Vitamin D supplement intake is associated with better cognition in persons with sleep disturbance and mild cognitive...

Sleep disturbances affect nearly half of individuals with mild cognitive impairment (MCI), a population at elevated risk of progressing to Alzheimer's disease (AD). Vitamin D's role in cognitive outcomes, particularly among individuals with sleep disturbance and MCI, remains unclear. This study explored associations between cognitive function and vitamin D supplement intake in individuals with MCI and sleep disturbance-a high-risk group that may be more vulnerable to progression toward AD.

This cross-sectional study included 54 participants with diagnosed or suspected mild cognitive impairment (MCI) and disturbed sleep (as determined by validated sleep questionnaires). We administered the MoCA (Montreal Cognitive Assessment) to assess cognition. Disturbed sleep was defined using the Pittsburgh Sleep Quality Index (PSQI ≥ 5) or the Epworth Sleepiness Scale (ESS ≥ 10). Vitamin D supplement intake was assessed by self-reported questionnaire. A multiple linear regression model was utilized to examine the association between vitamin D supplement intake and cognitive impairment (MoCA score), controlling for covariates of age, sex, body mass index (BMI), vitamin D type, and education.

Participants had a mean age of 67.2±8.9, a mean BMI of 29.5±7.2 kg/m², and 46% were male. Participants who took a daily dosage of 5000+ IU of vitamin D showed a marginally significant association with total MoCA score (adjusted mean (SE) = 3.78 (1.77); p = 0.039) in comparison to individuals who did not take daily vitamin D. Having a college degree was significantly associated with a higher total MoCA score (adjusted mean (SE) = 3.14 (1.38); p = 0.031. Individuals who were overweight also demonstrated higher total MoCA scores (adjusted mean (SE) = 3.59 (1.36); p = 0.013. No significant differences were found between individuals who regularly took vitamin D3 versus D2. Lower doses of Vitamin D did not significantly impact total MoCA score.

To our knowledge, this is the first study to evaluate the relationship between vitamin D supplemention and overall global cognition in individuals with both sleep disturbance and MCI. Our findings suggest that taking higher doses of daily vitamin D supplementation is associated with better overall cognitive performance in this population.