Vitamin B12 levels could be predictive of Parkinson’s disease dementia

Cognitive impairment, in particular dementia, is one of the most feared non-motor features of Parkinson’s disease (PD).1  Lower levels of vitamin B12 have been reported in PD patients with cognitive impairment. However, the value of vitamin B12 at PD diagnosis as a predictor for dementia is unknown.2

A retrospective study recently published in Parkinsonism & Related Disorders investigated whether serum vitamin B12 levels at PD diagnosis was associated with risk of dementia. Clinical data collected as part of the Rochester Epidemiology Project was used to identify the individuals with clinically diagnosed PD between January 1, 1991, and December 31, 2010. Researchers identified 25 patients with clinically diagnosed PD who did not have dementia at the time of diagnosis and whose data included serum vitamin B12 levels within one year prior or 90 days after the diagnosis of PD. The median age at PD diagnosis was 74.0 years (55–88). Among the 25 patients included, 15 (60%) were later diagnosed with dementia at a median age of 79.4 years (71.6–92.3).3

In an interview with VJDementia, Rodolfo Savica, MD, PhD and Stuart McCarter, MD, from Mayo Clinic, Rochester, MN, discuss the rationale of this study, the key findings and the potential impact on clinical practice. This interview was recorded during an online conference call with The Video Journal of Dementia (VJDementia).

Results showed that levels of vitamin B12 at PD diagnosis in patients who did not develop dementia were higher than in those who developed dementia (648.5 ng/L vs 452 ng/L, p < 0.05). Additionally, the vitamin B12 cutoff value of <587 ng/L was 87% sensitive and 70% specific (AUC 0.79, 95% CI 0.60–0.98) at distinguishing patients with dementia. The researchers further observed that for every 100 ng/L increase in vitamin B12 level, there was a decrease in dementia risk (hazard ratio 0.31, 95% CI 0.44–0.95).3

In the interview, Dr McCarter highlights that ‘this is a small study that helps provide some of that prognostic information for patients. I think it gives us, as clinicians, something exciting to look into in the future as to how we may help build on this or if there is anything we can do to modulate this effect that may help patients even more’.

Overall, these findings suggest that higher serum vitamin B12 levels at PD diagnosis correlate with a lower future dementia risk. However, further evaluation of vitamin B12 status in PD is needed, and clinical trials investigating interventional B vitamin supplements should be considered. Dr Savica comments that ‘we need to look more carefully in a larger prospective study’.

Written by Marta Palhas


  1. Barker R, Williams-Gray C. Mild Cognitive Impairment and Parkinson’s Disease – Something to Remember. J Parkinsons Dis. 2015;4(4):651-656.
  2. 4. Luthra N, Marcus A, Hills N, Christine C. Vitamin B12 measurements across neurodegenerative disorders. J Clin Mov Disord. 2020;7(1).
  3. McCarter S, Stang C, Turcano P et al. Higher vitamin B12 level at Parkinson’s disease diagnosis is associated with lower risk of future dementia. Parkinsonism Relat Disord. 2020 Mar;73:19-22.