Personalized assessment of high-definition slow-oscillatory transcranial direct current stimulation (so-tDCS) in older adults with sleep and subjective cognitive complaints: A study protocol for a randomized clinical trial.
This paper describes a protocol for a randomized, double-blind, sham-controlled clinical trial to assess whether high-definition slow-oscillatory transcranial direct current stimulation (so-tDCS) can concurrently improve subjective cognitive decline and sleep disturbances in older adults, with personalized neurophysiological monitoring via electrode-skin impedance.
Key Findings
Background
Subjective cognitive decline (SCD) is recognized as an early and potentially modifiable stage in the trajectory of neurodegenerative diseases.
Untreated sleep disturbances in older adults with SCD may accelerate the neurodegenerative process.
Proposed mechanisms include amyloid-beta accumulation.
Sleep disturbances may contribute to more rapid cognitive deterioration in this population.
Currently, non-pharmacological treatment options that concurrently manage SCD and sleep disturbances remain scarce.
Methods
The trial is designed as a randomized, double-blind, sham-controlled clinical trial targeting right-handed Chinese older adults with both SCD and sleep disturbances.
Participants will be randomly assigned to either high-definition 0.75 Hz so-tDCS or sham stimulation.
Each group will include 40 participants, for a total of 80 participants.
The intervention period is 4 weeks in duration.
The study is registered at ClinicalTrials.gov (Identifier: NCT07433738).
Methods
The trial employs a multimodal outcome assessment strategy evaluated at four time points.
Outcome measures include galvanic skin response, subjective cognitive complaints, sleep quality, salivary amyloid-beta levels, and domain-specific cognitive performance.
Assessments occur at baseline, week 4 (immediately post-intervention), and follow-up at weeks 8 and 12.
Salivary amyloid-beta levels are included as a biomarker outcome, reflecting interest in the amyloid-beta accumulation mechanism.
Domain-specific cognitive performance is assessed to capture targeted cognitive effects.
Background
High-definition so-tDCS uses a frequency of 0.75 Hz and is described as a frequency-specific neuromodulation technique designed to enhance brain health and cognition.
The technique is characterized as 'an emerging, frequency-specific neuromodulation technique.'
It is applied in a high-definition configuration, which differs from conventional tDCS electrode arrangements.
The stimulation targets slow-oscillatory brain activity relevant to sleep and memory consolidation.
Methods
Personalized neurophysiological monitoring via electrode-skin impedance measurement is incorporated as a key methodological feature of the trial.
Electrode-skin impedance is described as the personalized neurophysiological signal to be monitored using 'state-of-the-art measurement during so-tDCS.'
This monitoring is described as an 'add-on' setting that enables 'easy, quick and quantitative' evaluation of real-time neurophysiological signals.
The authors state this approach is intended to facilitate 'the incorporation of transcranial brain stimulation into clinical practice.'
Galvanic skin response is also included as an outcome measure alongside impedance monitoring.
What This Means
This research describes the design of a clinical trial testing whether a specialized form of brain stimulation called high-definition slow-oscillatory transcranial direct current stimulation (so-tDCS) can help older adults who are experiencing both early memory and thinking concerns (called subjective cognitive decline) and sleep problems. The study will enroll 80 participants who will receive either real brain stimulation or a fake (sham) version for four weeks, and researchers will track changes in sleep quality, cognitive function, and even a biological marker in saliva related to Alzheimer's-associated protein (amyloid-beta) over three months of follow-up.
A distinctive feature of this trial is the use of real-time personalized monitoring of the electrical connection between the stimulation electrodes and the skin (electrode-skin impedance). This is intended to give clinicians and researchers immediate, quantitative feedback about how the stimulation is being delivered to each individual, making the treatment more personalized and potentially easier to use in real-world healthcare settings.
This research suggests that combining a non-drug brain stimulation approach with individualized physiological monitoring could offer a new way to simultaneously address both cognitive and sleep concerns in aging populations. If successful, this approach could help fill a gap in care, as currently there are few non-pharmacological options that target both sleep disturbances and early cognitive decline together. The results of this trial are not yet available, as this paper reports only the study protocol.
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Lu H, Ni X, Yang N, Yuen Y, Gong Y, Ma S. (2026). Personalized assessment of high-definition slow-oscillatory transcranial direct current stimulation (so-tDCS) in older adults with sleep and subjective cognitive complaints: A study protocol for a randomized clinical trial.. PloS one. https://doi.org/10.1371/journal.pone.0360573