The team proposes a randomized, double-blind, sham-controlled clinical trial to test focal high-definition slow-oscillatory transcranial direct current stimulation in older adults who report both sleep problems and cognitive complaints. Enrollment targets right-handed Chinese adults aged 60–80 with preserved global cognition (HK‑MoCA > 26), a score indicating subjective cognitive decline (SCC total > 1 on the 10‑item questionnaire), and poor sleep quality defined by a Pittsburgh Sleep Quality Index (PSQI) total score > 5. Participants with diagnosed age-related neurodegenerative disease, major neurological events, or psychiatric disorders are excluded. The protocol is registered on ClinicalTrials.gov (Identifier: NCT07433738) and approved by the Joint CUHK NTEC‑CREC.
The intervention period spans four weeks with outcomes assessed at baseline, week 4 (post‑intervention), week 8, and week 12. The source reported a planned sample of 40 participants per arm; no additional sample‑size justification or statistical thresholds were provided in the article text.
Investigators will deliver high‑definition so-tDCS using a battery-driven DC-Stimulator Plus (NeuroConn). The montage is a 4×1 high‑definition configuration: a single anodal electrode centered over the left dorsolateral prefrontal cortex (F3) with four surrounding cathodal return electrodes. Each sponge electrode measures 1.2 cm in diameter and will be single‑use for safety. Active stimulation parameters are reported as a monophasic sinusoidal waveform at 0.75 Hz, 2 milliamps, for 20 minutes per session. The sham condition uses identical electrode placement and an initial 30‑second stimulation period to mimic cutaneous sensations; electrodes remain in place for the same total time without sustained current.
Sessions occur three times per week for four weeks for a scheduled total of 12 sessions per participant. The protocol instructs participants to relax during stimulation.
The trial designates three primary outcomes: changes in electrode–skin impedance measured via a built‑in wearable Galvanic Skin Response (GSR) sensor; changes in self‑reported subjective cognitive complaints using the study’s 10‑item SCC questionnaire (binary yes/no responses summed to a 0–10 score); and change in subjective sleep quality assessed with the PSQI (19 items yielding seven component scores and a total score with a cutpoint of 5 for disturbances).
Secondary outcomes include objective actigraphy (Philips Actiwatch 2) to quantify sleep–wake patterns and sleep efficiency, domain‑specific cognitive tests including attention metrics used to calculate intra‑individual variability of reaction time (expressed as ICV‑RT = [SD RT / mean RT] × 100), and salivary amyloid‑beta (Aβ42 and Aβ40) measured at baseline and week 4 by ELISA‑type methods. The article notes that salivary samples will be collected at consistent times to mitigate circadian variation.
The protocol places emphasis on real‑time monitoring of electrode–skin interface properties. A wearable GSR sensor placed on the fingers will record skin conductance signals during stimulation sessions to index the skin impedance component of the stimulation circuit. The authors framed impedance as relevant to both safety (for example, local skin reactions) and accurate dose delivery. The trial will therefore treat GSR‑derived metrics as both safety monitors and candidate predictors of individual treatment response. The source did not specify exact GSR thresholds for stopping rules or predefined impedance cutpoints.
High‑resolution structural MRI (3.0T Siemens MAGNETOM Prisma; T1‑weighted MPRAGE with 1 mm isotropic voxels) will be acquired for screening and to guide localization of the stimulation target. Surface‑based morphometry (cortical volume, thickness and folding) will be used to localize targets, correlate baseline neurophysiology with outcomes, and control for baseline brain features in group comparisons. Actigraphy devices will be worn continuously across multi‑day windows to provide objective sleep metrics that complement PSQI scores.
Cognitive phenotyping includes the attention network test from which intra‑individual variability measures (ICV‑RT) will be derived to capture within‑person fluctuations in reaction time; the protocol positions IIV measures as sensitive indicators of short‑term changes in cognitive function.
Randomization will be generated online by a statistician who is not otherwise involved in the study. Eligible participants are randomized 1:1 to active or sham stimulation. Both participants and outcome assessors are blinded to allocation. Written informed consent is required for participation; the protocol states that participants and their families will receive full briefings and that anonymity, privacy and confidentiality protections will be observed. The trial adheres to CONSORT and SPIRIT reporting frameworks and declares compliance with the Declaration of Helsinki and ICH‑GCP. Data access is restricted due to personal medical information; investigators indicate data requests can be made to the institutional data access/ethics committee.
The source article notes several open elements without detailed specification. The protocol reports group sizes (40 per arm) and assessment time points through 12 weeks, but it does not present a detailed statistical analysis plan or power calculations within the text. The manuscript emphasizes the value of GSR‑derived impedance signals but does not provide pre‑specified impedance safety thresholds or analytic thresholds for predicting clinical response. Longitudinal biomarker follow‑up beyond week 12 is not reported. Finally, while the study targets left DLPFC (F3) using MRI‑guided morphometrics, the article does not outline contingency plans for participants with MRI findings that preclude stimulation beyond standard exclusion criteria.
These aspects will require clarification in trial reports and any resulting publications. The registered trial identifier (NCT07433738) provides the public record for protocol details; investigators noted the trial will be reported according to major international journal standards.