Administrative supplement

Abstract Down syndrome (DS) is associated with an elevated likelihood of co-occurring neurodevelopmental conditions, including autism spectrum disorder (ASD). Although dimensions like sleep and brain activity are considered critical areas of interest in the investigation of nonsyndromic ASD, these physiological dimensions have not been characterized to date in co-occurring DS and ASD. This Administrative Supplement will expand the scope of R01HD110542 (Autism in Young Children with Down Syndrome) to evaluate the feasibility of collecting physiological measures of sleep and neural function in young children with DS, and their potential association with autism-related features. We will leverage the ASD-related phenotyping data collected in the parent R01 and collect both sleep actigraphy and fNIRS data concurrently with ASD assessment visits for 50 participants in R01HD110542 Project Year 2. We will collect child actigraph data across seven continuous days and nights and calculate sleep duration (sum of nighttime and daytime sleep episodes), timing (sleep start and end time), consolidation (ratio of daytime sleep duration/nighttime sleep duration), and fragmentation (number and duration of nighttime awakenings). Caregivers will also complete a standard daily sleep diary and sleep questionnaire to assess contextual factors impacting child sleep environment. Brain activity will be measured during the study visit via fNIRS. We will evaluate the feasibility of collecting usable data from these measures in children with young children with DS and subsequently analyze how physiological dimensions are associated with early social communication and play, two dimensions relevant for early ASD detection. Results may facilitate the discovery of additional indicators of ASD risk in DS, and potentially identify mechanisms that contribute to the onset of ASD in DS in ways that can inform future treatments in this population.