Higher vitamin B12 level at Parkinson's disease diagnosis is associated with lower risk of future dementia

Introduction: To determine whether vitamin B12 level at Parkinson's disease (PD) diagnosis predicts time to develop dementia. Methods: We utilized a population-based cohort of Parkinsonism patients to examine the relationship between serum vitamin B12 at the time of PD diagnosis and dementia risk. Receiver operating curves were calculated for vitamin B12 cutoffs maximizing sensitivity and specificity for determining who developed dementia. Time from Parkinsonism diagnosis to dementia, death, or censoring was calculated utilizing Kaplan-Meier analysis and Cox-proportional hazard models. Results: PD patients who did not develop dementia had higher baseline levels of vitamin B12 at PD diagnosis (648.5 ng/L vs 452 ng/L, p < 0.05) than those who developed dementia. Dementia risk was significantly lower in the 3rd tertile compared with 2nd tertile and trended towards significance compared to the 1st tertile. Each 100 unit increase in vitamin B12 level had a hazard ratio of 0.31 (95% CI 0.44–0.95) for future dementia (p < 0.05). Vitamin B12 cutoff of <587 ng/L was 87% sensitive and 70% specific (AUC 0.79, 95% CI 0.60–0.98) distinguishing patients with dementia. PD patients with vitamin B12 levels <587 ng/L were 5.4 times more likely to develop dementia, with 50% having dementia within 5 years of PD diagnosis compared with 11% in those with a vitamin B12 level of ≥587 ng/L (p < 0.05). Conclusion: Higher levels of serum vitamin B12 at PD diagnosis correlate with lower risk of future dementia. The role of vitamin B12 in the development of dementia among PD patients deserves further evaluation.