Biostatistics and Data Management Core Abstract The Biostatistics and Data Management (BDM) Core facilitates research and collaboration with ABC-DS investigators by providing data management, epidemiological, analytic design and statistical support, and by creating an infrastructure for data sharing with the research community to further the understanding of Alzheimer’s Disease and Down syndrome. BDM Core personnel, lead by Drs. Tudorascu (statistics) and Andrews (data management) will support the ABC-DS Cores leaders and investigators in fulfilling the specific aims of Research Projects 1, 2 and 3 by establishing a secure, centralized online data management system, implementing a protocol to ensure the integration and documentation of clinical, neuroimaging, omics, genetic and neuropathology data and providing high-level statistical support, with expertise required to test each stated hypothesis in this project. These functions will be carried out through a multidisciplinary team of Biostatistics Methodology Groups (BMGs): statisticians, epidemiologists, and data management experts organized into groups, each with specific expertise and unique skills that can be used across several Projects and Cores. The Specific Aims that will be implemented using this organizational structure are as follows: Aim 1: Complete the transition to a unified relational database and project management system by harmonizing and integrating evaluation data across all Performance sites, incorporating the new, unified evaluation protocol, and providing functionality for scheduling and documenting all study procedures and integrating key data elements from the Clinical, Neuropathology, Omics, ADDORE and Neuroimaging Core; Aim 2: Create a set of analytic data files containing all original and derived data elements from all sources necessary for the statistical analysis required to test the hypotheses of each Research Project in this proposal, as well as create data sets meeting specifications for any secondary and ad hoc analyses planned during the conduct of this research; Aim 3: Lead the statistical data analyses, collaborate in report preparation for all Cores and Research Projects, and provide expertise on design and methodological aspects of statistical analyses for ABC-DS Research Projects; Aim 4: Develop and implement appropriate statistical models for longitudinal analyses of derived biomarkers from all modalities in order to make inferences with respect to impact at each stage of the development of AD in our cohort of adults with DS; Aim 5: Facilitate sharing of ABC-DS data through the Laboratory of Neuroimaging (LONI), serve as a methodological resource for researchers within and outside of ABC-DS interested in using the ABC-DS database for analyses, and provide documentation and ensure reproducibility of published ABC- DS research.