Serum 25-hydroxy vitamin D level is associated with cognitive impairment in people aged 65 years and older

Vitamin D deficiency is prevalent in the population, especially in older people. In recent years, studies have revealed an association between a low vitamin D level and cognitive decline. The present research aimed to investigate the relationship of serum 25-hydroxyvitamin D (25-OH-D) level with cognitive function in senior patients.

We recruited 299 patients aged 65 years and older. The patients were grouped based on their serum 25-OH-D levels into group A (<10.0 ng/mL), B (10.0-19.9 ng/mL), and C (≥20.0 ng/mL). Cognitive function was assessed with the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Clinical Dementia Rating (CDR) scale, and Activities of Daily Living (ADL) scale.

MMSE and MoCA scores were significantly lower in group A (26.02±3.99 and 21.56±5.59, respectively) than in group B (27.34±2.79 and 23.94±4.74, respectively) and group C (27.65±2.54 and 24.95±4.45, respectively). The proportion of patients with cognitive impairment was increased in group A (71.1%) compared to group B (55.3%) and group C (43.9%), and the difference was statistically significant (both P<0.01). Spearman's correlation analysis showed that MMSE and MoCA had a positive relationship with serum 25-OH-D level (β=0.173 and 0.243, both P<0.01) with adjustments for factors as age, sex, and education level. Stepwise regression analysis indicated that MMSE and MoCA scores were correlated with serum 25-OH-D level, age, and education level.

A lower level of 25-OH-D is common in senior patients and is associated with cognitive impairment. Patients with severe deficiency of vitamin D (serum 25-OH-D level <10 ng/mL) have lower MMSE and MoCA scores and a higher risk of cognitive dysfunction.