Vitamin D and Alzheimer's disease: is there a link?

OBJECTIVE: To review the research on a possible link between Alzheimer's disease (AD) and vitamin D deficiency. DATA SOURCE: MEDLINE/PUBMED (January 1950-January 2010) and ISI Web of Science searches (January 1900-January 2010) were conducted using the key words vitamin D, Alzheimer disease, and dementia to identify pertinent studies. The Cochrane Library was searched to identify review articles along with clinicaltrials.gov to identify unpublished research. STUDY SELECTION AND DATA EXTRACTION: Vitamin D and (Alzheimer* disease or dementia) was entered into each database. Manual review of the search results identified trials that discussed an association between AD or dementia and vitamin D. Manual bibliography searches were performed to identify other pertinent articles. DATA SYNTHESIS: Vitamin D deficiency is a widespread problem among the elderly and has been associated with multiple disease states. Vitamin D deficiency has recently been linked to dementia, particularly AD, through several mechanisms. Current clinical trials discuss a possible link between low vitamin D levels and low cognitive test scores in AD patients.
CONCLUSION: The current observational studies seem to identify a link between vitamin D and dementia, particularly AD. Before this evidence can be used to make a recommendation for routine supplementation in elderly patients to prevent AD, more prospective trials with a longer follow-up period are needed to show a causality relationship.