B-vitamin status and cognitive function in older people

Abstract

Background: Dementia is a growing public health concern; there are currently 750 000 people living with the disease in the UK. By 2025 this number is expected to rise to over a million with costs estimated at over £20 billion per annum (Alzheimer's society, 2010). Diet is considered to play an important role in the development of cognitive impairment with recent research now identifying a role for B vitamins (Kado et al., 2005). The aim of this observational study was to investigate the association between B-vitamin status (in particular, vitamin B12 and folate) and cognitive function in older people. Methods: This study was conducted as part of a larger ongoing observational study of older Irish adults; Trinity Ulster Department of Agriculture (TUDA) study. Patients who were not born in the Republic of Ireland or Northern Ireland and those with severe dementia were excluded. A non-fasting blood sample (50 mL) was collected; routine clinical markers of health were measured as well as B vitamin status [serum folate, red cell folate (RCF), serum B12 and holotranscobalamin (holoTC)]. Cognitive function was measured using various cognitive performance tests including Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Depression and anxiety were measured using the Centre of Epidemiological Studies Depression (CES-D) scale and Hospital Anxiety and Depression (HAD) scale respectively to adjust for these possible confounders of cognitive performance. Data were analysed statistically using independent t tests, chi-squared tests and Pearsons correlations. Ethical approval was granted for the recruitment of patients over the age of 60 years from outpatient clinics and GP practices within two health trusts in Northern Ireland. Results: The cohort (n = 100) was split for analysis purposes into those aged 60–69 years (n = 70) and those aged ≥70 years (n = 30). There were no significant differences between the groups in terms of cognitive scores or B vitamin status (some of the results are shown in Table 1). No significant associations were found between B vitamin status and cognitive scores in the group as a whole or in the younger age group. However, in those aged 70 years or older, folate status (RCF concentrations) was found to be significantly associated with MMSE scores (r = 0.370, P = 0.048) while the association between RCF and RBANS was approaching significance (r = 0.358, P = 0.057) in those aged 70 or older. No associations were found between vitamin B12 and cognitive scores in either of the age sub-groups. Table 1. Differences between those aged 60–69 years and those aged ≥70 years in terms of cognitive scores & B vitamin status Aged 60–69 years Aged ≥70 years P value Mean (SD) Mean (SD) RBANS 86.4 (12.8) 82.5 (14.1) 0.169 MMSE 27.5 (2.7) 27.5 (3.2) 0.822 RCF (nM) 1092.2 (96.9) 1099.0 (96.0) 0.737 Discussion: The results are in line with the current literature (Tettamanti et al., 2006). Some observational data have also found associations between vitamin B12 and cognitive impairment; however, this was not the case with the present study. These findings may suggest a possible role for folate (but not B12) in certain types of dementia, such as Alzheimer's disease, as status was not associated with FAB which is used mainly in the diagnosis of frontotemporal dementia. Conclusion: Future research is warranted to confirm these associations in larger cohort trials involving two time points which will pave the way for randomised controlled trials to examine cause-and-effect relationships between B-vitamin status and cognitive performance.