High-dose vitamin D linked to better cognitive function in adults at risk of dementia

Higher daily intake of vitamin D supplements may be associated with better cognitive performance in older adults who have sleep problems and mild cognitive impairment (MCI), according to a preliminary study from Emory University.

The study included 54 adults with both sleep disturbances and MCI, a condition often considered an intermediate stage between normal age-related cognitive changes and dementia.

Researchers found that participants who reported taking at least 5,000 IU of vitamin D per day performed better on cognitive testing than those who did not take vitamin D at that level. Their scores on the Montreal Cognitive Assessment (MoCA), a widely used screening tool for memory and thinking abilities, were more than 13% higher even after researchers accounted for other factors.

Lower daily amounts of vitamin D were not associated with higher cognitive scores.

Timing may be especially important

The researchers emphasize that the findings may be particularly relevant during the early stages of cognitive decline. MCI can occur before dementia develops, potentially creating a period when interventions aimed at protecting brain health may still have an impact.

“In older adults experiencing both sleep disturbance and mild cognitive impairment, this may represent a critical window for intervention,” said Victoria Pak, the study's senior author and an associate professor at Emory University's Nell Hodgson Woodruff School of Nursing.

The researchers also noted that cognitive performance did not appear to differ depending on whether participants took vitamin D2 or vitamin D3.

Vitamin D, sleep and brain health

Vitamin D plays an important role in muscle and nerve function and is also involved in regulating sleep and circadian rhythms.

Sleep disturbances are common among people with Alzheimer's disease, and previous research has suggested a two-way relationship between poor sleep and cognitive decline. Vitamin D deficiency has also been associated with sleep problems, including insomnia and more frequent nighttime awakenings.

The Emory study is preliminary, but the researchers say it is the first to examine the relationship between vitamin D supplement intake and cognitive performance specifically in people who have both MCI and sleep disturbances.

The study was published in Sleep Medicine.

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