Vitamin B12 deficiency in dementia and cognitive impairment: the effects of treatment on neuropsychological function.

Abstract

Vitamin B12 assay is part of the routine investigation of dementia, although few studies have investigated the effects of treatment on cognition. We examined the effects of B12 treatment on neuropsychological function and disease progression in patients presenting with dementia or cognitive impairment. From 1432 patients who were assessed at the Bristol Memory Disorders Clinic, 125 patients with low serum B12 were identified. Sixty-six patients presenting with dementia, and 22 with cognitive impairment were seen for a second assessment after treatment. Changes in neuropsychological test scores were compared with those of patients with normal serum B12, matched by age and diagnosis. The majority of patients with low serum B12 had normal Hb and MCV values. We found no cases of reversible B12 deficiency dementia. The B12 treatment patients who presented with dementia showed no significant improvement, and no less deterioration, in their neuropsychological function than their matched group. However, a treatment effect was demonstrated among the patients presenting with cognitive impairment. These improved significantly compared to matched patients on the verbal fluency test (p<0.01). All patients with cognitive impairment should be investigated for B12 deficiency. Vitamin B12 treatment may improve frontal lobe and language function in patients with cognitive impairment, but rarely reverses dementia.