Objectives: The aim of this cross-sectional study was to evaluate which cognitive domains are mostly affected in persons with vitamin D insufficiency or deficiency, defined as 25(OH)D < 50 nmol/l and < 25 nmol/l, respectively.
Methods: Data were collected from the Norwegian register for persons assessed for cognitive symptoms (NorCog). 580 persons aged ≥ 65 years were included. The following cognitive and neuropsychiatric tests were used: Mini Mental State Examination, Norwegian Revised Version (MMSE-NR), the Clock Drawing test, the Trail Making Test A and B, the 10-word memory test and the figure copying test from CERAD - immediate and delayed recall, The Controlled Oral Word Association Test -FAS and Boston Naming test. Neuropsychiatric symptoms were assessed by Neuropsychiatric Inventory-Questionnaire and Cornell Scale for Depression in Dementia.
Results: Vitamin D-insufficiency was found in approx. 30 % of the study cohort. After adjustment for relevant covariates, higher serum 25(OH)D levels were associated with higher score on MMSE-NR (p=0.032) and 10-word Memory Test, immediate recall (p=0.038), as well as faster execution of Trail Making Test A and B (p=0.038 and p=0.021, respectively). Other tests were not significantly associated with 25(OH)D levels.
Conclusion: Higher vitamin D levels appear to be associated with better cognition, especially in areas of executive function and mental flexibility.
Keywords: Vitamin D; dementia; executive function; neurocognitive function.