Can exercise combined with transcranial direct current stimulation improve cognitive function in older adults? A...

This study investigated whether combining exercise with transcranial direct current stimulation (tDCS) improves overall cognition, memory, and executive function in older adults.

Following PRISMA guidelines, we systematically searched databases including PubMed, Web of Science, CNKI, and Wan Fang for randomized controlled trials (RCTs) examining the combined effect of exercise and tDCS on cognitive function in older adults. Used RStudio (version 4.2.0) to merge effect sizes and represent them as SMD with a 95% confidence interval (CI). The main effects are synthesized using a random effects model, and heterogeneity sources are explored through subgroup regression and sensitivity analysis.

The combined exercise and tDCS intervention significantly improved global cognitive function in older adults (SMD = 0.62, 95% CI: 0.36 to 0.89, p < 0.0001). Significant enhancements were observed in executive function (SMD = 0.54, 95% CI: 0.16 to 0.92, p = 0.005) and general cognitive ability (SMD = 0.75, 95% CI: 0.21 to 1.30, p = 0.006), while memory showed a non-significant improvement (SMD = 0.58, 95% CI: -0.03 to 1.19, p = 0.063). Both interventions lasting less than 6 weeks (SMD = 0.94, 95% CI: 0.60 to 1.27, p < 0.0001) and those lasting 6 weeks or longer (SMD = 0.24, 95% CI: 0.10 to 0.37, p = 0.0006) positively impacted cognitive function. However, the effect size was larger for cognitively healthy older adults (SMD = 0.69, 95% CI: 0.20 to 1.18, p = 0.006) compared to those with cognitive impairment (SMD = 0.60, 95% CI: 0.29 to 0.92, p = 0.0002). The combination of tDCS and integrated exercise produced the largest effect size (SMD = 1.74), despite high heterogeneity, while the combination of tDCS and Tai Chi produced the smallest but most robust effect (SMD = 0.25, I ² = 0%), indicating that exercise type significantly regulates the intervention effect of tDCS (p = 0.0015). Regression analysis shows that tDCS stimulation time has a significant positive regulatory effect on cognitive function in elderly people (p = 0.0002), while the combined intervention period (p = 0.030) and single exercise time (p = 0.034) both have a significant negative regulatory effect.

Based on limited evidence, we found that a combined intervention of exercise and tDCS is a potentially effective means of improving cognitive function in older adults. However, the extent of improvement varies with the cognitive domain, baseline performance level, and intervention plan.