How Is Vitamin D Connected to Cognitive Impairment?

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Vitamin D levels in post-mortem brain tissue were linked with cognitive function, an autopsy study showed.

Higher concentrations of 25(OH)D3 — the main form of vitamin D assessed in the study — in four areas of the brain were linked to 25% to 33% lower odds of dementia or mild cognitive impairment, according to Sarah Booth, PhD, of Tufts University in Boston, and colleagues.

MedPage Today’s recent article entitled “Brain Vitamin D Tied to Cognitive Function” explains that brain concentrations of vitamin D were not associated with any neuropathology or biomarker outcome, Booth and her co-authors reported in Alzheimer’s & Dementia.

Connections between vitamin D and cognition have been looked at before with mixed results, noted Claire Sexton, DPhil, senior director of scientific programs and outreach at the Alzheimer’s Association in Chicago, in an email to MedPage Today. “Some studies found a connection; some did not.”

While “an interesting possible connection,” Sexton observed, “this study, because it is an observational study and not an intervention, cannot establish that the vitamin D levels cause the lower risk, only that there is a connection to lower risk. More research is needed to answer those questions.”

“Finding an association between vitamin levels and reduced risk is not the same as endorsing supplementation,” Sexton pointed out. “Previous clinical trials of vitamin D supplementation to reduce dementia risk found mixed and varying results and had side effects. It is not recommended to start vitamin D supplementation to reduce dementia risk.”

The study wanted to look at brain concentrations of vitamin D and see if associations with cognitive measures and neuropathological outcomes existed.

“Many studies have implicated dietary or nutritional factors in cognitive performance or function in older adults, including many studies of vitamin D, but all of them are based on either dietary intakes or blood measures of vitamin D,” said coauthor M. Kyla Shea, PhD, also of Tufts, in a statement. “We wanted to know if vitamin D is even present in the brain, and if it is, how those concentrations are linked to cognitive decline.”

Global Alzheimer’s pathology included counts of neuritic plaques, diffuse plaques and neurofibrillary tangles. Macroscopic and microscopic cerebral infarctions were identified as were Lewy bodies.

Cognitive evaluations were performed every year. At their last clinic visit, 40% of participants were diagnosed with dementia, 24% had mild cognitive impairment and 36% had no cognitive impairment.

Reference: MedPage Today (Dec. 8, 2022) “Brain Vitamin D Tied to Cognitive Function”