Objective: To assess whether home-based, self-applied cognitive training combined with tDCS in older adults is feasible (primary), acceptable, and effective (secondary). Design: Monocentric, double-blind, randomized (1:1), controlled trial conducted from May 2021 to July 2023, involving six at-home sessions and pre-, post- and follow-up assessments in the laboratory. Setting: University Medicine Greifswald and homes of participants homes. Participants: Thirty older adults (60-80 years), randomized to anodal or sham tDCS group (n = 15 each). Interventions: Six sessions at home over the course of two weeks (three per week) with training of letter updating and concurrent self-applied tDCS (1.5 mA, 20 min/30 s). Participants were thoroughly trained in self-application of the stimulation and handling of the material. Main outcomes measures: The primary outcome was feasibility, operationalized by successfully performed interventional sessions per participant. Four or more out of six sessions successfully performed in at least 60% of all participants were defined for the trial to be deemed feasible. Secondary outcomes included: acceptability assessed via questionnaire and cognitive performance on training and transfer tasks. Results: 29 participants successfully completed four or more out of six intervention sessions (96.7%, 95%-CI: [81.9, 100.0]), confirming the feasibility of the intervention (primary outcome). Overall satisfaction with the intervention and mean feasibility rating was high (93%, 95%-CI: [77.6 to 99.2]). Training (letter updating) task performance was superior in the target compared to the control group (β = 3.5, 95%-CI: [0.5 to 6.6], p = 0.037). There was no substantial difference in the transfer (N-back) task (β = -5.1, 95%-CI: [-14.6 to 4.5], p = 0.23). Conclusions: Self-administered, home-based combination of cognitive training and tDCS is feasible and acceptable in older adults. Pre-defined secondary outcomes indicate superior cognitive enhancement of the trained function in the active stimulation group. Our study indicates that a Phase III trial is now warranted. Trial registration: Prospectively registered (clinicalTrials.gov, NCT04817124).

The authors have declared no competing interest.

NCT04817124

Funding for this study was provided by Bundesministerium fuer Bildung und Forschung (FKZ 01GQ1424A). This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) Project number 327654276, SFB 1315 to AF. CTLL is a PhD fellow funded by the Deutscher Akademischer Austauschdienst (DAAD) [scholarship: 91828451].

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics committee of the University Medicine Greifswald gave ethical approval of this work.

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I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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All data produced in the present study are available upon reasonable request to the authors.