Thomas J. Littlejohns,

Supplemental data at Neurology.org Vitamin D and the risk of dementia and Alzheimer disease Objective: To determine whether low vitamin D concentrations are associated with an increased risk of incident all-cause dementia and Alzheimer disease. Methods: One thousand six hundred fifty-eight elderly ambulatory adults free from dementia, cardiovascular disease, and stroke who participated in the US population–based Cardiovascular Health Study between 1992–1993 and 1999 were included. Serum 25-hydroxyvitamin D (25 (OH)D) concentrations were determined by liquid chromatography-tandem mass spectrometry from blood samples collected in 1992–1993. Incident all-cause dementia and Alzheimer disease status were assessed during follow-up using National Institute of Neurological and Communica-tive Disorders and Stroke/Alzheimer’s Disease and Related Disorders Association criteria. Results: During a mean follow-up of 5.6 years, 171 participants developed all-cause dementia