In elderly individuals showing early signs of dementia and experiencing sleep problems, taking high doses of vitamin D has been linked to noticeable improvements in cognitive function.

Currently, more than 7 million people in the United States suffer from dementia caused by Alzheimer’s disease. By 2050, this number is expected to rise to nearly 13 million. A recent study conducted by Emory University found that increased vitamin D intake may be associated with better cognitive performance in adults at higher risk of developing dementia.

Study Overview

The study involved 54 adults with sleep disturbances and mild cognitive impairment (MCI), which can indicate the early stages of dementia. Participants who took at least 5,000 IU of vitamin D daily showed better results on cognitive tests compared to those who did not take vitamin D. According to data published in the journal Sleep Medicine, individuals consuming 5,000 IU or more of vitamin D per day scored over 13% higher on the Montreal Cognitive Assessment (MoCA) compared to participants who did not take vitamin D, even after accounting for other factors. The MoCA is a widely used screening tool for assessing memory, thinking abilities, and dementia risk.

Lower daily doses of vitamin D were not associated with improved cognitive performance. The researchers also emphasized the importance of timely intervention, as MCI represents an intermediate stage between normal aging and dementia. In older age, when both sleep disturbances and mild cognitive impairment are present, there may be a critical window for intervention—when changes are just beginning to appear but there is still an opportunity to support brain health. Identifying accessible and modifiable factors, such as vitamin D supplementation in the early stages of cognitive decline, becomes especially important as Alzheimer’s cases continue to rise.

Additional Observations

The study also examined whether the form of vitamin D affected the results. Cognitive outcomes were similar among those taking vitamin D2 (derived from plants and mushrooms) and vitamin D3 (produced by the body through sunlight exposure and found in animal-based foods).

Vitamin D is essential for muscle and nervous system function and also plays a role in regulating sleep and circadian rhythms. Sleep problems are common in people with Alzheimer’s disease: about 50% of patients with moderate to severe forms of the illness report sleep disturbances, indicating a two-way relationship between poor sleep and cognitive decline.

Previously, vitamin D deficiency has been linked to sleep problems, including insomnia and frequent nighttime awakenings. This preliminary study is the first to specifically examine the relationship between vitamin D supplementation and cognitive function in a high-risk group experiencing both MCI and sleep disturbances.