OBJECTIVES: To examine whether use of vitamins C or E alone or in combination was associated with lower incidence of dementia or Alzheimer's disease (AD).
DESIGN: Prospective cohort study.
SETTING: Group Health Cooperative, Seattle, Washington.
PARTICIPANTS: Two thousand nine hundred sixty-nine participants aged 65 and older without cognitive impairment at baseline in the Adult Changes in Thought study.
MEASUREMENTS: Participants were followed biennially to identify incident dementia and AD diagnosed according to standard criteria. Participants were considered to be users of vitamins C or E if they self-reported use for at least 1 week during the month before baseline.
RESULTS: Over a mean follow-up±standard deviation of 5.5±2.7 years, 405 subjects developed dementia (289 developed AD). The use of vitamin E was not associated with dementia (adjusted hazard ratio (HR)=0.98, 95% confidence interval (CI)=0.77–1.25) or with AD (HR=1.04; 95% CI=0.78–1.39). No association was found between vitamin C alone (dementia: HR=0.90, 95% CI=0.71–1.13; AD: HR=0.95, 95% CI=0.72–1.25) or concurrent use of vitamin C and E (dementia: HR=0.93, 95% CI=0.72–1.20; AD: HR=1.00, 95% CI=0.73–1.35) and either outcome.
CONCLUSION: In this study, the use of supplemental vitamin E and C, alone or in combination, did not reduce risk of AD or overall dementia over 5.5 years of follow-up.