Most people are familiar with metformin as a diabetic treatment option. Different positive benefits have been found for it, in addition to its anti-diabetes properties. Cognitive function enhancement is the most recent characteristic that has been studied. This study aimed to look at the evidence on the effects of metformin on cognitive performance. Web of Science, PubMed, Scopus, the Cochrane Library, EMBASE, and PsycINFO databases were searched systematically. After eliminating duplicates and irrelevant documents, the findings were screened. The documents that remained were scanned and data were extracted. Nineteen studies were qualified for meta-analysis after evaluating 3827 identified records. There was no significant relationship between metformin therapy and cognitive performance in none of the studies including cross-sectionals, cohorts, and clinical trials (p > 0.05). Results show that metformin has no significant effect on improving cognitive function or protecting against any dementia including vascular dementia and Alzheimer’s disease, and cognitive impairment as well.
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