The influence of serum vitamin B12 and folate status on cognitive functioning in very old age.

This study examined the relationship between low levels of serum vitamin B12 and folic acid (FA) and cognitive functioning in very old age. The four subsamples of non-demented persons aged 75-96 years - normal B12/normal FA; low B12/normal FA; normal B12/low FA; and low B12/low FA, were matched for age and education. A battery of cognitive tests was administered including Clock Tests, Block Design, Trail Making Tests (TMT), Digit Span, and tests of verbal fluency. Subjects with low levels of vitamins showed deficits in Block Design, TMT-B, Digit Span Backward, and letter fluency, but not in the remaining tests. In general, the effects of FA exceeded those of B12. This pattern of results was interpreted to mean that elderly persons with low vitamin levels have difficulty when fast and accurate processing of novel information is required, but are quite efficient in utilizing pre-existing knowledge structures.