Efficacy of transcranial direct current stimulation on cognitive function in post stroke cognitive impairment: A systematic review and meta-analysis of randomized controlled trials

Background Post-stroke cognitive impairment (PSCI) significantly hinders recovery. Transcranial direct current stimulation (tDCS) is a promising intervention, yet its efficacy varies, and the optimal therapeutic window remains debated.Objectives To evaluate the efficacy of tDCS on global cognition, memory, and executive function in PSCI and determine if stroke onset duration influences treatment outcomes.Methods We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) searched from databases including PubMed, Embase, and Cochrane Library up to January 2026. Outcomes included Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE), memory, and executive function. Subgroup analyses stratified patients by stroke chronicity (<6 months vs. >6 months).Results Twenty RCTs involving 772 patients were included. tDCS significantly improved global cognition (MoCA: MD = 2.11, 95% CI [0.93, 3.30], p = 0.0005). Crucially, subgroup analysis revealed significant cognitive improvement in patients treated within 6 months post-stroke (MD = 2.51, p < 0.0001), whereas those treated after 6 months showed no significant benefit (MD = 0.37, p = 0.38). Significant improvements were also observed in memory and executive function.Conclusions tDCS effectively enhances cognition in PSCI. However, efficacy is time-dependent, suggesting a “critical window” for intervention within the first 6 months post-stroke. Early application is recommended.Registration number CRD42024543596