The purpose of the proposed project is to test and refine a battery of cognitive measures that can be used in treatment studies focused on Down syndrome. The battery is designed to assess several key domains of the Down syndrome cognitive phenotype where gaps remain in outcome measures, including attention, executive function, learning and memory, processing speed, and social cognition, considering comorbid conditions that can potentially interfere with the development within these cognitive domains. Although a single battery for the entire lifespan of the individual with Down syndrome has obvious appeal, the investigators have focused their effort on the school-age years so that the investigators can capture a key time point in development of these cognitive domains. Moreover, new pharmaceutical treatments are transitioning from adults to the school-age population, making the need greatest for this portion of the lifespan.

However, based on preliminary research from the ongoing study with children, a need was identified to evaluate measures with young adults with DS (ages 18-39). Supplementary funding will support the expansion of the project to include young adults with DS. Results will provide empirical guidance for refining a battery and form the foundation for a larger-scale study evaluating outcome measures.

For participants 6-17 years, at least 160 children with Down syndrome will be recruited across two sites for the study, and participants will be enrolled over four (4) years. Following pre-screening and the consent visit to determine study eligibility, children will be assessed at 6 time points. The first assessment will be the baseline testing/Time 0 visit to assess IQ. At Time 1 baseline assessments for other functioning will be completed. A two-week interval will separate Time 1 and Time 2, at which time test-retest reliability assessments will be collected. Time 3 will occur three months following Time 2 to evaluate test sensitivity to change. Time 4 will occur 3 months following Time 3 and Time 5 will occur 6 months after Time 4 to assess longitudinal changes. The time interval was selected to replicate the duration of many clinical trials.

For participants 18-35 years, at least one hundred young adults aged 18-29 years with DS will be recruited across two sites to participate in the study. Adults will participate in neuropsychology assessments at 5 time points. Parents/Caregivers will complete behavioral measures at all time points. At Time 1 baseline assessments will be completed. A two-week interval (+/- 3 days) will separate Time 1 and Time 2, when test-retest reliability assessments will be collected. Time 3 will occur three months following Time 2 (+/- 2 weeks), Time 4 will occur three months following Time 3 (+/- 2 weeks), and Time 5 will occur 6 months following Time 4 (+/- 2 weeks) to evaluate sensitivity to change, Time 6 will occur 24 months following Time 1 (+/- 4 weeks), Time 7 will occur 36 months following Time 1 (+/- 4 weeks), and Time 8 will occur 48 months following Time 1 (+/- 4 weeks) to evaluate sensitivity to change. The three and six-month time intervals were selected to replicate the duration of many clinical trials. The 12-month interval was selected to provide a time interval in which natural development should occur and allow the investigators to evaluate sensitivity to change. In this study, change will occur due to natural development, while in a clinical trial, change would be expected due to treatment. The ability to detect relatively small developmentally-based change over 12 months will allow the investigators to evaluate if the measures could detect similarly small changes in trials. Once recruitment goals are met for NIH standards for 100 young adults, aged 18-29, the study team may begin recruiting adults who are 29-35, as well.