Effects of transcranial direct current stimulation on dual-task performance in older and young adults: A systematic review and meta-analysis

•Transcranial direct current stimulation (tDCS) improves dual-task (DT) performance.•Active tDCS significantly reduced dual-task cost on gait speed in older adults (OA).•Active tDCS significantly improved dual-task postural sway velocity in older adults.•Active tDCS significantly reduced DT cost on postural sway velocity and area in OA.•No significant difference between active and sham tDCS on outcomes in young adults. The ability to successfully perform various physical and cognitive tasks simultaneously is a required goal for older adults (OA). Brain areas such as the dorsolateral prefrontal cortex (DLPFC) are involved in cognitive processing during walking and balance tasks, with transcranial direct current stimulation (tDCS) used in modulating the excitability of brain cortical areas such as the DLPFC. To evaluate the available scientific evidence on the effects of tDCS on dual-task (DT) Performance (PF) in older and young adults. Databases of PEDro, Web of Science, PubMed, Embase, and Cochrane Library were searched from inception until December 2023. RCTs were included. The risk of bias (ROB) and methodological quality of the included RCTs were assessed with the appropriate Cochrane ROB assessment tool, and PEDro scale respectively. Both narrative and quantitative synthesis were used for data analysis. The result revealed that real tDCS significantly reduced: dual-task cost (DTC) on gait speed (MD = 3.68, 95 %CI-1.04 to 6.33, P = 0.006), DTC on postural sway (PS) velocity (MD = -25.49, P < 0.00001), DTC on PS area (MD = -53.96, P < 0.00001), and significantly improved DT PS velocity (SMD = -0.61, P = 0.02), with low certainty of evidence post- experiment compared to sham tDCS in OA. However, in young adults, there was no significant difference post-experiment between real and sham tDCS on DT stride time variability (P = 0.18) and DTC on stride time variability (P = 0.34) with low certainty of evidence. tDCS especially anodal tDCS to the DLPFC significantly improved DT PS velocity and area, and also significantly reduced DTC on gait speed, PS velocity, and area in OA.