November 08, 2012

Vitamin B12 Deficiency And Cognition: Early Studies, Part 1


Prevalence Versus Intervention:

There are two main types of study into the relationship between Vitamin B12 deficiency and cognition: those which simply evaluate the relationship between the two (Prevalence Studies) and those which determine the effects of B12 supplementation on cognition (Intervention Studies).

In this Blog post we will consider some of the early Prevalence Studies. 

"The Mind Occasionally Wanders":

Mental disturbance associated with B12 deficiency has been recognised since Thomas Addison’s first description of pernicious anaemia when he noted that, “…the mind occasionally wanders.”  Dementia was then reported in a few studies concerning Vitamin B12 in the 1950’s and there were several critical reviews into this relationship.  One of the problems identified was that the dementia did not always get better after correcting the deficiency. There could be several reasons for this of course, and in later Blog Updates we will look at studies which suggest that there is likely a "time-limited window of opportunity for intervention."

Post Mortem Studies:

Remarkably, there are very few post-mortem tissue studies of B12 and dementia. In 1982 one such study investigated the Vitamin B12 content of brains in twelve autopsy cases of elderly patients with dementia (Inada et al Int.J.Vit.Nutr.Res 1982;52:423-29).  The study showed a decrease in B12 in these brains with severe neuronal loss, myelin degeneration, brain shrinkage (atrophy) and vascular lesions in comparison with controls.  Interestingly, the researchers also studied twelve autopsy cases of vascular dementia and found a similar marked reduction in B12 content in brain tissue.

Relationship between Vitamin B12 Levels and Cognitive Scores:

In 1990 Bell et al conducted a retrospective study to examine the relationship between cognitive scores and serum Folic Acid and Vitamin B12 levels in 102 psychiatric patients aged from 60 to 100 years (Bell et al Biol Psych 1990;27:125-37).  Although their records indicated satisfactory nutritional status, correlation analyses showed that those with below average values for both folate and B12 had significantly lower cognitive scores than those who were higher in folate and/or B12.

In our next Blog update we will look at some of the early Intervention Studies concerning Vitamin B12 and Cognition.

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