Background

Normal and subnormal serum levels of vitamin B12 and/or folate do not exclude functional deficiency, and elderly people are specifically exposed to deficiency owing to impaired nutrition, malabsorption, accompanying diseases and current medication. Several studies report that low levels of vitamin B12 are more common in people with Alzheimer’s disease (AD) than in non-demented people. Low levels of folate are also correlated with other types of dementia. Current studies suggest that low levels of vitamin B12 as well as folate may be part of the aetiology in AD. A functional deficiency of vitamin B12/folate may be present despite serum levels within reference limits. The amino acid homocysteine (Hcy) is a sensitive but non-specific marker of deficiency of vitamin B12 and folate and appears to have the strongest association with cognitive function. The association between Hcy levels and cognitive function is also stronger than that of the levels of vitamin B12/folate. The clinical manifestations of vitamin B12/folate deficiency are non-specific, but when they are connected with laboratory findings adequate investigation should be performed. A generous attitude to treatment with vitamin B12/folate is advocated, combined with a compulsory evaluation of treatment effect. Clinical regress of neuropsychiatric symptoms by cobalamin and folate therapy is dependent on the duration and severity of symptoms, but on a group level, not necessarily in individual patients