There is no evidence that Vitamin E supplementation, in the alpha-tocopherol form, given to people with mild cognitive impairment (MCI) would help to prevent or delay the progression to dementia. Similarly, there is no evidence that Vitamin E supplementation improves cognitive function in people with MCI or dementia due to Alzheimer’s Disease.
Farina, N. Llewellyn, D. [and] Isaac, MGEKN. [et al] (2017). Vitamin E for Alzheimer’s dementia and mild cognitive impairment. Cochrane Database of Systematic Reviews. April 2017, 18; 4: CD002854.
There is also an Executive Summary.
“…further research is quite likely to affect the results”.