in unclear how to select candidates likely to benefit from adenotonsillectomy (AT) and how to utilize information from polysomnographic, clinical, and demographic parameters to predict children most likely to benefit from AT compared to alternative treatments or to watchful waiting. The goal of this study is to collect the necessary data to plan and execute a future pivotal RCT of the role of OSA treatment in the care of children with DS. This study will provide critical information on the methodological approaches for conducting such a randomized controlled clinical trial (RCT), informing the appropriate recruitment strategies, patient population and outcome measures for a future clinical trial. The investigators will leverage expertise in pediatric sleep medicine, clinical trials, neuropsychology, and DS as well as the PATS clinical trials infrastructure to catalyze a new DS clinical research initiative. Our proposed next steps are to enroll in an observational study at active PATS centers 50 children with DS who are referred for clinically indicated evaluation and treatment of OSA. At baseline and 6 months following AT, these children will undergo systematic assessments of sleep, behavior, cognition, daytime functioning, and quality of life, generating key data to inform the design of a later pivotal RCT.

Healthy Sleep for Children with Down Syndrome (HELP-DS) intends to take advantage of a successful collaboration of leaders in sleep medicine, otolaryngology and clinical trials to efficiently leverage experiences from the The Childhood Adenotonsillectomy Trial (CHAT) as well as the current resources of the PATS trial to collect data for the evaluation of key questions needed to design a future RCT, including approaches related to the selection of participating sites, the patient population to receive the intervention, and outcome measurements.

The primary objective of HELP-DS to determine the feasibility of recruiting and retaining individuals in an observational study of AT across multiple clinical sites.

Secondary objectives are:

1. Evaluate the feasibility of collecting a range of baseline and outcome data, and specifically the ability of children to perform neurobehavioral assessments (GoNoGo, pegboard task).
2. Understand issues related to patient preference, equipoise, and barriers to treatment. The investigators will track how many children referred for AT actually undergo surgery, the time interval between referral and surgery, other interventions pursued, and factors such as insurance, socio-economic factors, and cultural norms, that associate with family-decision making.
3. Examine the consistency and completeness of Healthcare Utilization (HCU) data extracted across our sites, describing differences by recruitment site, health, system characteristics, insurance-related factors, etc. The investigators will estimate incidence rates of HCU events for hospital admissions, emergency department/unscheduled office visits, specialty consultations and medication use during the 6 months following surgery and compare rates to those for the year prior to surgery.

These aims have substantial public health significance given the high morbidity of Down syndrome and sleep-disordered breathing in children.

Inclusion Criteria:

• DS diagnosis regardless of genetic status (e.g., mosaicism or translocation).
• Aged >3 to <13 years at the date of consent.
• Primary indication for AT is nocturnal obstructive symptoms (i.e., not recurrent infections or other indications).
• Deemed to be a candidate for AT by Ear, Nose and Throat (ENT) evaluation; that is, no technical issues that would be a contraindication for surgery such as submucous cleft palate.

Exclusion Criteria:

• Prior tonsillectomy (partial or complete).
• Severe chronic health conditions that would contradict surgery (severe morbid obesity, unrepaired cyanotic congenital heart disease, bleeding disorders).
• Severe behavioral problems that would preclude participation in the study's testing procedures (PSG, actigraphy).
• Severe OSA with respiratory failure needing urgent/emergent management
• Plan to undergo additional airway surgery at the time of AT.
• Caregiver/child planning to move out of the area within 6 months.
• Caregiver/child does not speak English or Spanish well enough to complete the behavioral and performance measures.
• Child in foster care.

Dyads of caregivers and children with DS aged 3-13 years diagnosed with SDB and referred for treatment with adenotonsillectomy (AT) will be recruited.