Personalized Assessment of High-definition Slow-oscillatory Transcranial Direct Current Stimulation (So-tDCS) in Older Adults With Subjective Cognitive and Sleep Complaints

Background: Subjective cognitive decline (SCD) is considered to be the early risk stage of dementia. Untreated SCD comorbid with sleep disturbances may accelerate the progression of neurodegeneration (β-amyloid and tau) and lead to cognitive deficits. At present, non-pharmacological interventions for managing SCD and sleep disturbances are very limited. High-definition slow-oscillatory transcranial direct current stimulation (so-tDCS) is a newly developed frequency-specific modality of brain stimulation for promoting brain health and cognition. Notably, neurophysiological feature (impedance) during tDCS was found to be related to treatment outcomes and adverse effects (skin injury). Objectives: We propose to 1) develop a high-performing neurophysiological signal detector for tDCS and test its feasibility and flexibility in a randomized clinical trial; 2) investigate the short-term and long-term effects of high-definition so-tDCS on SCD, sleep quality and plasma Aβ and p-tau levels; 3) examine the values of neurophysiological signals in predicting the treatment outcomes at individual level. Design: A randomized, double-blind, sham-controlled trial. Methods: Chinese right-handed older adults with SCD and sleep disturbances will be randomly assigned to a 4-week intervention of either high-definition 0.75 Hz so-tDCS or sham tDCS, with 40 participants per arm. Pre-treatment magnetic resonance imaging (MRI) scans will be collected to exclude the cases with major neurological disease and quantify individual's brain features. Galvanic skin response, subjective cognitive complaints, sleep quality, plasma p-tau and β-amyloid levels and domain-specific cognition will be assessed at baseline, 4th week, 8th week and 12th week. Program adherence and adverse effects will be monitored throughout the whole intervention.