What is the fine-grained topic of the following text: In seniors with a serum vitamin B-12 concentration <148 pmol/L or a plasma methylmalonic acid concentration > or =210 nmol/L, the presence compared with the absence of detectable circulating unmetabolized folic acid was related to lower cognitive test scores and lower mean cell volume. Only return the topic.
The relationship between unmetabolized folic acid presence and cognitive function in seniors with certain B-12 and methylmalonic acid concentrations.