Vitamin B12, B6, or Folate and Cognitive Function in Community-Dwelling Older Adults: A Systematic Review and Meta-Analysis.

BACKGROUND: Previous studies have indicated that B vitamin deficiencies are an essential cause of neurological pathology. There is a need to provide evidence of the benefit of B vitamins for the prevention of cognitive decline in community-dwelling older adults. OBJECTIVE: To examine the association between intake and plasma levels of vitamins B12, B6, and folate and cognitive function in older populations through a systematic review and meta-analysis. METHODS: Medline (PubMed), EMBASE, and Cochrane databases were used to search the literature though August 8, 2019. We included observational population-based studies evaluating the association between concentrations or intake levels of vitamins B6, B12, or folate and cognition in older adults aged ≥45 years. The quality of all studies was assessed by the modified Newcastle-Ottawa Scale. Odds ratios (ORs) and hazard ratios (HRs) were analyzed by the random-effects model. Sensitivity analyses were conducted by excluding the studies with significant heterogeneity. RESULTS: Twenty-one observational studies with sample sizes ranging from 155-7030 were included in the meta-analysis. Higher levels of vitamin B12 (OR = 0.77, 95% CI = 0.61-0.97) and folate concentration (OR = 0.68, 95% CI = 0.51-0.90) were associated with better cognition in cross-sectional studies, but not in sensitivity analyses or prospective studies. High vitamin B6 concentrations showed no significant benefit on cognition and dementia risk. Prospective studies did not provide substantial evidence for the relationship. CONCLUSION: The results from our meta-analysis suggest that vitamins B12, B6, and folate may not be modifiable risk factors for slowing cognitive decline among community-dwelling older individuals.