Efficacy of transcranial direct current stimulation on cognitive function in patients with Parkinson's disease: a systematic review and meta-analysis.

OBJECTIVE

To assess the therapeutic effect of tDCS on cognitive function in patients with Parkinson's disease.

METHODS

From the start of the library's construction until June 24, 2024, we searched the following databases for literature: PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang, China Science and Technology Journal Database (VIP), and China Biomedical Literature Database (CBM). We also looked through the references in the articles. The improvement of overall cognition in patients with Parkinson's disease with tDCS was the primary outcome indicator. The improvement of executive function, memory, attention, language, quality of life, and depression with tDCS were the secondary outcome indicators. Two researchers extracted data independently, with a third researcher mediating in the event of a dispute. The Cochrane risk of bias tool was used to evaluate the quality of the included literature.

RESULTS

A total of 23 articles encompassing 874 subjects were included. tDCS has shown significant efficacy on overall cognition (SMD = 0.73, 95% CI = 0.57 to 0.89, I2 = 0%, P < 0.00001), particularly in the areas of executive function (SMD = -0.32, 95% CI = -0.56 to -0.07, I2 = 0%, P = 0.01) and language function (SMD = 0.5, 95% CI = 0.2 to 0.8, I2 = 0%, P = 0.001). Furthermore, the clinical efficacy of tDCS was enhanced with a stimulation intensity of 2 mA (SMD = 0.76, 95% CI = 0.58 to 0.93, I2 = 7%, P < 0.00001), a stimulation duration of ≥25 min (SMD = 0.70, 95% CI = 0.49 to 0.91, I2 = 6%, P < 0.00001), and a minimum of 10 stimulation sessions (SMD = 0.74, 95% CI = 0.56 to 0.92, I2 = 0%, P < 0.00001). Furthermore, tDCS has shown efficacy in alleviating depressive mood (SMD = -0.46, 95% CI = -0.79 to -0.13, I2 = 0%, P = 0.006).

CONCLUSION

tDCS demonstrated substantial efficacy in enhancing overall cognition in patients with PD. The efficacy of tDCS was obvious in executive function, language, and depressive mood. Nonetheless, a substantial quantity of rigorous clinical trials on tDCS for cognitive function in patients with PD remains necessary in the future.