Serum levels of vitamin E forms and risk of cognitive impairment in a Finnish cohort of older adults

Background: Vitamin E includes eight natural antioxidant compounds (four tocopherols and four tocotrienols), but a-tocopherol has been the main focus of investigation in studies of cognitive impairment and Alzheimer's disease. Objective: To investigate the association between serum levels of tocopherols and tocotrienols, markers of vitamin E oxidative/nitrosative damage (alpha-tocopherylquinone, 5-nitro-gamma-tocopherol) and incidence of cognitive impairment in a population-based study. Design: A sample of 140 non-cognitively impaired elderly subjects derived from the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study was followed-up for 8 years to detect cognitive impairment, defined as development of mild cognitive impairment (MCI) or Alzheimer's dementia. The association between baseline serum vitamin E and cognitive impairment was analyzed with multiple logistic regression after adjusting for several confounders. Results: The risk of cognitive impairment was lower in subjects in the middle tertile of the alpha-tocopherol/cholesterol ratio than in those in the lowest tertile: the multiadjusted odds ratio (OR) with 95% confidence interval (CI) was 0.27 (0.10-0.78). Higher incidence of cognitive impairment was found in the middle [OR (95% CI): 3.41 (1.29-9.06)] and highest [OR (95% CI): 2.89 (1.05-7.97)] tertiles of the 5-NO2-gamma-tocopherol/gamma-tocopherol ratio. Analyses of absolute serum levels of vitamin E showed lower risk of cognitive impairment in subjects with higher levels of gamma-tocopherol, beta-tocotrienol, and total tocotrienols. Conclusions: Elevated levels of tocopherol and tocotrienol forms are associated with reduced risk of cognitive impairment in older adults. The association is modulated by concurrent cholesterol concentration. Various vitamin E forms might play a role in cognitive impairment, and their evaluation can provide a more accurate measure of vitamin E status in humans. (C) 2013 Elsevier Inc. All rights reserved.