Efficacy of cognitive training on executive functions in healthy older adults: a systematic review with meta-analysis of randomized controlled trials

AbstractObjective Systematically review randomized controlled trials on the efficacy of cognitive training on executive functions in healthy older people.Measures The outcome measures were related to inhibitory control, working memory, and cognitive flexibility.Results Thirty-one trials were included in the systematic review and thirteen trials in the meta-analysis. In the overall analysis, the cognitive training enhanced inhibitory control when measured by the Stroop task (p < .001, d = 1.64) and working memory when measured by the Corsi Block task (p = .002, d = .16). A marginal significance was found for working memory in the Digit Span task – Forward (p = .06, d = .92). However, cognitive training did not enhance inhibitory control when measured by the Go/No-Go task (p = .76, d = .59), working memory when measured by the Digit Span – Backward (p = .72, d = .95) and N-Back (p = .10, d = .26) tasks, and cognitive flexibility when measured by Trail Making – Part B (p = .08, d = .27) and Semantic Fluency (p = .49, d = .06) tasks.Conclusion Mixed evidence was found for inhibitory control and working memory; cognitive flexibility showed no evidence of improvement.Keywords: Older adultsmeta-analysiscognitive agingcognitive trainingexecutive functions AcknowledgementsThe authors would like to thank the editor and three anonymous reviewers who provided valuable suggestions which improved the quality of the present study.Disclosure statementNo potential conflict of interest was reported by the author(s).Data availability statementSearch strategy, data obtained from databases and directories, data extracted for meta-analysis, and outputs of all analyses are available at https://osf.io/64xmj/.Notes1 A passive control group refers to protocol with no intervention between pre- and post-testing (i.e. no-contact control group). An active control group refers to protocol with an intervention, ideally with similar topography of the experimental group's intervention, but planned to promote no enhancement in the cognitive processes of interest that is evaluated in the pre- and post-testing (e.g. playing Sudoku when the experimental intervention seeks to promote gains in inhibitory control) in order to control placebo-like effects of the cognitive training.2 The Stroop task assesses the ability to inhibit cognitive interference, which occurs when the processing of a stimulus feature simultaneously affects the processing of another attribute of the same stimulus (Scarpina & Tagini, Citation2017). The Go/No-Go task involves a series of decisions in which participants are asked to respond to one class of stimuli, that is, the go stimuli, but not to another class of stimuli, that is, the no-go stimuli (Young et al., Citation2018). The Digit Span task involves reading out a series of strings of digits to the participants who are required to repeat them in the same or reverse order of presentation (i.e. forward and backward conditions; Tripathi et al., Citation2019). In the N-Back task participants are presented a series of visual stimuli and they are asked for each stimulus whether it matches a stimulus n positions before, which requires maintaining continuous updating and processing of information (Gajewski et al., Citation2018). The Corsi Block consists of a surface of scattered blocks in which the examiner taps a sequence of blocks and the participant has to repeat the sequence in the same order or backwards (Kessels et al., Citation2000). In the Trail Making – Part B, subjects connect 25 encircled numbers and letters in numerical and alphabetical order, alternating between numbers and letters (Linari et al., Citation2022). In the Semantic Fluency tasks the individuals are required to recall items. Some variations of this test include the fluency of certain classes of words or different semantic categories such as animals and fruits (Lopes et al., Citation2009).3 From the total of 5 trials that entered the N-Back task meta-analysis, two used pictorial stimuli instead of verbal stimuli (Jaeggi et al., Citation2020; Kazazi et al., Citation2021). Both trials compared the cognitive training to passive controls and account for a small treatment effect (SMD = .32).Additional informationFundingThis work was supported by the Federal District Research Support Foundation – FAPDF, Brazil [Master's scholarship under Edict n. 0005/2022] and National Council for Scientific and Technological Development – CNPq, Brazil [undergraduate scientific initiation scholarship under Edict ProIC/DPG/UnB 2021/2022].