Cache County Study Investigators: Other investigators involved in this project include James Anthony, PhD, Erin Bigler, PhD, Ron Brookmeyer, PhD, James Burke, MD, PhD, Eric Christopher, MD, Jane Gagliardi, MD, Robert Green, MD, Michael Helms, BS, Christine Hulette, MD, Ara Khachaturian, PhD, Liz Klein, MPH, Carol Leslie, MS, Constantine Lyketsos, MD, MHS, Lawrence Mayer, MD, John Morris, MD, Ron Munger, PhD, MPH, Chiadi Onyike, MD, MHS, Truls Ostbye, MD, PhD, MPH, Ron Petersen, MD, Carl Pieper, DrPH, Kathy Piercy, PhD, Brenda Plassman, PhD, Peter Rabins, MD, Pritham Raj, MD, Russell Ray, MS, Linda Sanders, MPH, Ingmar Skoog, MD, PhD, David Steffens, MD, MHS, Martin Steinberg, MD, Marty Toohill, PhD, Leslie Toone, MS, Jeannette Townsend, MD, Lauren Warren, PhD, Heidi Wengreen, PhD, Michael Williams, MD, and Bonita Wyse, PhD. Neuropsychological testing and clinical assessment procedures were developed by Drs Welsh-Bohmer and Breitner. Dr Tschanz provided training and oversight of all field staff and reviewed all individual neuropsychological test results to render professional diagnoses. The board-certified or board-eligible geriatric psychiatrists or neurologists who examined the study members included Drs Steinberg, Breitner, Steffens, Lyketsos, Gagliardi, Raj, Christopher, and Green. Dr Williams also examined several subjects and provided expert neurologic consultation. Autopsy examinations were conducted by Dr Townsend. Ms Leslie coordinated the autopsy enrollment program. Diagnosticians at the expert consensus conferences included Drs Breitner, Burke, Lyketsos, Plassman, Steffens, Steinberg, Toohill, Tschanz, and Welsh-Bohmer.