Folate, Vitamin B6 and Vitamin B12 Intake and Mild Cognitive Impairment and Probable Dementia in the Women’s Health Initiative Memory Study
Jessica C. Agnew-Blais, ScD,1Sylvia Wassertheil-Smoller, PhD,2Jae H. Kang, DSc,3Patricia E. Hogan, MS, MPH,4Laura H. Coker, PhD,5Linda G. Snetselaar, RD, PhD,6 and Jordan W. Smoller, MD, ScD7
Whether higher B vitamin (B6, B12, and folate) intake is protective against cognitive decline in later life remains uncertain. Several prospective, observational studies find higher B vitamin intake to be associated with lower risk of dementia; other studies, including most trials of B vitamin supplementation, observe no effect on cognition. We examine this question in a large population of older women carefully monitored for development of mild cognitive impairment (MCI) and probable dementia.
To determine whether baseline folate, vitamin B6 and/or B12 intake, alone or in combination, are associated with incident MCI/probable dementia among older women.
Prospective, longitudinal cohort study. B vitamin intake was self-reported using a food frequency questionnaire administered at baseline between May 1996 and December 1999.
Postmenopausal women (n=7,030) free of MCI/probable dementia at baseline in the Women’s Health Initiative Memory Study.
Main outcome measures
Over a mean follow-up of 5.0 years, 238 cases of incident MCI and 69 cases of probable dementia were identified through rigorous screening and expert adjudication.
Cox proportional hazard models adjusting for sociodemographic and lifestyle factors examined the association of B vitamin intake above and below the recommended daily allowance and incident MCI/probable dementia.
Folate intake below the RDA at study baseline was associated with increased risk of incident MCI/probable dementia (HR=2.0, 95% CI: 1.3, 2.9), after controlling for multiple confounders. There were no significant associations between vitamins B6 or B12 and MCI/probable dementia, nor any evidence of an interaction between these vitamins and folate intake.
Folate intake below the RDA may increase risk for MCI/probable dementia in later life. Future research should include long-term trials of folic acid supplementation to examine whether folate may impart a protective effect on cognition in later life.
Resource: J Acad Nutr Diet. 2015 Feb; 115(2): 231–241.