The objective of this study is to determine the effects of a 6-month, home-based personalized transcranial direct current stimulation (tDCS) intervention targeting the left dorsolateral prefrontal cortex on cognitive function, dual task standing and walking, and other metrics of mobility in older adults with motoric cognitive risk syndrome (MCR).

In older adults, motoric cognitive risk (MCR) is a pre-dementia transition state between "normal" aging and dementia. MCR is associated with impaired function within several brain networks that causes numerous symptoms including loss of memory, the ability to complete complex mental tasks, and the capacity to control one's walking and thus avoid falling and fall-related injuries. This study seeks to assess the short-term and long-term use of an investigational device called a transcranial direct current stimulation (tDCS).

tDCS is a noninvasive technology that enables selective modulation of brain network function, to provide multi-symptom relief to older adults with MCR. By using state-of-the-art technology to 1) utilize a personalized tDCS intervention via an established optimization approach using individual brain MRIs, and 2) complete stimulation in a home-based setting, this study is expected to result in the development of tDCS interventions that have maximal impact on daily life function within this population.

In this study, investigators will conduct a 9-month sham-controlled, double-blinded, multi-site trial in 128 older adults aged 65-90 years old with MCR. All enrolled participants will complete an open-label 2-week, 10-session tDCS intervention. During the open-label phase of the study, all participants will receive active tDCS. Then, participants will be randomly assigned into either the tDCS arm that receives five weekly tDCS sessions for 6 months, or a combination arm of five weekly tDCS sessions for 3 months before or after five weekly sessions of sham for 3 months. Sham treatment is similar to the study tDCS treatment, but omits the key therapeutic element of the treatment being studied. Participants in the combination arm will not know whether they are receiving tDCS or sham during the first or second 3-month period. Enrolled participants will complete assessments relating to cognition, mood, balance, and memory at baseline, after the 2-week open-label phase, after 3 and 6 months of tDCS, and again 3 months later. Once a week, participants will also complete a gait (walking) assessment at home. MRI scans will be performed at baseline and after completing 3 months of tDCS.

Inclusion Criteria:

• Men and women
• Age 65-90 years
• Subjective cognitive complaints as defined by a 'Yes' response to "Do you feel that you have more problems with memory than most?" or a 'No' response to "is your mind as clear as it used to be?"
• Montreal Cognitive Assessment (MoCA) score ≥21
• Slow gait speed as measured by averaging two 4-Meter walks and defined as a usual walking speed one standard deviation below age and sex-adjusted means.
• Absence of significant disability as defined by the ability to walk over the instrumented gait mat unassisted (e.g., able to walk without any walking aids for at least 2 minutes non-stop) and preserved activities of daily living as defined by a score of less than 9 on the Functional Activities Questionnaire.
• Identification of an eligible informant
• Identification of a willing and able tDCS-administrator; i.e., a study partner to lead the administration of home-based transcranial direct current stimulation (tDCS)
• Access to reliable WiFi in the participant's home

Exclusion Criteria:

• Formal education less than the 8th grade
• Previous physician diagnosis of dementia
• Any current diagnosis of a major psychiatric disorder (e.g., schizophrenia, bipolar disorder, major depressive disorder)
• Evidence of moderate-to-severe depressive symptoms defined by a score of ≥9 on the 15-item Geriatric Depression Scale
• History of head trauma resulting in prolonged loss of consciousness
• History of fainting spells of unknown or undetermined etiology that might constitute seizures
• History of seizures, diagnosis of epilepsy, or immediate (first-degree relative) family history of epilepsy except for a single seizure of benign etiology (e.g. febrile seizures) in the judgment of a board-certified neurologist
• Hospitalization within the past three months due to acute illness, or as the result of a musculoskeletal injury significantly affecting gait or balance
• Any unstable medical condition or chronic (particularly) uncontrolled medical conditions that may cause a medical emergency in case of a provoked seizure (cardiac malformation, cardiac dysrhythmia, asthma, etc.) or study complication
• Substance use disorders within the past six months
• A hairstyle or headdress that prevents electrode contact with the scalp or would interfere with the stimulation (for example thick braids, hair weave, afro, wig)
• Chronic vertigo
• Myocardial infarction within the past 6 months
• Active cancer for which chemo-/radiation therapy is being received
• Legal blindness
• Visual hallucinations (history or self-report)
• Pacemaker
• Contraindications to MRI or tDCS, including unprovoked seizure within the past two years, risk of ferromagnetic objects anywhere in the body, self-reported presence of specific implanted medical devices (e.g., deep brain stimulator, medication infusion pump, cochlear implant, pacemaker, etc.), the presence of any active dermatological condition, such as eczema, on the scalp, etc. as outlined by current recommendations for noninvasive brain stimulation endorsed by the International Federation for Clinical Neurophysiology.
• History of REM sleep behavior disorder (RBD), often an early sign of Parkinson's disease
• Medications and medical history will be reviewed by the responsible covering physician and a decision about inclusion will be made based on the participant's past medical history, drug dose, history of recent medication changes or duration of treatment, and combination with other CNS active drugs.

De-identified demographic, cognitive, motor, clinical, gait kinematics, free-living accelerometry, functional near infrared spectroscopy (fNIRS), MRI, and trial compliance and safety data

Sharing of clinical trial data (participant level and summary level data, raw and processed) is expected at the time of publication of the primary results or within 9 months of database lock, whichever comes first. At minimum, per HSL's Record Management, Retention, Disposition and Destruction Policy, all data will be retained for at least seven years after project completion or the sponsored award agreement end date as stipulated in its terms and conditions.

De-identified data and all metadata will be archived within the Marcus Institute Data Archiving Service (MIDAS), a publicly accessible website built on the CKAN (Comprehensive Knowledge Archive Network) open-source data management platform. The MIDAS system is maintained and hosted by Hebrew SeniorLife.

Access to scientific data will be controlled prior to publication of the primary results or for 9 months following database lock, whichever comes first. During this period, the project PI will maintain and chair a standing subcommittee of the project investigators which will review each request. Upon majority approval of a request, access to the data may be granted in secure fashion. After this period, archived data will be accessible by investigators without need of approval by the study team. Moreover, investigators who wish to access data will not need to be affiliated with HSL. Data containing patient identifiers or related sensitive fields will be archived on HSL private servers.

Study personnel administering assessments, caregivers administering tDCS and the participants will not be aware of tDCS intervention arm assignment. The investigators will ensure double-blinding by programming the tDCS software with intervention-specific stimulation codes, as supplied by personnel uninvolved in data collection prior to study initiation.