Risk for Severe/Profound Intellectual Disability in Down Syndrome

Abstract Down syndrome (DS) predisposes individuals to a wide range of cognitive outcomes, with some individuals acquiring more advanced cognitive skills and others demonstrating severe or profound levels of intellectual disability (S/PID). The early origins of S/PID in individuals with DS are poorly understood, and individuals with

DS and S/PID are often underrepresented in the scientific literature. This project will address an important gap in our knowledge and establish a novel account of variability in cognitive skill acquisition in DS with an emphasis on understanding those children who demonstrate the most pronounced levels of early cognitive delay. We will

characterize early cognitive growth in young children with DS and examine the association between severe/profound early cognitive delays and behavior, biomedical factors, and molecular biosignatures known to be affected by DS, such as various inflammatory processes, elevated neurodegeneration and neuroinflammation

biomarkers, dysregulation of the growth hormone (GH)-IGF1 axis, and dysregulated metabolism. To achieve this goal, we will recruit 90 children with DS to be assessed at three data waves (Wave 1 = 12 months; Wave 2 = 24 months; Wave 3 = 36 months) and we will conduct comprehensive cognitive and broader developmental

evaluations. Blood samples will be collected concurrently with each visit and biomedical history information will be obtained. We will then model latent growth trajectories along early cognitive and other developmental domains and examine the association between growth profiles, biomedical history, molecular biosignatures, and

severe/profound degrees of early cognitive delay at Wave 3. This integrated approach to characterizing heterogeneity in cognitive delays in DS can potentially transform the nature of treatments and interventions for those individuals who are in need of the most intensive degree of lifelong community support.