Association of Vitamin B Status with Risk of Dementia in Cohort Studies: A Systematic Review and Meta-Analysis



      To examine the association between B vitamins status and the risk of dementia in older adults through a systematic review and meta-analysis of cohort studies.


      Systematic review and meta-analysis.

      Setting and participants

      Older adults aged ≥60 years from community, nursing home, institution, or hospital.


      PubMed, Cochrane Library, EMBASE, Web of Science, CINAHL, ClinicalTrials, WHO-ICTRP, NHS Trusts, and ACTR were searched from the date of their inception up to November 28, 2021. We included cohort studies that assessed the association between serum B vitamins or B vitamins intake and the risk of dementia among older adults aged ≥60 years. The quality of all studies was assessed by the modified Newcastle-Ottawa Scale (NOS). The hazard ratios (HRs) and 95% CIs were calculated by the random effects model. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach was used to rate the certainty of evidence.


      Eleven cohort studies with sample sizes ranging from 233 to 3634 were included in the meta-analysis. Levels of serum folate showed statistically significant association with the risk of dementia (≥10 nmol/L: HR 1.57, 95% CI 1.01-2.46, low certainty; <10 nmol/L: HR 0.93, 95% CI 0.88-0.99, very low certainty). However, levels of vitamin B6 intake showed no statistically significant effects on risk of dementia; levels of serum vitamin B12 and vitamin B12 intake also showed no statistically significant effects on risk of dementia in older adults.

      Conclusions and Implications

      The results from our meta-analysis suggest that vitamin B6, B12, and folate may not be modifiable risk factors for dementia among older adults. Current evidence on the relationship between vitamin B status and dementia is not sufficient for development of vitamin B recommendations. More high-quality cohort studies are needed to confirm the relationship between the two in the future.


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