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

Shenhong Ma ¹ Weisheng Zhuang ^1,2* Xu Wang ¹ Di Zhang ¹ Heling Wang ¹ Qiaohua Han ³ Qixin Ding ¹ Yuefang Li ³ Wanyue Li ⁴ Tianshu Li ⁵

• ¹ School of Rehabilitation Medicine, Henan University of Chinese Medicine, Zhengzhou, Henan Province, China
• ² Henan Provincial People's Hospital, Zhengzhou, China
• ³ School of Clinical Medicine, Henan University, Zhengzhou, Henan Province, China
• ⁴ Department of Radiology, Henan Provincial People's Hospital, Zhengzhou, Hunan Province, China
• ⁵ Zhengzhou First People's Hospital, Zhengzhou, Henan Province, China

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 minutes (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.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.