Further evidence on the effects of vitamin B-12 and folate levels on episodic memory functioning: A population-based study of healthy very old adults

Background: The relationship between vitamin status and cognitive functioni ng has been addressed in several recent studies with inconclusive results. The purpose of this study was to examine separate and combined effects of s erum vitamin B-12 and folic acid on episodic memory functioning in very old age. Methods: Four study groups were selected from a population-based sample of healthy very old adults (90-101 years of age): normal B-12/normal folic aci d, low B-12/ normal folic acid, normal B-12/low folic acid and low B-12/low folic acid. Cutoff levels were set at 180 pmol/L for vitamin B-12 and at 1 3 nmol/L for folic acid. Subjects completed two episodic recall tasks (obje cts and words) and two episodic recognition tasks (faces and words). Results: Neither vitamin affected recognition or primary memory. Most inter esting, although B-12 was unrelated to recall performance, subjects with lo w folic acid levels showed impairment in both word recall and object recall . Conclusions: These results replicate and extend previous findings that foli c acid may be more critical than B-12 to memory functioning in late life. T he selective effects of folic acid on episodic recall were discussed in ter ms of encoding and retrieval mechanisms, as well as in relation to brain pr otein synthesis. (C) 1999 Society of Biological Psychiatry.