Prevention of Alzheimer's Disease With CR Plus tDCS in Mild Cognitive Impairment and Depression (PACt-MD)

Summary

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Description

By the time Alzheimer's Dementia (AD) and related disorders (ADRD) are diagnosed the brain has sustained substantial insult that limits the efficacy of current treatments. Preventive interventions are urgently needed but prevention studies require large numbers of participants and long follow-up per...

By the time Alzheimer's Dementia (AD) and related disorders (ADRD) are diagnosed the brain has sustained substantial insult that limits the efficacy of current treatments. Preventive interventions are urgently needed but prevention studies require large numbers of participants and long follow-up periods unless they can target a high-risk population. The investigators propose to study the efficacy of a preventive intervention for AD in three high risk groups: (1) older persons with Mild Cognitive Impairment (MCI); (2) older persons with a major depressive disorder (MDD) without MCI; and (3) older persons with MDD and MCI. MCI is considered a prodromal condition for dementia with a progression rate of about 1% per month. MDD has independently been identified as one of the most promising targets for AD prevention studies since, even after successful treatment of their depressive episode, older persons with remitted MDD develop MCI or dementia at a rate of 1-2% per month. The investigators proposed intervention is a combination of cognitive remediation (CR) and non-invasive brain stimulation - transcranial Direct Current Stimulation (tDCS). Participants with MCI or MDD (with or without MCI) will be randomized to tDCS + CR or sham ("palcebo") tDCS + sham ("placebo") CR. Both CR and tDCS have been shown to induce neuroplasticity and improve cognition. The investigators hypothesize that their combination will enhance cognitive reserve and protect against cognitive decline and the onset of MCI in those with "normal" cognition or AD in those with MCI. The investigators design is informed by their experience conducting randomized controlled trials (RCTs) in older participants with dementia, MCI, or MDD over more than two decades. In the investigators recent donepezil prevention trial, combining donepezil with standard antidepressant maintenance prevented cognitive decline and the incidence of dementia in participants who had had both MDD and MCI. Building on this prevention trial, the investigators conceptualize the proposed study as a high-risk, high-gain RCT aimed at enhancing cognitive reserve and preventing cognitive decline and dementia in a high risk population. If the investigators are successful in this high risk population, then tDCS + CR can be tested in, and extended to, the general population (i.e., for universal prevention) or other groups at high risk for AD (i.e., for selective or indicated prevention). Five Toronto academic sites with a history of successful collaboration will consent up to a total of 500 participants meeting criteria for MCI (age 60 and older) or MDD (age 65 and older) to reach a target of 375 enrolled participants initiating the study intervention. Participants will be randomized to either: i) tDCS + CR or ii) sham tDCS + sham CR. They will first receive tDCS + CR (or sham + sham) 5 days a week for 8 weeks, followed by home-based CR (or sham) and booster sessions of tDCS + CR (or sham + sham) for 5 days every 6 months until they develop dementia (or MCI for those who are deemed cognitively intact at baseline) or complete the study. During the COVID-19 pandemic, the study has been modified to be administered in a hybrid manner to accommodate both in-person and virtual assessments. Clinical and cognitive assessments (every 12 months) can be done in person or remotely (via telephone or using WebEx/Zoom). Some assessments are modified to accommodate the change in format of administration while maintaining the validity and integrity of the data. The assessments that cannot be done via phone or videoconference will temporarily not be done. Similarly, the intervention booster group sessions (every 6 months) can also be provided in two formats of in-person or virtual (via WebEx or Zoom) sessions. The tDCS administration cannot be done remotely and hence the virtual booster sessions will only consist of the CR exercises.

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