MicroRNAs and mild cognitive impairment: A systematic review

•A data extraction form section was specifically designed for laboratory procedures.•Available evidence on miRNAs as biomarkers for MCI is currently still inconsistent.•Further, high-quality, studies on independent cohorts are needed.•Heterogeneity of results could be due to a high variability in laboratory procedures.•Meta-analysis of data was inappropriate due to the heterogeneity of included studies.