From the most often cited study by Sano and colleagues, it was concluded that in patients with moderately severe impairment from Alzheimer's disease, treatment with selegiline or high dose Vitamin E slowed the progression to primary endpoints - death, institutionalization, loss of the ability to perform basic activities of daily living, or severe dementia. A total of 341 patients received the selegiline 10 mg/day, Vitamin E, 2000 IU/day, both selegiline and Vitamin E, or placebo for two years under double blind conditions. A common criticism of this study is covariate analysis had to be used before a treatment effect could be demonstrated because the placebo and active treatment groups had significantly different baseline MMSE scores. Because of Vitamin E’s numerical, but not statistically significant advantage over selegiline in this study, favorable adverse effect profile, and considerably lesser cost, it is considered to be the preferred treatment.

High doses of Vitamin E have been associated with increased clotting time, easy bleeding and bruising. Due to the increased risk of bleeding, concomitant use with warfarin or NSAIDs may be problematic.