Vitamin D linked to 13% higher cognitive scores in MCI

Vitamin D and cognitive function: what happened

A new report from Emory University linked higher vitamin D supplement intake to better cognitive scores in older adults who already had mild cognitive impairment (MCI) and sleep disturbances.

The findings were published in the journal Sleep Medicine and focus on a group considered at higher risk for dementia because both MCI and sleep problems can appear early in the course of cognitive decline.

• Source: Emory University report in Sleep Medicine (2026)
• Population studied: adults with MCI plus sleep disturbances
• Outcome: performance on the Montreal Cognitive Assessment (MoCA)

Vitamin D and cognitive function: what the evidence shows

This was a preliminary study of 54 adults with MCI and sleep disturbances that examined how reported vitamin D supplement intake related to cognitive performance.

Participants taking at least 5,000 IU of vitamin D daily scored more than 13% higher on the Montreal Cognitive Assessment (MoCA) than those taking no vitamin D, even after the researchers adjusted for other factors.

• Higher intake group: 5,000 IU/day or more, reported
• Comparison group: no vitamin D supplement reported
• Lower daily doses: not associated with improved cognitive scores in this study
• Cognitive test used: MoCA, a screening test for memory and thinking skills

Dose and type: what mattered in this study

In this study, the link to higher cognitive scores appeared only in the group taking at least 5,000 IU per day, while lower daily doses were not associated with improved cognitive scores.

The form of vitamin D did not appear to change results, with similar cognitive performance among people taking vitamin D2 and vitamin D3.

• Vitamin D2: typically obtained from plants or fungi (as described in the report)
• Vitamin D3: produced after sun exposure and can come from animal-based foods (as described in the report)

Why this matters for recovery and metabolic health context

For readers focused on recovery, the study points to a potential overlap between sleep health and brain health in people already showing early cognitive changes.

The authors note that sleep problems are common in Alzheimer’s disease, and the report cites that 50% of those with moderate to severe Alzheimer’s disease report sleep disturbances, suggesting a two-way relationship between poor sleep and cognitive decline.

• Vitamin D is described as essential for muscle and nerve function in the report
• The report also notes vitamin D plays a role in sleep quality and sleep-wake cycles
• The researchers framed MCI as an intermediate stage between normal cognitive aging and dementia

Limitations and what to watch next

These findings are preliminary and apply to a specific high-risk group: adults with both sleep disturbances and mild cognitive impairment.

The study reports an association between higher vitamin D supplement intake and better MoCA scores, which means it does not establish that vitamin D caused the improvement.

• Sample size: 54 participants
• Outcome is a screening test score (MoCA), not a diagnosis or long-term dementia outcome
• Funding: National Institute on Aging of the National Institutes of Health (R01AG097853-01 and R61AG080606)
• Senior author quote: Victoria Pak said this period may be a “critical window for intervention” when cognitive changes are emerging and modifiable factors may matter