Abstract
B vitamins may lower the risk of dementia, yet epidemiological findings, mostly from countries with folic acid fortification, have remained inconsistent. We evaluated in a large French cohort of older persons the associations between dietary B vitamins and long-term incident dementia. We included 1321 participants from the Three-City Study who completed a 24 h dietary recall, were free of dementia at the time of diet assessment, and were followed for an average of 7.4 years. In Cox proportional hazards models adjusted for multiple potential confounders, including overall diet quality, higher intake of folate was inversely associated with the risk of dementia (p for trend = 0.02), with an approximately 50% lower risk for individuals in the highest compared to the lowest quintile of folate (HR = 0.47; 95% CI 0.28; 0.81). No association was found for vitamins B6 and B12. In conclusion, in a large French cohort with a relatively low baseline folate status (average intake = 278 µg/day), higher folate intakes were associated with a decreased risk of dementia.
Highlights
B vitamins have fundamental roles in the function of the central nervous system [1], and have been considered as promising candidates for the prevention of dementia and its major etiology, Alzheimer’s disease (AD)
We evaluated in a large cohort of older persons from France—a country not subject to folic acid fortification policy—the association between dietary B vitamins and the risk of dementia and AD over 10 years of follow-up
When we examined the risk of AD, we found similar associations of high folate with a lower risk of AD, the magnitude of associations was slightly weaker than those found with all-cause dementia (p for trend = 0.08 in the first model, HR for higher versus lower quintile of folate = 0.52, 95% CI = 0.28, 0.97; results are not shown in the tables) and relationships were attenuated and no longer statistically significant after further adjustments (p for trend = 0.17 in Model 2)
Summary
B vitamins have fundamental roles in the function of the central nervous system [1], and have been considered as promising candidates for the prevention of dementia and its major etiology, Alzheimer’s disease (AD). B vitamins (B6, folate, and B12) regulate homocysteine (Hcy) levels, and hyperhomocysteinemia is a major vascular risk factor and an established risk factor for dementia [2]. Hyperhomocysteinemia may affect brain function through both vascular mediation and neurotoxicity [3]. B vitamins may have a direct effect on the brain, independently of homocysteine [4]. A lower status in B vitamins decreases S-adenosylmethionine, a major intermediate of methylation reactions in the brain which are involved in synaptic transmission and epigenetic regulation [5]. Tetrahydrofolate, the active form of folate, is involved in DNA repair system [6] and DNA replication, which are both critical for adult hippocampal neurogenesis [7]
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