The terms 'cognition' and 'cognitive function' describe all the mental activities related to thinking, learning, remembering, and communicating. Normal changes in cognition become evident with aging. Also, diseases may affect cognition, principally dementia, which becomes increasingly common with increasing age from about 65 years onwards. Researchers have shown a great deal of interest in trying to prevent cognitive decline and dementia. It is known that being mentally active throughout life is associated with lower risk of dementia. Therefore, it is has been suggested that encouraging mental activity in midlife (which we define in this review as 40 to 65 years of age) might be an effective way of maintaining good cognitive function as people age. Cognitive training involves a set of standardised tasks intended to 'exercise the brain' in various ways. Programmes of cognitive training are often delivered by way of computers or mobile technology so that people can perform activities on their own at home. Increasingly, these are provided in commercial packages that are advertised to the general public. We wanted to know whether computerised cognitive training is an effective way for people between 40 and 65 years of age to maintain good cognitive function as they age.
What we did
We searched the medical literature up to 15 March 2018 for trials that compared the cognitive function of people 40 to 65 years of age who had taken part in computerised cognitive training lasting at least three months versus a control group that had not done so. For the comparison to be as fair as possible, it should have been decided randomly whether participants were assigned to the cognitive training group or the control group. We were primarily interested in overall measures of cognition. The choice of three months of intervention was somewhat arbitrary, but we thought it unlikely that shorter periods of training could have long-lasting effects.
What we found
We found that a lot of shorter studies had been conducted, but only one study met our criteria for this review. It took place in the UK and included two different types of online cognitive training. The control group participated in an online game that was not expected to have cognitive effects. This training lasted six months, and study authors measured cognition at the end of the training period. Resarchers randomised 6742 people in the study, but the dropout rate was high. We thought this put the results at high risk of bias; therefore we considered the quality of evidence provided by this study to be low, meaning that further research might well lead to different results. This study did not measure overall cognitive functioning - which we were most interested in - but it did measure some subtypes of cognitive function. The cognitive training group did slightly better on a test of reasoning, and the control group did very slightly better on a test of working memory, which is a very short-term type of memory. No evidence suggested that the groups differed in memory measured by a word-learning test.
We were not able to tell whether taking part in computerised cognitive training in midlife has any lasting effects on cognitive function. We think this is an important question that should be investigated further in trials that test cognitive training over three months or longer. It will also be important for researchers to try to find the best ways to keep people motivated to persist with training.
We found low-quality evidence from only one study. We are unable to determine whether computerised cognitive training is effective in maintaining global cognitive function among healthy adults in midlife. We strongly recommend that high-quality studies be undertaken to investigate the effectiveness and acceptability of cognitive training in midlife, using interventions that last long enough that they may have enduring effects on cognitive and brain reserve, and with investigators following up long enough to assess effects on clinically important outcomes in later life.
Normal aging is associated with changes in cognitive function that are non-pathological and are not necessarily indicative of future neurocognitive disease. Low cognitive and brain reserve and limited cognitive stimulation are associated with increased risk of dementia. Emerging evidence now suggests that subtle cognitive changes, detectable years before criteria for mild cognitive impairment are met, may be predictive of future dementia. Important for intervention and reduction in disease risk, research also suggests that engaging in stimulating mental activity throughout adulthood builds cognitive and brain reserve and reduces dementia risk. Therefore, midlife (defined here as 40 to 65 years) may be a suitable time to introduce cognitive interventions for maintaining cognitive function and, in the longer term, possibly preventing or delaying the onset of clinical dementia.
To evaluate the effects of computerised cognitive training interventions lasting at least 12 weeks for maintaining or improving cognitive function in cognitively healthy people in midlife.
We searched up to 31 March 2018 in ALOIS (www.medicine.ox.ac.uk/alois), the specialised register of the Cochrane Dementia and Cognitive Improvement Group (CDCIG). We ran additional searches in MEDLINE, Embase, PsycINFO, CINAHL, ClinicalTrials.gov, and the WHO Portal/ICTRP at www.apps.who.int/trialsearch, to ensure that the search was as comprehensive and as up-to-date as possible, to identify published, unpublished, and ongoing trials.
We included randomised controlled trials (RCTs) or quasi-RCTs, published or unpublished, reported in any language. Participants were cognitively healthy people between 40 and 65 years of age (80% of study population within this age range). Experimental interventions adhered to the following criteria: intervention was any form of interactive computerised cognitive intervention - including computer exercises, computer games, mobile devices, gaming console, and virtual reality - that involved repeated practice on standardised exercises of specified cognitive domain(s) for the purpose of enhancing cognitive function; duration of the intervention was at least 12 weeks; cognitive outcomes were measured; and cognitive training interventions were compared with active or inactive control interventions.
For preliminary screening of search results, we used a 'crowd' method to identify RCTs. At least two review authors working independently screened remaining citations against inclusion criteria; independently extracted data; and assessed the quality of the included trial, using the Cochrane risk of bias assessment tool. We used GRADE to describe the overall quality of the evidence.
We identified one eligible study that examined the effect of computerised cognitive training (CCT) in 6742 participants over 50 years of age, with training and follow-up duration of six months. We considered the study to be at high risk of attrition bias and the overall quality of the evidence to be low.
Researchers provided no data on our primary outcome. Results indicate that there may be a small advantage for the CCT group for executive function (mean difference (MD) -1.57, 95% confidence interval (CI) -1.85 to -1.29; participants = 3994; low-quality evidence) and a very small advantage for the control group for working memory (MD 0.09, 95% CI 0.03 to 0.15; participants = 5831; low-quality evidence). The intervention may have had little or no effect on episodic memory (MD -0.03, 95% CI -0.10 to 0.04; participants = 3090; low-quality evidence).