Effects of non-invasive brain stimulation combined with cognitive training on cognitive functions in older people with mild cognitive impairment: a systematic review with meta-analysis

Background: Non-invasive brain stimulation (NIBS) has emerged as a potential adjunct to cognitive training for enhancing cognitive performance in older people with mild cognitive impairment (MCI). This systematic review and meta-analysis evaluated the efficacy of combined NIBS and cognitive training on cognitive function in this population. Methods: Comprehensive searches were conducted in PubMed, EBSCOhost, CINAHL Complete, Cochrane Library, ProQuest, Scopus, and Web of Science up to May 2025. The review followed PRISMA guidelines; methodological quality and certainty of evidence were assessed using the Oxford Centre for Evidence-Based Medicine levels, Cochrane Risk of Bias 2 (RoB 2), and GRADE. The protocol was registered in PROSPERO (CRD42024563219). Eligible randomized controlled trials assessed NIBS plus cognitive training on cognitive outcomes in older people with MCI. Results: Of 1,689 records, 10 studies met inclusion criteria. The combined intervention showed a moderate positive effect on attention/processing speed via Trail-Making Test Part A (TMT-A; effect size = 0.54). Improvements were also observed in global cognition (MoCA), though not statistically significant (p > 0.05). No significant effects were found for TMT-B (effect sizes 0.05–0.52). Conclusion: NIBS combined with cognitive training yields beneficial effects on specific cognitive domains, particularly attention and processing speed, in older people with MCI. Further high-quality randomized controlled trials are warranted. Systematic review registration: CRD42024563219.