Plasma antioxidants and risk of dementia in older adults.

Introduction: Plant-based diets rich in fruits and vegetables have been associated with lower risk of dementia, but the specific role of antioxidants, a key class of bioactive phytochemicals, has not been well ascertained.
Methods: We measured antioxidants in a case-cohort study nested within the Ginkgo Evaluation of Memory Study. We included 996 randomly selected participants and 521 participants who developed dementia, of which 351 were diagnosed with Alzheimer's disease (AD) during a median of 5.9 years of follow-up. We measured baseline plasma levels of retinol, α-, and γ-tocopherol; zeaxanthin and lutein (combined); beta-cryptoxanthin; cis-lycopene; trans-lycopene; α-carotene; and trans-β-carotene by organic phase extraction followed by chromatographic analysis and related these to neurologist-adjudicated risks of all-cause dementia and AD.
Results: Plasma retinol, α-, and γ-tocopherol, and carotenoids were not significantly related to risk of dementia or AD. Associations were not significant upon Bonferroni correction for multiple testing and were consistent within strata of sex, age, apolipoprotein E ε4 genotype, mild cognitive impairment at baseline, and intake of multivitamin, vitamin A or β-carotene, or vitamin E supplements. Higher trans-β-carotene tended to be related to a higher risk of dementia (adjusted hazard ratio [HR] per 1 standard deviation [SD] higher trans-β-carotene: 1.10; 95% confidence interval [CI]: 1.00, 1.20) and α-carotene tended to be associated with higher risk of AD only (adjusted HR per 1 SD higher α-carotene: 1.15; 95% CI: 1.02, 1.29).
Discussion: Plasma antioxidants were not significantly associated with risk of dementia or AD among older adults. Similar studies in younger populations are required to better understand the association between plasma antioxidants and dementia risk.
Competing Interests: Dr. DeKosky acknowledges payments as a dementia editor for UpToDate and payments from Acumen, Chair Medical Advisory Board (MAB); Biogen, Chair, DSMB; Cognition Therapeutics, Chair, MAB; Prevail Pharma, Chair, DSMB; Vaccinex, Inc, Chair, DSMB; and payments for his role as associate editor at Neurotherapeutics. Dr. Fitzpatrick acknowledges payments from Bloodm Hurst & O'Reardon, LLP; payments for Pulmonary Specialist‐Health Coach Consultation (PuSHCon) funded by NIH (UCSF); and honoraria as NIA‐S Study Section member. Dr. Lopez acknowledges payments from Biogen and Grifols. Dr. Kuller acknowledges payments from UpToDate for articles on Alzheimer ’s disease. Dr. Mukamal acknowledges grant support unrelated to this project from the US Highbush Blueberry Council, consulting fees from the University of Washington and Wolters Kluwer, payments from The Journal of Internal Medicine, and an advisory role for the University of Pittsburgh (no payments).
(© 2021 The Authors. Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring published by Wiley Periodicals, LLC on behalf of Alzheimer's Association.)