Elevated homocysteine (Hcy) levels have been associated with an increased risk of cognitive impairment and Alzheimer's disease (AD). Tissue factor pathway inhibitor (TFPI) has recently emerged as a candidate marker of endothelial damage in AD. We investigated the relationship between plasma levels of folate, vitamin B12, Hcy, and TFPI, as well as cognitive function in 321 [100 each with mild cognitive impairment (MCI) and AD, 121 normal subjects] Korean elderly (mean age 74.8 ± 7.2 years). Plasma folate and vitamin B12 concentrations were analyzed by radioimmunoassay, Hcy by the HPLC-fluorescence method, and TFPI by enzyme-linked immunosorbent assay. Plasma Hcy levels were higher in patients with AD and MCI than those in normal subjects (p < 0.001). The AD group had higher proportions of hyperhomocysteinemic (>15 μM) and folate deficient (<3.0 ng/mL) (p = 0.026) subjects. A multiple regression analysis after adjusting for covariates revealed positive relationships between plasma folate and the MMSE-KC and Boston Naming Test, and between plasma vitamin B12 and the Word List Memory Test in the AD group, but negative associations between plasma Hcy and the Word List Memory and Constructional Recall Tests and between plasma TFPI and the Boston Naming, Word List Recall, and Constructional Recall Tests. In contrast, only plasma folate level was positively associated with the MMSE-KC and Boston Naming Test in the MCI group. No associations were observed in the normal group. These results suggest that plasma folate, vitamin B12, Hcy, and TFPI are associated with cognitive function in cognitively impaired (AD and MCI) elderly and that the association was stronger in patients with AD.

BackgroundIt is possible that blood B vitamins level and cognitive function may be affected by dietary intake of these vitamins, no study however has yet been conducted on relationships between B vitamins intake and cognitive function among elderly population in Korea. This study examined the relationship between B vitamins intake and cognitive function among elderly in South Korea.MethodsParticipants consisted of 100 adults with mild cognitive impairment (MCI), 100 with Alzheimer’s disease (AD), and 121 normal subjects. Dietary intake data that included the use of dietary supplements were obtained using a 24-hour recall method by well-trained interviewers. Plasma folate and vitamin B12 concentrations were analyzed by radioimmunoassay, and homocysteine (Hcy) was assessed by a high performance liquid chromatography-fluorescence method.ResultsPlasma levels of folate and vitamin B12 were positively correlated with B vitamins intake; and plasma Hcy was negatively correlated with total intake of vitamin B2, vitamin B6, vitamin B12 and folate. In the AD group, a multiple regression analysis after adjusting for covariates revealed positive relationships between vitamin B2 intake and test scores for the MMSE-KC, Boston Naming, Word Fluency, Word List Memory and Constructional Recall Tests; and between vitamin B6 intake and the MMSE-KC, Boston Naming, Word Fluency, Word List Memory, Word List Recognition, Constructional Recall and Constructional Praxis Tests. Positive associations were observed between vitamin B12 intake and the MMSE-KC, Boston Naming, Constructional Recall and Constructional Praxis Tests, and between folate intake and the Constructional Recall Test. In the MCI group, vitamin B2 intake was positively associated with the MMSE-KC and Boston Naming Test, vitamin B6 intake was positively associated with the Boston Naming Test, and folate intake was positively associated with the MMSE-KC and Word List Memory test. No associations were observed in the normal group.ConclusionThese results suggested that total B vitamins intake is associated with cognitive function in cognitively impaired AD and MCI elderly, and the association is stronger in AD patients.

This study examined the relationship among plasma homocysteine, folate, and vitamin B12 levels and neurocognitive function in 118 community-dwelling elderly subjects (mean age, 75.1 ± 6.7 years). The Mini-Mental State Examination (MMSE-KC) was used to screen and assess neurocognitive function in the participants. Dietary intake data including the use of dietary supplements were obtained using the 24-hour recall method by well-trained interviewers. Plasma folate and vitamin B12 concentrations were analyzed by radioimmunoassay, and homocysteine was assessed by a high performance liquid chromatography-fluorescence method. The proportions of participants with suboptimal levels of plasma folate (＜ 3 ng/mL), vitamin B12 (＜ 221 pmol/mL), and homocysteine ( ＞ 15 μmol/L) were 16.1%, 5.9%, and 21.2%, respectively. A multiple regression analysis showed that plasma homocysteine was negatively associated with plasma folate and vitamin B12 levels. The MMSE-KC test scores were significantly associated with plasma homocysteine and folate, but not with vitamin B12, after adjusting for age, gender, body mass index, living with spouse, education, current smoking, energy intake, and chronic diseases such as hypertension, diabetes, thyroid disease, dyslipidemia, stroke, and cardiovascular disease. A general linear model adjusted for covariates revealed that MMSE-KC test scores increased from the lowest to the highest quartiles of vitamin B1, vitamin B2, vitamin B6, vitamin B12, and vitamin C intake (p for trend = 0.012, 0.039, 0.014, 0.046, 0.026, respectively). These results indicate that the problem of folate inadequacy and hyperhomocysteinemia are highly prevalent among community-dwelling elderly people and that dietary intake of the B vitamins and vitamin C is positively associated with cognitive function scores. (Korean J Nutr 2011; 44(6): 498 ~ 506)

This study investigated the relationship of cognitive function with plasma homocysteine (Hcy), folate, vitamin B12 levels and nutrient intake. A total of 321 subjects, including 121 normal subjects, 100 each from mild cognitive impairment (MCI) and Alzheimerˈs disease (AD) patients participated in this study (age 60 yrs and over). Diagnostic assessments were administered using the Korean version of Consortium to Establish a Registry for Alzheimerˈs Disease. Dietary intake was assessed using 24‐hour recall. Mean plasma Hcy level was higher in AD and MCI compared to normal subjects. AD group also had higher proportion of hyperhomocysteinemia and folate deficiency. Plasma Hcy level was negatively correlated with plasma folate and vitamin B12 levels, total intake of vitamin B2, vitamin B6, folate, vitamin B12, vitamin C and vitamin E. Multiple regression analysis with covariates revealed that plasma Hcy level was negatively, whereas plasma folate level, total intake of vitamin B2, vitamin B6, folate, vitamin C, vitamin E and beta‐carotene were positively associated with cognitive function. The results suggest that plasma Hcy, B vitamins and antioxidants intake are associated with cognitive function, and plasma Hcy level is negatively correlated with B vitaminsˈ nutritional status and antioxidants intake.This work was supported by the Brain Korea 21 project.