1. Department of Epidemiology Boston University School of Public Health Boston Massachusetts USA
2. Down Syndrome Program, Division of Medical Genetics Massachusetts General Hospital Boston Massachusetts USA
3. Department of Pediatrics Harvard Medical School Boston Massachusetts USA
4. Sant Pau Memory Unit, Department of Neurology Hospital de la Santa Creu Sant Pau, Biomedical Research Institute Sant Pau Barcelona Spain
5. Barcelona Down Medical Center Fundació Catalana Síndrome de Down Barcelona Spain
6. Instituto de Investigación ‐ Hospital de la Santa Cruz y San Pablo Centro de Investigación Biomédica en Red en Enfermedades Neurodegenerativas (CIBERNED) Madrid Spain