Effects of tDCS on Cognitive Function in Older Adults With Subjective Cognitive Decline: Randomized Sham-Controlled Trial

N/AEnrolling By InvitationNCT07531888

Universidad Autónoma del Estado de Hidalgo20 enrolled

Overview

This randomized, double-blind, sham-controlled clinical trial evaluates the effects of transcranial direct current stimulation (tDCS) using the Sooma Oy device on cognitive function in older adults with Subjective Cognitive Decline (SCD). The study investigates changes in memory, executive function, attention, and global cognition after a structured intervention consisting of 22 intensive sessions and 8 maintenance sessions. Assessments occur at baseline, Week 4, Week 8, and Week 12.

This study uses the Sooma tDCS system (Sooma Oy, Finland) to deliver a current of 2 mA for 30 minutes per session. The anode is positioned over F3 (left dorsolateral prefrontal cortex) and the cathode over F4 (right dorsolateral prefrontal cortex), according to the international 10-20 system. Participants receive 22 intensive sessions (five days per week) followed by 8 weekly maintenance sessions. The sham condition mimics the stimulation procedure through a 30-second ramp-up and ramp-down period without sustained active stimulation. Primary and secondary outcomes focus on changes in cognitive function, assessed using validated neuropsychological instruments. In addition, the study includes the analysis of molecular biomarkers associated with calcium (Ca²⁺) homeostasis, as age-related changes disrupt multiple electrophysiological processes within the hippocampus. These alterations have been proposed as potential biomarkers of brain aging and are closely linked to cognitive decline. Biological samples will be obtained through buccal swabs using sterile cotton applicators from participating older adults. Total RNA will then be extracted using the TRIzol method, followed by the design of specific primer oligonucleotides and amplification using a commercial RT-PCR kit. This clinical trial aims to generate evidence on the therapeutic utility of tDCS in individuals with Subjective Cognitive Decline, supporting early intervention strategies and contributing to the identification of molecular correlates associated with cognitive changes.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

Interventions

Transcranial Direct Current StimulationDEVICE

Transcranial direct current stimulation (tDCS) is administered using the Sooma tDCS system (Sooma Oy, Finland). Active stimulation consists of delivering a constant current of 2 mA for 30 minutes per session, with the anode positioned over F3 (left dorsolateral prefrontal cortex) and the cathode over F4 (right dorsolateral prefrontal cortex) according to the international 10-20 EEG system. Participants receive 22 intensive sessions delivered five days per week, followed by 8 weekly maintenance sessions. For the sham condition, the same electrode placement and session duration are used; however, stimulation is applied only during a 30-second ramp-up and ramp-down period, with no sustained current delivered for the remainder of the session. This procedure is designed to maintain participant and assessor blinding.

Eligibility

Sex: ALLMin age: 60 YearsMax age: 75 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: 1. Right-handed (for MRI purposes) 2. Age 60 to 75 years 3. 6 years or more of schooling 4. Proficiency in Spanish 5. Amnestic Mild Cognitive Impairment established by clinical examination 6. Adequate visual and auditory acuity to perform neuropsychological tests and undergo cognitive rehabilitation 7. If receiving psychotropic medication, to have started it at least 12 weeks prior to the start of the study, remain at stable doses, or have discontinued it for at least 4 weeks 8. Good general health without medical or psychiatric illnesses that would interfere with the study 9. An informant capable of responding to clinimetric assessments throughout the study and willing to accompany the patient for at least 10 hours per week Exclusion Criteria: * 1\. Any neurological disease other than Alzheimer's disease that raises suspicion of cognitive impairment, such as Parkinson's disease, multiple infarct dementia, Huntington's disease, hydrocephalus, brain tumor, progressive supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, or a history of traumatic brain injury with loss of consciousness. 2\. Participants with a history of severe psychiatric disorders according to the DSM-5 (bipolar disorder, schizophrenia, chronic depression) or with psychotic features, agitation, or behavioral problems in the last three months that could lead to difficulties in complying with the protocol. 3\. History of psychoactive substance abuse and current alcohol consumption with a pattern of abuse or dependence in the last two years. 4\. Participants with abnormalities on a conventional electroencephalogram (paroxysmal phenomena identified by a neurophysiologist). 5. Participants with pacemakers, intracranial metallic objects or a history of brain surgery, aneurysm clips, artificial heart valves, ear implants, metal fragments or foreign objects in the eyes, skin or body. 5\. Participants with pacemakers, intracranial metallic objects or a history of brain surgery, aneurysm clips, artificial heart valves, ear implants, metal fragments, or foreign objects in the eyes, skin, or body. 6\. Participation in clinical studies with neuropsychological measures taken more than once a year. 7\. Having received prior treatment.

Outcomes

Primary Outcomes

Global cognitive function

Executive Function, Working Memory, Verbal Fluency, Episodic Memory, Planning, and Global Cognition Executive function will be assessed using the Five Digits Test (time/errors; lower = better; no fixed range). Verbal working memory will be measured with Digit Span (approx. 0-16 forward, 0-14 backward; higher = better) and visuospatial working memory with the Corsi Block-Tapping Test (span 2-9; higher = better). Verbal fluency will be assessed using phonemic fluency (letter F; no fixed range; higher = better). Episodic memory will be measured with the Hopkins Verbal Learning Test-Revised (HVLT-R; immediate recall 0-36, delayed recall 0-12; higher = better). Planning ability will be evaluated with the Tower of London (moves/time; lower = better; no fixed range). Global cognition will be assessed using the Montreal Cognitive Assessment (MoCA; 0-30; higher = better). \[Time Frame: Baseline, Week 5, Week 8, and Week 12\]

Time frame: Participants will undergo a 1-week baseline assessment, followed by a 5-week intensive intervention phase. A post-intervention assessment will be conducted at Week 6. Follow-up assessments will be performed at Weeks 10, 14, and 18. The total study durati

Secondary Outcomes

Calcium-related molecular biomarkers (STIM and ORAI gene expression)

Gene expression levels of STIM and ORAI will be measured from buccal swab samples using RT-PCR. Relative gene expression will be quantified (fold change). Changes in expression levels will be analyzed between groups, where increased or decreased expression reflects modulation of calcium-related pathways. \[Time Frame: Baseline, Week 5, Week 8, and Week 12\]

Time frame: Baseline (pre-intervention), post-intervention (after completion of the intensive phase, Week 5), and follow-up assessments (Weeks 8 and 12)