Influences of Vitamin B12 Supplementation on Cognition and Homocysteine in Patients with Vitamin B12 Deficiency and Cognitive Impairment

Vitamin B₁₂ deficiency is associated with cognitive impairment, hyperhomocysteinemia, and hippocampal atrophy. However, the recovery of cognition with vitamin B₁₂ supplementation remains controversial. Of the 1716 patients who visited our outpatient clinic for dementia, 83 had vitamin B₁₂ deficiency. Among these, 39 patients (mean age, 80.1 ± 8.2 years) had undergone Mini-Mental State Examination (MMSE) and laboratory tests for vitamin B₁₂, homocysteine (Hcy), and folic acid levels. The hippocampal volume was estimated using the z-score of the MRI-voxel-based specific regional analysis system for Alzheimer’s disease. This is multi-center, open-label, single-arm study. All the 39 patients were administered vitamin B₁₂ and underwent reassessment to measure the retested for MMSE and Hcy after 21−133 days (median = 56 days, interquartile range (IQR) = 43–79 days). After vitamin B₁₂ supplementation, the mean MMSE score improved significantly from 20.5 ± 6.4 to 22.9 ± 5.5 (p < 0.001). Hcy level decreased significantly from 22.9 ± 16.9 nmol/mL to 11.5 ± 3.9 nmol/mL (p < 0.001). Significant correlation was detected between the extent of change in MMSE scores and baseline Hcy values. The degree of MMSE score was not correlated with hippocampal atrophy assessed by the z-score. While several other factors should be considered, vitamin B₁₂ supplementation resulted in improved cognitive function, at least in the short term, in patients with vitamin B₁₂ deficiency.