December 14, 2012

B12 Deficiency and Alzheimers Disease

Is it,... or isn't it?

We have seen in earlier Blogs how Vitamin B12 deficiency seems to be very closely related to Alzheimer's Disease (AD).

However, one of the key criticisms of these early studies was whether the B12 deficiency was truly associated with AD.  Might it instead reflect the chance occurrence of two disorders that become increasingly common as we age?

Familial Alzheimer's Disease:

The main difficulty with AD is that, strictly speaking, it cannot be officially diagnosed before a post mortem.

It is only at post mortem that the characteristic neurofibrillary tangles and amyloid plaques are seen (see Earlier Blog updates).

Prior to post mortem, the best we can say is that an individual has either "possible" or "probable" AD based on their clinical signs and symptoms.

For this reason, it was not clear whether early reports of B12 deficiency in relation to AD related to the disease itself or not. And, after all (argued researchers) both disorders are increasingly common with increasing age!

One way to resolve this was to look at members of families with inherited disorders which result in DEFINITE AD.

One such study was conducted in the mid 1990s (Age Ageing (1994):23(4) 334-7).  Interestingly patients in this family, with an inherited disorder of amyloid resulting in AD, did indeed have lower blood levels of Vitamin B12.

Oxford Project to Investigate Memory and Ageing (OPTIMA):

Robust confirmation came from the Oxford University OPTIMA project (Arch Neurol 1998: 55(11):1449-55).

This large ongoing project not only collected blood samples, but also brain samples from contributing individuals.

Remarkably, those with post mortem histopathological confirmation of AD had lower Vitamin B12 values than healthy controls.  Other studies have since confirmed this.

Without doubt, patients with AD tend to have lower vitamin B12 levels than age matched healthy control subjects.

 

We will look at the significance of this in later Blogs.

 

 

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