The study focused on 1,994 participants without dementia at baseline, with an average age of 60 years. Each participant had at least 2 measurements of a combined indicator of vitamin B12 status (3cB12) along with a series of neuropsychological assessments that measured memory, executive function, and language ability. This research tracked these measures over time to evaluate how cognitive performance changed in relation to vitamin B12 levels.
Using adjusted linear mixed effects models, the team estimated the rate of annual cognitive change across four quartiles of B12 levels. The participants in the highest quartile demonstrated significantly slower declines across all 3 major cognitive domains when compared with those in the lowest quartile.
Specifically, individuals in the top 25% of B12 status showed a slower decline in memory (β = 0.0071; 95% CI = 0.003–0.01), executive function (β = 0.0056; 95% CI = 0.0009–0.01), and language (β = 0.0090; 95% CI = 0.004–0.01). Over a 10-year span, this equates to roughly 0.05 to 0.09 standard deviation less cognitive decline, especially when accumulated over time.
The study also examined whether the relationship between vitamin B12 and cognition was influenced by folate levels, another B vitamin known to interact with B12 in the body. The participants were categorized into an elevated folate (≥20 ng/mL) group and non-elevated folate (6–19 ng/mL) group.
The results showed that the positive link between higher B12 and better memory outcomes was particularly robust among individuals with elevated folate. However, the protective association between B12 and other cognitive functions (executive function and language) remained consistent regardless of folate status.
The results suggest that low B12 levels in mid- to late adulthood could be a subtle but significant contributor to age-related cognitive decline, even in people who do not yet show symptoms of dementia. Given that vitamin B12 deficiency is relatively common in older adults these findings illuminate the importance of regular monitoring and adequate intake through diet or supplements.
Source:
Marino, F. R., Rogers, G., Miller, J. W., Selhub, J., Mez, J., Crane, P. K., Mukherjee, S., Saykin, A. J., Hohman, T. J., Trittschuh, E. H., Au, R., Jacques, P. F., & Hwang, P. H. (2025). Higher vitamin B12 from mid- to late life is related to slower rates of cognitive decline. Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, 21(10), e70864. https://doi.org/10.1002/alz.70864
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