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The link between vitamin B levels and subsequent cognitive function remains unclear

Minimal data support an association between low blood levels of vitamins B-6 and B-12, and cognitive function in the elderly, according to a recent meta-analysis of studies on the topic. Although low baseline blood folate levels predicted poorer cognitive function at follow-up in the majority of studies, the poor quality and diverse methodology of studies diminished the validity of the finding reported. Thus, the link between vitamin B status and subsequent cognitive function remains unclear, conclude researchers at the Tufts New England Medical Center Evidence-Based Practice Center.

The researchers systematically reviewed studies that evaluated the link between folate, vitamin B-6, vitamin B-12, and cognitive function in the elderly. Of the 24 studies included in analysis, 16 were rated as only fair in quality. The majority of studies failed to report definitions of normal vitamin B ranges for the elderly and varied in their definition of low vitamin B status. The studies varied widely in the methods used to assess the same cognitive domains, making cross comparisons among studies unreliable.

Six of 10 folate studies reported a significant association between low baseline blood folate concentrations and subsequent poor global cognitive test performance; 4 of 9 folate studies found associations between low blood folate concentrations and increased prevalence of Alzheimer's disease. However, data supporting these associations was weak due to the use of diverse methods of assessing cognition and lack of standardized cut-points for categorizing low vitamin B status.

The study was supported in part by the Agency for Healthcare Research and Quality (contract no. 290-02-0023).

See "Heterogeneity and lack of good quality studies limit association between folate, vitamins B-6 and B-12, and cognitive function," by Gowri Raman, Athina Tatsioni, Mei Chung, and others, in the July 2007 Journal of Nutrition 137(7), pp. 1789-1794.

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