Higher vitamin D supplement intake was associated with better cognitive scores in adults with mild cognitive impairment and sleep disturbances.
More than 7 million Americans are living with Alzheimer’s dementia, and that number is projected to approach 13 million by 2050. Against that backdrop, research from Emory University suggests that higher vitamin D supplement intake is associated with better cognitive function among adults already at elevated risk of dementia.
The study included 54 adults with sleep disturbances and mild cognitive impairment (MCI), both associated with early cognitive decline. Participants who reported taking at least 5,000 IU of vitamin D each day performed better on measures of cognitive function than those who did not take vitamin D.
Early cognitive decline may offer a window
Published recently in Sleep Medicine, the study found that participants consuming at least 5,000 IU of vitamin D daily scored more than 13% higher on the Montreal Cognitive Assessment (MoCA) than participants who took none, even after researchers accounted for other factors. MoCA is a widely used screening tool that evaluates memory and thinking abilities and helps identify people at risk of cognitive impairment. Lower daily doses of vitamin D were not associated with higher cognitive scores in this study.
Timing may also matter because MCI represents an intermediate stage between typical cognitive aging and dementia.
“In older adults experiencing both sleep disturbance and mild cognitive impairment, this may represent a critical window for intervention, when cognitive changes are emerging, but opportunities to support brain health may remain,” says Victoria Pak, senior author of the study.
“Identifying accessible and modifiable factors, such as vitamin D supplement intake, during the earlier stages of cognitive decline may become increasingly important, particularly as rates of Alzheimer’s disease continue to rise,” adds Pak, associate professor at Emory University’s Nell Hodgson Woodruff School of Nursing.
Vitamin D form made no difference
Cognitive performance did not differ according to which form of vitamin D participants took. Vitamin D2 generally comes from plants or fungi, while vitamin D3 can be produced through sun exposure or obtained from animal-based foods.
Vitamin D is an essential nutrient involved in muscle and nerve function, and it also influences sleep quality and sleep-wake cycles. Sleep problems are common in Alzheimer’s disease, with 50% of people with moderate to severe disease reporting sleep disturbances, reflecting a bidirectional relationship between disrupted sleep and cognitive decline.
Vitamin D deficiency has also been associated with sleep problems such as insomnia and more frequent nighttime awakenings. According to the researchers, this preliminary study is the first to examine the relationship between vitamin D supplement intake and cognitive function specifically in a high-risk population experiencing both MCI and sleep disturbances.
Reference: “Vitamin D supplement intake is associated with better cognition in persons with sleep disturbance and mild cognitive impairment” by Sirui Zhou, Paul Sudeshna, Lynn Marie Trotti, Donald Bliwise and Victoria Pak, 10 April 2026, Sleep Medicine.
DOI: 10.1016/j.sleep.2026.108960
This study was funded by the National Institute on Aging of the National Institutes of Health, R01AG097853-01 and R61AG080606.
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