Effects of serum vitamin B12 and folate status on episodic memory performance in very old age: a population-based study.

We examined the relationship between low levels of serum vitamin B12 (< 200 pmol/L) and folic acid (< 11 nmol/L), separately or combined, and episodic memory performance in very old age. Participants with low serum vitamin values were compared with a control group matched for age and educational level. Participants (N = 250) were selected from a group of nondemented, community-dwelling persons ages 75-96. Episodic memory was tested by means of free recall and recognition of slowly and rapidly presented words. Results indicated a deterioration in both free recall and recognition as a function of serum vitamin status. However, no linear effects of vitamin levels on memory were observed, indicating that vitamin B12 and folic acid status may effect memory only among individuals at the low end of the distribution. We speculate that the vitamin-related memory deficit may reflect encoding problems, possibly due to alterations in brain metabolism.