The National Center for Health Statistics (NCHS) is pleased to offer downloadable public-use data files through the Centers for Disease Control and Prevention's (CDC) FTP file server.Users of this service have access to data sets, documentation, and questionnaires from NCHS surveys and data collection systems.he National Center for Health Statistics (NCHS) is pleased to offer downloadable public-use data files through the Centers for Disease Control and Prevention's (CDC) FTP file server.