A SYSTEMATIC REVIEW OF OBSERVATIONAL STUDIES ASSESSING THE IMPACT OF OXIDATIVE STRESS IN COGNITIVE DECLINE.

Objective Introduction: Cognitive functions are defined as the mental processes through which information is received, processed, stored, and retrieved. Oxidation is considered as an important factor that affects negatively the brain function. The aim: To assess the impact of oxidative stress, as it is measured by oxidative markers or by the presence of anti-oxidants, on cognitive decline. Patients and methods Materials and methods: A systematic review of published observational studies in PubMed and in Scopus was performed. During the review process the keywords were used as follows: ("oxidative stress") AND ("cognitive decline" OR "cognitive dysfunction" OR "cognitive impairment" OR "cognitive deficiency") AND ("observational study" OR "cross sectional study" OR "prospective study" OR "retrospective study" OR "cohort study"). The search was conducted for the years from 2016 to 2020. Conclusion Conclusions: Seventy-four eligible studies were identified. Thirteen studies met the inclusion and quality criteria and were included in the systematic review. The studies conducted in ten different countries. Information about oxidative stress biomarkers is available in eight studies, while information about antioxidant factors is in ten studies. In all the thirteen studies the cognitive function was assessed with specific tools - scales. In the majority of studies, the presence of high scores in oxidative markers was positively associated with cognitive decline, while higher levels of antioxidant markers were associated with better cognitive function. Our results indicate that oxidative stress may be significantly associated with cognitive decline. The presence of the antioxidants glutathione, uric acid, melatonin, cysteine and peroxide dismutase has a positive effect on cognitive function.