B-Vitamin Intake and Biomarker Status in Relation to Cognitive Decline in Healthy Older Adults in a 4-Year Follow-Up Study

Abstract

Advancing age can be associated with an increase in cognitive dysfunction, a spectrum of disability that ranges in severity from mild cognitive impairment to dementia. Folate and the other B-vitamins involved in one-carbon metabolism are associated with cognition in ageing but the evidence is not entirely clear. The hypothesis addressed in this study was that lower dietary intake or biomarker status of folate and/or the metabolically related B-vitamins would be associated with a greater than expected rate of cognitive decline over a 4-year follow-up period in healthy older adults. Participants (aged 60-88 years; n = 155) who had been previously screened for cognitive function were reassessed four years after initial investigation using the Mini-Mental State Examination (MMSE). At the 4-year follow-up assessment when participants were aged 73.4 ± 7.1 years, mean cognitive MMSE scores had declined from 29.1 ± 1.3 at baseline to 27.5 ± 2.4 (p < 0.001), but some 27% of participants showed a greater than expected rate of cognitive decline (i.e., decrease in MMSE > 0.56 points per year). Lower vitamin B6 status, as measured using pyridoxal-5-phosphate (PLP; <43 nmol/L) was associated with a 3.5 times higher risk of accelerated cognitive decline, after adjustment for age and baseline MMSE score (OR, 3.48; 95% CI, 1.58 to 7.63; p < 0.05). Correspondingly, lower dietary intake (0.9-1.4 mg/day) of vitamin B6 was also associated with a greater rate of cognitive decline (OR, 4.22; 95% CI, 1.28-13.90; p < 0.05). No significant relationships of dietary intake or biomarker status with cognitive decline were observed for the other B-vitamins. In conclusion, lower dietary and biomarker status of vitamin B6 at baseline predicted a greater than expected rate of cognitive decline over a 4-year period in healthy older adults. Vitamin B6 may be an important protective factor in helping maintain cognitive health in ageing.

Keywords: B-vitamin biomarkers; ageing; cognition; dietary intakes; one-carbon metabolism; pyridoxal-5-phosphate (PLP); vitamin B6.

Figure 1

Study Design and flow of participants through the study. Abbreviations: FSA, Food Standards Agency; FFQ, Food Frequency Questionnaire; MMSE, Mini Mental State Examination; ¹ Failed to meet inclusion criteria at follow-up assessment n = 26; declined to participate n = 43; deceased n = 4; non contactable n = 21; participation in other research n = 6.

Figure 2

Relationship between dietary intake and biomarker status of B-vitamins at baseline (n = 148): (a) association between red blood cell folate and total folate intake; (b) association between holoTC and vitamin B12 intake; (c) association between pyridoxal-5-phosphate and vitamin B6 (d) association between EGRAC and riboflavin intake. Correlations were calculated using Pearson’s correlation coefficients (r). p < 0.05 was considered significant. HoloTC, holo-transcobalamin; PLP, Pyridoxal-5-phosphate—a measure of vitamin B6 status; EGRAC: erythrocyte glutathione reductase activation coefficient, a functional indicator of riboflavin status. The change in cognitive function score, as measured using MMSE is shown in Table 2. Over the 4-year follow-up period, a significant decline in the mean MMSE by almost 2 points was observed; the scores for each component of the MMSE (i.e., orientation, attention, recall, total verbal and language) also declined significantly, with the exception of registration. Whilst all participants had a MMSE score within the normal range at baseline (i.e., according to the inclusion criteria), 12% had a score indicative of mild cognitive impairment (MMSE range 18–24) at the time of follow-up. Overall, the average decrease in MMSE score per year was 0.42 ± 0.56; but some participants 42 (27%) had a greater than expected rate of cognitive decline (i.e., decrease in MMSE score > 0.56 points per year; [38].