Brain vitamin D forms, cognitive decline, and neuropathology in community-dwelling older adults.

INTRODUCTION: Vitamin D purportedly protects against cognitive decline and dementia based on observational data using circulating 25-hydroxyvitamin D (25(OH)D). Little is known about vitamin D in the human brain and the association with dementia or neuropathology. METHODS: Decedents of the Rush Memory and Aging Project (n = 290) had vitamin D concentrations measured in four brain regions. Associations with cognitive and neuropathological outcomes were estimated using linear and logistic regression. RESULTS: The main form of vitamin D in all brain regions measured was 25(OH)D3 . Higher brain 25(OH)D3 concentrations were associated with a 25% to 33% lower odds of dementia or mild cognitive impairment (MCI) at the last visit before death (all P ≤ .031). However, brain 25(OH)D concentrations were not associated with any post-mortem neuropathology outcome studied. DISCUSSION: Higher brain 25(OH)D3 concentrations were associated with better cognitive function prior to death. Additional research is needed to clarify the specific mechanisms underlying this potentially protective relationship.