*2.2. Inclusion Criteria and Data Abstraction*

The inclusion criteria of this review were the following; (1) observational, randomized controlled trials, clinical and laboratory studies published over past ten years; (2) studies published in English language; (3) published in peer-reviewed journals; and (4) descriptive and epidemiological or evaluation-based studies. The exploration of preventive relationship of vitamin E with mild cognitive impairment is relatively new. Therefore, we selected to assign a broad range of criteria including human and animals-based studies published in the 10 years of timeframe. Articles published before 2010, focused on other forms of dementia than MCI, grey literature, abstracts—only studies, and non-peer-reviewed articles were excluded. We also conducted a post-hoc search in July 2021 to update our literature matrix used for this review. Details about the search results were saved in the spreadsheet by the lead author. Titles and abstracts were screened for relevancy and eligibility. If found relevant, full-texts were read thoroughly and data were extracted in a standardized data collection form. Variables such as year of publication, study type, outcomes, key findings, neuroprotective role of vitamin E, and conclusions were tabulated in the data collection form.
