Among adults with both sleep disturbances and mild cognitive impairment, those who reported taking at least 5,000 IU of vitamin D daily had higher cognitive scores than participants who did not take vitamin D supplements at that level, according to preliminary research from Emory University.
The difference in cognitive scores
The study included 54 adults with sleep disturbances and mild cognitive impairment, or MCI. MCI is an intermediate stage between normal cognitive aging and dementia.
Participants who reported taking at least 5,000 IU of vitamin D each day scored more than 13% higher on the Montreal Cognitive Assessment, or MoCA, than those who did not. The difference remained after accounting for other factors.
The MoCA is a screening tool used to assess memory and thinking skills and to identify the risk of developing dementia.
The association was specific to the higher daily intake examined in the study. Lower doses of vitamin D were not associated with higher cognitive scores.
The findings do not establish that vitamin D supplements improve cognitive function. The study examined the relationship between reported vitamin D supplement intake and cognitive performance in this group.
Why the timing of cognitive changes matters
The researchers focused on people who had both sleep disturbances and MCI, two features associated with early dementia.
Victoria Pak, the study’s senior author, said this combination may represent a period when cognitive changes are beginning while there are still opportunities to support brain health.
The study therefore examined vitamin D intake during an early stage of cognitive decline rather than among people with established dementia.
Pak, an associate professor at Emory University’s Nell Hodgson Woodruff School of Nursing, also described vitamin D supplement intake as an accessible and potentially modifiable factor that could be examined during earlier stages of cognitive decline.
The type of vitamin D did not make a difference
The study also compared cognitive performance according to the form of vitamin D participants reported taking.
There was no difference in cognitive performance based on whether the vitamin D was D2 or D3. Vitamin D2 is typically derived from plants or fungi, while D3 is produced after sun exposure or obtained from animal-based foods.
The results therefore did not identify one of these two forms as being associated with better cognitive performance in the study group.
Vitamin D, sleep and cognition
Vitamin D is an essential nutrient involved in muscle and nerve function. It also influences sleep quality and sleep-wake cycles.
Sleep disturbances are common among people with moderate to severe Alzheimer’s disease, with 50% reported to experience them. Vitamin D deficiency has also been implicated in sleep problems, including insomnia and more nighttime awakenings.
Against that background, the Emory study examined whether vitamin D supplement intake was related to cognitive function in adults who already had both sleep disturbances and MCI.
The researchers described the work as a preliminary study and said it was the first to assess this relationship in a population with both conditions.
The study was published in Sleep Medicine.
