Transcranial direct current stimulation (tDCS) in elderly with mild cognitive impairment: A pilot study

ABSTRACT. Transcranial direct current stimulation (tDCS) is a non-invasive, painless and easy-to use-technology. It can be used in depression, schizophrenia and other neurological disorders. There are no studies about longer usage protocols regarding the ideal duration and weekly frequency of tDCS. Objective: to study the use of tDCS twice a week for longer periods to improve memory in elderly with MCI. Methods: a randomized double-blind controlled trial of anodal tDCS on cognition of 58 elderly aged over 60 years was conducted. A current of 2.0 mA was applied for 30 minutes for 10 sessions, twice a week. The anode was placed over the left dorsolateral prefrontal cortex (LDLFC). Subjects were evaluated before and after 10 sessions by the following tests: CAMCOG, Mini-Mental State Examination (MMSE), Trail Making, Semantic Verbal Fluency (Animals), Boston naming, Clock Drawing Test, Word list memory (WLMT), Direct and Indirect Digit Order (WAIS-III and WMS-III) and N-back. Results: After 10 sessions of tDCS, significant group-time interactions were found for the CAMCOG - executive functioning (χ2 = 3.961, p = 0.047), CAMCOG - verbal fluency (χ2 = 3.869, p = 0.049), CAMCOG - Memory recall (χ2 = 9.749, p = 0.004), and WMLT - recall (χ2 = 7.254, p = 0.007). A decline in performance on the CAMCOG - constructional praxis (χ2 = 4.371, p = 0.037) was found in the tDCS group after intervention. No significant differences were observed between the tDCS and Sham groups for any other tasks. Conclusion: tDCS at 2 mA for 30 min twice a week over 5 consecutive weeks proved superior to placebo (Sham) for improving memory recall, verbal fluency and executive functioning in elderly with MCI.

摘要。经颅直流电刺激（transcranial direct current stimulation, tDCS）是一种无创、无痛且操作简便的技术，可应用于抑郁症、精神分裂症及其他神经系统疾病的干预。目前尚无针对经颅直流电刺激理想时长与每周使用频次的长期应用方案相关研究。本研究旨在探讨每周两次、长期使用经颅直流电刺激对轻度认知障碍（MCI）老年患者记忆功能的改善效果。
方法：本研究采用随机双盲对照试验设计，纳入58名60岁以上老年受试者，对其左侧背外侧前额叶皮层（left dorsolateral prefrontal cortex, LDLFC）施加阳极经颅直流电刺激，以评估该刺激对认知功能的影响。试验参数为：电流强度2.0 mA，每次刺激时长30分钟，共完成10次刺激，每周两次。受试者分别在刺激疗程开始前及10次刺激结束后接受以下量表评估：剑桥认知检查（CAMCOG）、简易精神状态检查（Mini-Mental State Examination, MMSE）、连线测验、语义言语流畅性测验（动物类别）、波士顿命名测验、画钟测验、词语列表记忆测验（Word list memory, WLMT）、直接与间接数字顺序测验（WAIS-III及WMS-III）以及N-back任务。
结果：经10次经颅直流电刺激后，在以下维度观察到显著的组间-时间交互效应：剑桥认知检查-执行功能（χ²=3.961，p=0.047）、剑桥认知检查-言语流畅性（χ²=3.869，p=0.049）、剑桥认知检查-记忆回忆（χ²=9.749，p=0.004）以及词语列表记忆测验-回忆成绩（χ²=7.254，p=0.007）。干预后，经颅直流电刺激组在剑桥认知检查-结构性运用能力维度出现成绩下降（χ²=4.371，p=0.037）。其余评估任务中，经颅直流电刺激组与假刺激组均未观察到显著组间差异。
结论：以2 mA电流强度、每次30分钟、每周两次、连续5周的方案实施经颅直流电刺激，在改善轻度认知障碍老年患者的记忆回忆、言语流畅性与执行功能方面，效果显著优于安慰剂（假刺激）组。