This study aims to evaluate the feasibility, acceptability, and preliminary effects of a home-based, remotely supervised intervention combining transcranial direct current stimulation (tDCS) and online chair yoga (OCY) to manage chronic knee pain in older adults with Alzheimer's Disease and Related Dementias (ADRD). Chronic knee pain is prevalent among individuals with ADRD and is often underdiagnosed and undertreated, contributing to neuropsychiatric symptoms, reduced quality of life, and increased caregiver burden. Current pharmacological options, such as opioids, pose risks of adverse events in this population.

tDCS is a safe, noninvasive technique that uses low-intensity electrical current to modulate brain activity and may improve pain perception by targeting central mechanisms. Chair yoga is a mind-body intervention shown to improve pain and mood in older adults, including those with dementia. This study proposes that combining tDCS and OCY may have synergistic benefits in reducing pain and enhancing function.

Participants will include older adults aged 60+ with mild to moderate ADRD and chronic knee pain, along with their caregivers. Over four weeks, participants will complete 14 supervised sessions of combined tDCS and OCY at home. Outcomes include feasibility, satisfaction, pain intensity, pain interference, neuropsychiatric symptoms, sleep disturbance, cognitive function, mobility, and quality of life. Neurophysiological measures (e.g., fNIRS, EEG, HF-HRV) will also be assessed to explore underlying mechanisms.

This study seeks to lay the foundation for future large-scale randomized controlled trials of home-based nonpharmacological interventions for chronic pain in ADRD.

Older adults with ADRD frequently experience chronic pain, particularly knee pain, which is associated with worse behavioral symptoms and faster cognitive decline. Despite its impact, pain is often inadequately treated in this population due to communication difficulties and the risks associated with pharmacological treatments, especially opioids.

Transcranial direct current stimulation (tDCS) is a promising nonpharmacological therapy that delivers low-intensity electrical current to modulate cortical excitability. Research suggests that tDCS can reduce clinical and experimental pain and improve pain processing, particularly when targeted to the motor cortex. Our group has demonstrated the safety and efficacy of home-based, remotely supervised tDCS in older adults, including those with ADRD.

Chair yoga (CY), a modified yoga intervention involving seated or chair-supported postures, is also safe and effective for older adults with chronic pain and cognitive impairment. CY has demonstrated benefits in reducing pain, improving mood, and promoting physical activity with minimal risk of falls. Evidence suggests that yoga interventions may enhance central pain modulation and reduce neuropsychiatric symptoms.

This pilot study tests a novel combination of tDCS and online CY (OCY) in a home-based setting. We hypothesize that combining tDCS and OCY will reduce chronic knee pain and improve related symptoms in older adults with ADRD.

Participants will be recruited from geriatric outpatient clinics and community settings. Eligible participants will be 60 years or older, have mild to moderate ADRD, and experience chronic knee pain. The intervention will include 14 sessions over four weeks. All sessions will be supervised remotely via a secure videoconferencing platform.

Primary outcomes are feasibility, acceptability, and satisfaction, assessed through recruitment, adherence, dropout rates, and participant feedback. Secondary outcomes include reductions in knee pain (measured by Numerical Rating Scale and MOBID-2), pain interference (PROMIS Pain Interference 4a), sleep disturbance (ActiGraph), neuropsychiatric symptoms (Neuropsychiatric Inventory Questionnaire), cognitive function (Montreal Cognitive Assessment and Cognivue), mobility (Timed Up and Go), and quality of life (QOL-AD).

Exploratory neurophysiological outcomes will include functional near-infrared spectroscopy (fNIRS) to assess pain-related brain activity, EEG for neural pain signatures, and high-frequency heart rate variability (HF-HRV) for autonomic function.

This study will help determine the feasibility and potential effects of a scalable, home-based tDCS+OCY protocol, with the goal of informing future large-scale trials and advancing personalized, nonpharmacological pain care in ADRD.

Inclusion Criteria (participants):

• Live in the community (not institutionalized).
• Have a diagnosis of Alzheimer's disease and related dementias (ADRD), including Alzheimer's disease, Lewy Body Dementia, Vascular Dementia, or Multiple Etiology Dementias (MED) diagnosed by a neurologist or other healthcare provider.
• Be in mild to moderate ADRD, as indicated by a Quick Dementia Rating Scale (QDRS) score between 6 and 20.5.
• Score above 10 on the Montreal Cognitive Assessment (MoCA).
• Experience chronic knee pain (caregiver-reported average pain in the past 3 months > 40 out of 100).
• Have no planned changes to their medication regimen or other interventions for knee pain during the trial.
• Agree to participate in both transcranial direct current stimulation (tDCS) and online chair yoga (OCY).
• Be able to ambulate independently with minimal assistance (e.g., using a cane or walker) for participation in OCY and the Timed Up and Go (TUG) test. - -- Be English-speaking and able to understand verbal instructions (literacy not required).
• Be able to consent for themselves or identify a legally authorized representative who can provide written informed consent.
• Exhibit neuropsychiatric symptoms (e.g., apathy, agitation).
• Be naïve to yoga and tDCS.

Exclusion Criteria (participants):

• a history of brain surgery, brain tumor, head trauma, seizure/epilepsy, stroke, cancer affecting the head, or intracranial metal implantation;
• systemic rheumatic disorders, including rheumatoid arthritis, systemic lupus erythematosus, or fibromyalgia;
• prosthetic knee replacement or non-arthroscopic surgery to the affected knee;
• compromised skin integrity on the head in the area where electrodes will be placed;
• serious comorbidities that preclude participation in tDCS or OCY (e.g., heart failure [level IV] causing shortness of breath on exertion);
• hospitalization within the preceding year for neuropsychiatric illness that would impact knee pain or interfere with study procedures;
• use of another neurostimulation device (e.g., spinal cord stimulator, cardio-stimulator, or implanted cardioverter-defibrillator).

Inclusion Criteria (caregivers):

A caregiver is defined in this study as the person who provides care and assistance to a patient with ADRD (e.g., helping with daily activities, managing medications, ensuring safety).

• Caregivers must be at least 18 years old
• have provided care and assistance to the patient for at least 10 hours per week at the time of enrollment
• anticipate continuing to provide care and assistance for the next 4 months (until the study ends)
• be willing to receive tDCS training, administer home-based tDCS sessions, and assist the patient in attending OCY sessions
• have access to a reliable Internet connec¬tion for secure videoconferencing for real-time remote supervision
• English-speaking caregivers who can understand verbal instructions.

Exclusion Criteria (caregivers):

• alcohol/substance use disorder
• inability to understand English
• disability that would prevent assisting patients with ADRD from participating in tDCS and OCY (e.g., blindness, deafness)
• unwillingness to provide care and assistance to patients until the study is completed.
• If caregiver does not meet the inclusion/exclusion criteria, the participant will not be accepted into the study.

IPD will be stored securely electronically via redCAP and physically in locked cabinets within the lab. There is no plan to share IPD with other researchers.