The dynamic development of modern technologies raises questions as to the possibilities, benefits and limitations of their application among the older adults due to the developmental changes in the sensorimotor abilities, cognition and motivation observed in this age group (1). Although seniors proved to be late adapters to the world of modern technologies, the fact remains they effectively use those technologies for their own health protection and promotion, for instance telemedicine, e-health (2).
An important area for modern technologies application in older adults is improving their cognitive functioning through cognitive interventions (CI), including cognitive training (CT), cognitive stimulation (CS) and cognitive rehabilitation (CR) (3). As people get older, many cognitive abilities deteriorate and the process is referred to as cognitive ageing (4). It mostly affects memory processes, learning, attention, reasoning and executive functions (5, 6, 7). What is more, the risk of dementia disorders increases with age in the course of various neurodegenerative diseases (8, 9). Deterioration in cognitive functioning of an older adults results in their reduced independence, lower self-esteem and withdrawal from many areas of activity (professional, social and educational) due to deterioration in mental functions. In view of the above, studies into possible forms of non-pharmaceutical interventions aiming to maintain, improve or enhance cognitive performance, and prevent its deterioration in senior age gain particular relevance.
Research on the methods improving cognitive performance in cognitively healthy older adults and in persons with cognitive impairment, including dementia, have been conducted for many years now and have provided evidence of the effectiveness of various cognitive interventions (10).
For example, the meta-analysis of randomized controlled trials by Chiu and colleagues (11) indicated that CT is effective for non-demented older adults. Similarly, the review of research on CS and CT programs for healthy older participants performed by Tardif and Simard (12) pointed out that the results are promising for memory, attention, executive functions, and speed of processing. Also meta-analyses of the influence of process-based CT, like working memory or cognitive control training, in healthy older adults demonstrated the effectiveness of such CI (13, 14). Moreover, CT enhance stability of cognitive functioning across adulthood, as indicated the review by Eschen (15). According to this review all types of CT enhanced absolute stability of cognitive functioning, but the greatest effects were reported for process-based CT. What's more, findings of a few studies discussed in this review demonstrated that thanks to CT also the absolute stability in brain functioning across adulthood can increase. Also systematic review of randomised controlled trials with longitudinal follow-up revealed that CT can prevent the onset of dementia in healthy older adults (16). CT induced strong and persistent protective effects on longitudinal neuropsychological performance. Some studies considered in this review reported also transfer of training effects to general cognition and daily functioning.
Moreover, CI may be beneficial not only in normal ageing process, but also in the case of MCI. The results of all CI in cognitively healthy older adults and older adults with MCI between 1970 and 2007 reviewed by Martin et al. (17) suggest that CI lead to performance improvements and that the size of the effects differs for different kinds of memory skills in non-demented older adults and people with mild cognitive impairment (MCI). Systematic review of 10 studies, followed by effect sizes analysis found that CT (including cognitive exercises and memory strategies training) can produce moderate-to-large positive effects on memory-related outcomes in older adults with MCI (18). Positive influence of CI, including CT, on various aspects of memory, attention and executive functions in older adults with MCI was pointed out also in other review (19). Mewborn, Lindbergh and Stephen Miller (20) analysed 279 effects from 97 studies on CT in older adults. Overall, results indicated that CT produce a small, but significant, improvement in the cognitive functioning of older adults, relative to active and passive control groups. At the same time, cognitive status (cognitively healthy vs. MCI), as well as age and education were not significant moderators. Effects were larger for directly trained outcomes but were also significant for non-trained outcomes (i.e. transfer effect). However, not all reviews and meta-analyzes on the effects of CI in individuals with MCI lead to such optimistic conclusions. A meta-analysis on memory training effects pointed out the scarce of evidence of the effectiveness and specificity of such CT in older adults without cognitive impairment and with MCI (21).
Going further, the results of research on the possibility to improve cognitive functioning under the influence of CI in persons with dementia are less clear. Some reviews and meta-analyzes indicated positive effect of CI on cognitive functioning in dementia (22, 23, 24). Based on the analysis of randomized controlled trials, Ballard and colleagues concluded, that modest but significant benefits in the treatment of cognitive symptoms in people with Alzheimer’s disease (AD) can be achieved through various CI, including CT, CR and CS (25). Also the systematic review of the literature and meta-analysis of the effect of CT on multiple functional domains in AD patients showed medium effect sizes for learning, memory, executive functioning, activities of daily living, general cognitive problems, depression, and self-rated general functioning (26). According to the scoping review on the effects of non-pharmacological interventions for adults with mild cognitive impairment and early stage dementia, CI focused on remediation caused a little improvement in selected cognitive abilities, in turn cognitive training focused on compensation influenced the impact of cognitive changes impact on daily living (27). The effect sizes were however small. Moreover, most of the studies included in this review concerned MCI patients. The review comprised 20 studies in persons with MCI, only 8 studies in persons with early AD and 4 studies involved both, MCI and early AD patients. Other authors pointed out that convincing evidence of clinical significance for the impact of CI in cognitively impaired older adults was only obtained from single trials in terms of delay of cognitive decline, improvement in activities of daily living, or enhanced attainment of personally relevant goals (28). Furthermore, if CI types are distinguished, i.e. CT, CS and CR, it turns out that in people with dementia they vary in terms of effectiveness. Meta-analysis and meta-regression by Huntley and colleagues found the significant positive effect of CS on general cognitive functioning in dementia, but no evidence for the positive influence of CT or mixed approach, combining CT and CS (29). Also according to review by Bahar-Fuchs, Clare and Woods (30), CT is not associated with positive or negative effects on cognitive functioning in persons with mild to moderate dementia. In the review on CI in cognitively impaiered older adults authors firstly concluded that CI improve global cognitive functioning in patients with MCI or AD and their abilities of daily living, reduce behavioural disturbances, and have positive effects on quality of life. Secondly, authors noticed the varying effectiveness of particular types of CI, depending on the level of cognitive deficits. Patients with mild to moderate dementia benefited more from CS, while older adults with MCI from CT (31). It corresponds to the conclusions from the systematic review of 11 CT studies and 7 CS studies in individuals with dementia (32). In this review evidence for efficiency of CT among demented persons proved to be insufficient and doubtful. Contrary, for CS there was good evidence for general cognitive enhancement, more specifically in language and memory.
Currently, an increasing number of research concerns the efficacy of CI using modern technologies, like computerized cognitive training (CCT) or video games (VG). A systematic review on efficacy CCT for cognitively healthy older adult indicated that findings are comparable or better than those from reviews of more traditional, “paper-and-pencil” CT approaches (33). The authors concluded that computerized training may be an effective alternative. Lampit, et al. (34) reviewed the results of fifty-two studies on the effectiveness of CCT encompassing 4,885 healthy older adults. The overall effect size for CCT versus control was small but statistically significant. Small to moderate effect sizes were found for nonverbal memory, verbal memory, working memory, processing speed and visuospatial skills. No significant effects were found for executive functions and attention. According to the systematic literature review and meta-analysis by Tetlow and Edwards (35) commercially available CCT can improve cognitive abilities in older adults, who also report improvement on tasks relevant to their everyday lives. Other systematic review on clinical significance of commercially available computerized "brain training" programs was summarized by the authors' conclusion that at least some of such CT software is effective and can supporting healthy ageing (36). Moreover, Edwards et al. (37) conducted a systematic review and meta-analyses of Useful Field of View (UFOV) CT, and their results indicated that UFOV CT enhanced neural outcomes, speed of processing, and attention and showed far transfer to everyday functioning. UFOV CT effects were equivalent when compared to active- or no-contact control conditions. Moreover, improvements on the trained skills endured across ten years. Admittedly, they did not transfer to other neuropsychological outcomes, however positively enhanced well-being, health, and quality of life. A systematic review and meta-analysis on computer-based CI for people with dementia proved that these CI have moderate effects in cognition and mood but not on activities of daily living (38). A PRISMA-compliant network meta-analysis led to conclusion that in older adults with MCI and AD optimal intervention for cognitive performance is physical exercise, whereas CCT is the optimum for neuropsychiatric symptoms (39). This meta-analysis also showed that nonpharmacological therapies are better than pharmacological therapies in MCI and AD patients. Another meta-analysis concerned the efficacy of CCT in people with MCI or dementia indicated moderate overall effect on cognition in MCI and small to moderate effects for global cognition, attention, working memory, learning, and memory, with the exception of nonverbal memory (40). In turn in dementia, statistically significant effects were found on overall cognition and visuospatial skills, but the last ones were driven by trials of VR or VG. The authors concluded that CCT is efficacious in people with MCI but evidence for efficacy in people with dementia is weak and limited to trials of immersive technologies. The newest scoping review on non-immersive brain gaming for cognitively impaired older adults showed that most brain gaming interventions with the use of computer and/or touch screen led to improvement in at least one cognitive outcome (41). Going further, according to this review in older adults with MCI it was possible to get the near transfer effect by training in processing speed, memory, attention, and working memory, the far transfer effect by training in attention and working memory, and improvement in functional activities by training in visual processing speed and attention, or working memory. In turn, in older adults with dementia the supervised brain gaming training in memory, executive function, and language led to the near transfer effect. The conclusion of the authors points to the potential of brain gaming in the improvement of cognitive functioning in older adults with mild to severe cognitive decline. As regards VG, from a meta-analytic study on the enhancement of cognitive functioning in healthy older adults under influence of VG-based CT followed that such training induces positive changes in reaction time, attention, memory, and global cognition (42). The research by Wang, Zhu, Qi, Huang, and Li (43) proved that VG experiences may have a positive influence also on the brain activation underlying cognitive performance. Their results showed that healthy older VG players presented significantly better cognitive performance than non-VG players and greater brain activity, mainly in frontal-parietal areas.
Along with the intensive development of modern technologies, more and more advanced solutions are becoming available. In this context the use of VR in the CI is a new research area arousing growing interest. VR can be defined as “an advanced form of human-computer interface that allows the user to interact with and become immersed in a computer-generated environment in a naturalistic fashion” (44, p. 298). Currently the standard for fully immersive VR are head-mounted displays (HMDs) because they provide the greatest level of immersion. Besides HMD, VR can be implemented by world-fixed displays taking many forms, from a standard monitor to displays completely surrounding the user e.g., CAVEs, and hand-held displays, like smartphones or tablets (45, 46). Evidence is accumulating showing that VR-applications can successfully be employed for early detection and monitoring of physical and cognitive impairment (47, 48, 49, 50), but also for interventions in a wide range of medical conditions, like chronic pain, obesity, eating disorders, anxiety, phobia, depression, schizophrenia, autism, behavioural disorders and cognitive disorders of various etiologies (51, 52, 53, 54, 55, 56, 57).
One major benefit of VR-based CT is that it addresses previous criticisms about CCT by providing individuals with an intervention that is immersive, naturalistic, and mimics real-time and real-life, increasing ecologic validity (54, 58, 59, 60). Ecological validity provided by VR can be seen as a key component for assessing and training cognitive skills that are relevant for functional tasks in real-world contexts (61, 62, 63).
Moreover, it is worth to be noted that VR applications like VG and CCT create favourable conditions to implement the rules of so called serious games in CT for older adults (64, 65). Serious games have been used in the ﬁeld of neurodegenerative disorders such as Alzheimer’s disease to support and improve the assessment of different functional and cognitive abilities, and to provide alternative solutions for patients’ rehabilitation. Results confirmed that SG are also adapted to older people with MCI (66).
In summary, currently VR technology is considered as one of the most promising tools for providing nonpharmacological cognitive interventions for cognitively healthy older adults and persons with different level of cognitive impairment (54, 67).
Nevertheless, research on the effectiveness of VR-based CT is still scarce, all the more so in the group of older adults and in relation to cognitive ageing. For example in the systematic review of VR applications in inpatient medical settings between 2005 and 2015, only one of 11 studies included in the review concerned cognitive rehabilitation. This study was however not focused on cognitive ageing. It involved 18 patients with traumatic brain injury, aged 19–73 years (51).
The efficacy of CCT and VR-based CT in older adults with MCI or dementia was assessed in systematic review by Coyle, Traynor and Solowij (68). The cognitive domains of attention, executive function, and memory (visual and verbal) showed the most consistent improvements, including long-term effects. CCT and VR-based CT were however moderately effective in long-term improvement of cognition for those at high risk of cognitive decline and did not improve the activity of daily living. It should be noted that only three studies using VR-based CT were taken into account in the systematic review, although the authors pointed out that the review was undertaken following a wide search of the available literature on the topic area. It indicates the small number of studies carried out so far on this topic.
Recently, several studies have been published, the results of which are generally promising. However, the study samples are usually small, including case studies and articles describe pilot studies or even the research plan with only partial results from initial phases of the study which are continued (61, 69, 70, 71). It is recommended that research into possible applications of VR in CI shall be conducted because of the preliminary nature of most data currently available in this area and a relatively small number of studies carried out so far (54, 68).