Vitamin D as a possible biomarker of mild cognitive impairment in parkinsonians

Mild Cognitive Impairment in Parkinson's Disease (PD-MCI) is a transitional state between normal cognition and dementia. Cross-sectional studies revealed that low Vitamin D levels were associated with worse performance on cognitive tests in Parkinson's Disease. The present longitudinal study aimed to examine the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels at baseline and possible development of PD-MCI at 24 and 48 months.

Sixty untreated, de novo PD patients underwent clinical and cognitive evaluations and measurement of serum 25(OH)D at baseline assessment (T0). After 24 (T1) and 48 months (T2), cognitive status (presence or absence of PD-MCI) of PD patients were re-evaluated.

Vitamin D insufficiency occurred in 93.3% at T0. At T1, significant differences among patients with PD-MCI at both baseline and follow-up, patients with PD-MCI at follow-up and patients who never developed PD-MCI were found on age, age at onset of PD, and education; no significant difference was found on vitamin D levels at T0. A binary logistic regression analysis showed that a lower level of 25(OH)D at T0 (B= -0.158, Wald= 5.280, p = 0.022, Exp (B)=0.854; CI 95%: 0.746-0.977) and lower education (B= -0.214, Wald= 3.859, p = 0.049, Exp (B)=0.807; CI 95%: 0652-1.000) were predictors of PD-MCI occurrence at T2.

Our results demonstrated that a lower level of 25(OH)D is conceivable as a biomarker of development of PD-MCI throughout the disease. Early diagnosis of Vitamin D insufficiency and its management might be useful to prevent cognitive decline in PD patients.