Mild cognitive impairment (MCI) is a syndrome characterized by a decline in cognitive performance greater than expected for an individual's age and education level, but that does not interfere much with daily life activities. Establishing the prevalence of MCI is very important for both clinical and research fields. In fact, in a certain percentage of cases, MCI represents a prodromal condition for the development of dementia. Accordingly, it is important to identify the characteristics of MCI that allow us to predict the development of dementia. Also, initial detection of cognitive decline can allow the early implementation of prevention programs aimed at counteracting or slowing it down. To this end, it is important to have a clear picture of the prevalence of MCI and, consequently, of the diagnostic criteria used. According to these issues, this systematic review aims to analyze MCI prevalence, exploring the methods for diagnosing MCI that determine its prevalence. The review process was conducted according to the PRISMA statement. Three thousand one hundred twenty-one international articles were screened, and sixty-six were retained. In these studies, which involved 157,035 subjects, the prevalence of MCI ranged from 1.2 to 87%. The review results showed a large heterogeneity among studies due to differences in the subjects' recruitment, the diagnostic criteria, the assessed cognitive domains, and other methodological aspects that account for a higher range of MCI prevalence. This large heterogeneity prevents drawing any firm conclusion about the prevalence of MCI.

Cognitive reserve (CR) represents the ability to optimize performance and functioning to cope with brain damage or disease. CR reflects the capability to adaptively and flexibly use cognitive processes and brain networks to compensate for the deterioration typical of aging. Several studies have investigated the potential role of CR in aging, especially from the perspective of preventing and protecting against dementia and Mild Cognitive Impairment (MCI). This systematic literature review aimed to investigate the role of CR as a protective factor against MCI and associated cognitive decline. The review process was conducted according to the PRISMA statement. For this purpose, ten studies were analyzed. The results of this review show that high CR is significantly associated with a reduced risk of MCI. In addition, a significant positive relationship between CR and cognitive functioning is observed when comparing subjects with MCI and healthy subjects and within people with MCI. Thus, the results confirm the positive role of cognitive reserve in mitigating cognitive impairment. The evidence from this systematic review is consistent with the theoretical models of CR. Indeed, previous research hypothesized that specific individual experiences (such as leisure activities) allow a person to acquire successful neural resources over the years to cope with cognitive decline.

Introduction: Mild cognitive impairment (MCI) is a syndrome defined as a decline in cognitive performance greater than expected for an individual according to age and education level, not interfering notably with daily life activities. Many studies have focused on the memory domain in the analysis of MCI and more severe cases of dementia. One specific memory system is represented by autobiographical memory (AM), which has been largely studied in Alzheimer’s disease and its effect on AM; however, the impairment of AM in moderate forms of decline, such as MCI, is still controversial. Objective: The main aim of this systematic review is to analyze the functioning of autobiographical memory in patients with MCI, considering both the semantic and the episodic components. Materials: The review process was conducted according to the PRISMA statement. The search was conducted until 20 February 2023 in the following bibliographical databases: PubMed, Web of Science, Scopus, and PsycInfo, and twenty-one articles were included. Results: The results highlight controversial findings concerning the semantic component of AM since only seven studies have found a worse semantic AM performance in patients with MCI compared to the HC group. The results of impaired episodic AM in individuals with MCI are more consistent than those concerning semantic AM. Conclusions: Starting from the evidence of this systematic review, further studies should detect and investigate the cognitive and emotional mechanisms that undermine AM performance, allowing the development of specific interventions targeting these mechanisms.