**1. Introduction**

Dementia is a serious public health concern with nearly 50 million people having some form of dementia globally [1]. Reportedly, about 60% of the dementia population live in low and middle-income countries (LMICs) [1]. Estimates suggest that about 10 million people get dementia every year and about 15–20% of elderly population reported having mild cognitive impairment (MCI) as the early stage of dementia [1–3]. MCI causes a slight but observable and measurable decline in the memory and thinking skills of an individual. In some individuals, MCI can be reversible (if physiological in origin), however, the likelihood of the reversal to the normal cognitive capability is less for majority of people if it is pathological [2,3]. With due course, MCI advances to the next stage with nearly 65% of people developing more severe forms [2,3].

According to the previous meta-analytical evidence presented by the American Academy of Neurology, the prevalence of MCI was nearly 7% among people with age 60–64 years, which increases with advancing age [3,4]. In the United States (U.S.), the highest prevalence was reported among elderly above 75 years of age [4]. These trends are not only limited to developed countries, low- and middle-income countries indicate

**Citation:** Lakhan, R.; Sharma, M.; Batra, K.; Beatty, F.B. The Role of Vitamin E in Slowing Down Mild Cognitive Impairment: A Narrative Review. *Healthcare* **2021**, *9*, 1573. https://doi.org/10.3390/ healthcare9111573

Academic Editor: Phyo Kyaw Myint

Received: 18 October 2021 Accepted: 17 November 2021 Published: 18 November 2021

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similar patterns [5]. However, due to lack of population-based studies, the true estimates are unavailable. According to the previous reports, the prevalence of MCI ranged from 4.5% to 15.4% among South Asian countries [6–9]. Differences in MCI by demographic characteristics (e.g., gender, race/ethnicity, education) were also noted with women being at greater lifetime risk for dementia compared to their male counterparts [10–12]. The occurrence of MCI is found delayed and lenient towards the end of life among whites and highly educated people while the onset of MCI is observed at younger age among blacks and those with lower education attainment [10–12]. The lifetime risk of dementia is 21% among men with an associate degree while it is 35% for those who have less than high school education [10–12]. White women have a shorter cognitively impaired life compared to black women (6 years vs. 12 to 13 years) [10–12]. The burden of dementia further translates into higher cost associated with its management [2]. According to the Alzheimer association, through identification of early stages of Alzheimer disease (AD) i.e., MCI, nearly \$7 to \$7.9 trillion in health and long-term care can be saved [2].

MCI has severe implications for the patients and their family members and challenges are multifactorial in origin [13]. Often time patients and their family members are unable to identify cognitive decline at earlier stages, particularly in older population groups, in whom cognitive decline is a normal physiological phenomenon. Moreover, cooccurrence of other age-associated diseases are likely to occur in this group with a limited ability to make a differential diagnosis [14,15]. Cognitive insufficiency impacts the quality of life, individual's functioning, their relationship with the family members, and their self-esteem [14,15]. Caregivers experience high level of caregiving burden for the larger population of MCI [16]. Given the unavailability of medication to treat, prevent, or slow the progression of MCI to dementia, preventive strategies take precedence for at-risk population groups to prevent progressive deficits [17]. Prevention of somatic diseases, promotion of physical and mental exercise, cognitive training, avoidance of toxins, reduction in stress, stopping smoking, and use of dietary compounds such as antioxidants and supplements are some of the suggested to address MCI [17,18]. Among antioxidants, vitamins play a critical role in reducing or delaying to the process of cognitive decline in people with MCI. Among all vitamins, vitamin E was found to be effective in reducing MCI [17–23]. Vitamin E is a fat-soluble vitamin and found in variety of foods [19]. Its usable form (i.e., alpha tocopherol) is considered a scavenger of free radicals in the body [19], which controls brain prostaglandin synthesis and regulates nucleic acid synthesis. While some studies have documented association of vitamin E intake in slowing down the progression of MCI, collective evidence to investigate its significance is still lacking [17–23]. Therefore, the purpose of this study was to review existing literature to decipher role of vitamin E in slowing down MCI progression.
