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A Systematic Review and Meta-Analysis of Transcranial Direct Current Stimulation to Remediate Age-Related Cognitive Decline in Healthy Older Adults

Authors Indahlastari A, Hardcastle C, Albizu A, Alvarez-Alvarado S, Boutzoukas EM, Evangelista ND, Hausman HK, Kraft J, Langer K, Woods AJ

Received 18 November 2020

Accepted for publication 11 March 2021

Published 29 March 2021 Volume 2021:17 Pages 971—990


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 5

Editor who approved publication: Dr Roger Pinder

Aprinda Indahlastari,1,2 Cheshire Hardcastle,1,2 Alejandro Albizu,1,3 Stacey Alvarez-Alvarado,1,2 Emanuel M Boutzoukas,1,2 Nicole D Evangelista,1,2 Hanna K Hausman,1,2 Jessica Kraft,1,3 Kailey Langer,1,2 Adam J Woods1– 3

1Center for Cognitive Aging and Memory, McKnight Brain Institute, University of Florida, Gainesville, FL, USA; 2Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, USA; 3Department of Neuroscience, University of Florida, Gainesville, FL, USA

Correspondence: Aprinda Indahlastari
Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, USA
Tel +1 352-294-5842
Email [email protected]

Background: Transcranial direct current stimulation (tDCS) has been proposed as a possible method for remediating age-associated cognitive decline in the older adult population. While tDCS has shown potential for improving cognitive functions in healthy older adults, stimulation outcomes on various cognitive domains have been mixed.
Methods: A systematic search was performed in four databases: PubMed, EMBASE, Web of Science, and PsychInfo. Search results were then screened for eligibility based on inclusion/exclusion criteria to only include studies where tDCS was applied to improve cognition in healthy older adults 65 years and above. Eligible studies were reviewed and demographic characteristics, tDCS dose parameters, study procedures, and cognitive outcomes were extracted. Reported effect sizes for active compared to sham group in representative cognitive domain were converted to Hedges’ g.
Main Results: A total of thirteen studies involving healthy older adults (n=532, mean age=71.2+ 5.3 years) were included in the meta-analysis. The majority of included studies (94%) targeted the prefrontal cortex with stimulation intensity 1– 2 mA using various electrode placements with anodes near the frontal region. Across all studies, we found Hedges’ g values ranged from − 0.31 to 1.85 as reported group effect sizes of active stimulation compared to sham.
Conclusion: While observed outcomes varied, overall findings indicated promising effects of tDCS to remediate cognitive aging and thus deserves further exploration. Future characterization of inter-individual variability in tDCS dose response and applications in larger cohorts are warranted to further validate benefits of tDCS for cognition in healthy older adults.

Keywords: tES, tDCS, aging, cognitive decline

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