Vitamin B12 status and rate of brain volume loss in community-dwelling elderly
Vogiatzoglou A, Refsum H, Johnston C, Smith SM, Bradley KM, de Jager C, et al.;
Commented by , 31 Oct 2008
Aim of the study
To investigate the relationship between markers of vitamin B12 status and brain volume loss per year over a 5-year period in an elderly population.
Methods
Prospective study of 107 community-dwelling volunteers aged 61 to 87 (mean 73.2) without cognitive impairment at enrollment using a CAMCOG score > 80 and a MMSE score > 24. Blood level at baseline for plasma vitamin B12, transcobalamin (TC) saturation, holotrascobalamin (holoTC), methylmalonic acid (MMS), total homocysteine (tHcy), serum folate. Yearly assessments by clinical examination, MRI scans, cognitive tests.
Results
The decrease of whole brain volume was greater among the volunteers with lower levels of vitamin B12 and holoTC, and higher tHcy and MMA at baseline. None had vitamin B12 deficiency defined as plasma level < 150 pmol/L. Linear regression analysis showed that the association with vitamin B12 and holoTC remained significant after adjustment for age, sex, creatinine, education, initial brain volume, cognitive tests scores, systolic blood pressure, ApoE4 genotype, tHcy and folate levels. Similar findings using logistic regression analysis.
Professor Gauthier's comments
The authors should be congratulated for running a useful study with a small number of volunteers over 5 years. Their findings are significant: the authors suggest that low vitamin B12 status be further investigated as a modifiable cause of brain atrophy and of likely subsequent cognitive impairment in the elderly.
The Canadian Practice Guidelines for the Diagnosis and Management of Dementia recently added serum B12 levels to the list of laboratory investigations that should be done in all older adults suspected of cognitive impairment or dementia, and low levels should be treated with oral or parenteral B12 supplementation, even in the absence of pernicious anemia (ref. 1).
The evidence from this observational study and the body of literature on vitamin B12 is such that memory clinics interested in primary and secondary prevention of cognitive decline and dementia should routinely measure B12 blood levels and suggest long term B12 supplementation even with blood levels in lower range of normal, at least until a prospective randomized intervention study proves otherwise.
References
1. Feldman HH, Jacova C, Robillard A, Garcia A, Chow T, Borrie M, et al. Diagnosis and treatment of dementia: 2. Diagnosis. CMAJ 2008; 178 (7); 825-386. (Free full text article)