To the best of our knowledge, this is the first randomized, controlled study to compare multi-domain with single-domain CogTr intervention in community-living healthy older people. Immediate and long-term follow-up provided powerful proof for the improvement and maintenance of training-related effects on cognitive function.
The data presented here demonstrated that: (1) cognitive function varied along with time. RBANS total score, index scores and the visual reasoning test showed that the change in cognitive outcomes varied with time due to different group design and that each group benefitted differently after CogTr. CogTr was effective in improving test-related cognitive functions. (2) Multi-domain CogTr produced a significant effect on the RBANS total score, the visual reasoning test and immediate and delayed memory indices, while single-domain CogTr showed improvement in RBANS total score, the visual reasoning test, delayed memory and visuospatial/constructional index score, and CWST word interference. These results demonstrated that both multi-domain and single-domain CogTr resulted in training-related effects in cognitive improvement. Multi-domain CogTr resulted in better improvement in memory ability, while single-domain training gave better results for visuospatial/constructional and attention ability. (3) Besides the visual reasoning test, single-domain CogTr revealed effective improvement on the RBANS total score, delayed memory, visuospatial/constructional abilities, language, and CWST word interference. These results showed the generalization of benefit to non-trained cognitive functions, and such benefits persist. (4) It is notable that the RBANS total score, delayed memory and the visual reasoning test showed significant training effects in the multi-domain CogTr group at the 12-month posttest, while the single-domain CogTr only showed training effect on CWST word interfere at the 12-month posttest. The multi-domain CogTr effect showed better performance than single-domain CogTr at long-term follow-up and resulted in a steady gradual increase after intervention in most measure outcomes. These results proved that multi-domain CogTr had a better training effect on maintenance. (5) Booster training had a significant effect on the RBANS total score, the visual reasoning test, the completion time of TMT, and the visuospatial/constructional index score. These results prove that booster training was effective and enhanced the initial training effect on reasoning, and executive and visuospatial/constructional ability. (6) Reasoning ability showed a good training effect in both intervention groups and had no significant group differences at immediate and 6-month follow-up. Meanwhile, the multi-domain group showed better performance at the 12-month follow-up, which was consistent with the training effect maintenance on other cognitive tests. Furthermore, booster training also had a significant effect on the visual reasoning test. These results indicate that reasoning ability may be the domain most sensitive to CogTr (7). The completed training group outperformed the partial training group on visuospatial/constructional, reasoning, attention and processing speed abilities. These results also proved that cognitive training was effective.
Compared to previous studies on CogTr in healthy older adults [2
], our study drew some similar conclusions. First, CogTr in healthy older people produced positive effects. CogTr helped normal older people perform better on a series of measures of specific cognitive abilities. Effect sizes of cognitive abilities posttest are mostly consistent with previous research [2
]. Second, CogTr can result in a generalization of the training effect since untargeted cognitive domains also showed a better performance after single-domain CogTr and the effect was maintained [2
]. Beneficial effects of CogTr were limited not only to trained functions but extended to other cognitive abilities. Third, booster sessions consolidated the effects of initial training [2
], although the effects were limited to reasoning, visuospatial/constructional abilities and faster processing.
Some important findings are described in this study for the first time. First of all, the comparison between multi-domain and single-domain CogTr with healthy older adults found that certain domains benefit differently from CogTr. Memory ability benefits more from multi-domain CogTr, while visuospatial/constructional and attention abilities benefit more from single-domain CogTr. Furthermore, although the CogTr impact on cognitive function decreased over time, it remained statistically significant, attesting to the durability of the intervention effects. Multi-domain CogTr has more advantages for effect maintenance. Secondly, the largest effect was observed in reasoning ability. The NES of initial training and booster training were larger than the values showed in the ACTIVE study [2
]. The difference may be due to more training sessions (24 versus 10) in our study. Thus, we concluded that reasoning ability may be the domain that is most sensitive to CogTr.
It is interesting that the single domain training, which focused on reasoning, outperformed multi-domain in other cognitive domains but not in the reasoning domain. Why did single-domain training outperform multi-domain training in other cognitive domains? The reason might be the generalization of the training effect. Several studies have proved that non-trained cognitive domains could also be improved after single-domain training [43
]. The reason why multi-domain training outperformed single domain training in the reasoning domain may be that reasoning, as an important mental process, needs to collaborate with other brain processes. Single-domain CogTr usually doesn't consider the elaborate collaboration with other mental processes, which is necessary to create and maintain a viable healthy mind capable of flexibility in thinking, recalling, linking, and reacting to one's world [24
]. Thus, multi-domain training may have more advantages than single-domain training because of the collaboration.
One limitation of this study is that 53 subjects drop out before completing the baseline cognitive testing due to the following reasons. First, there was a long time lag between randomization and baseline assessment, therefore, some older adults had totally forgotten our study or changed their contact information. Second, the baseline assessment was conducted in summer. Some older adults refused to attend the assessment due to the hot weather. Third, all subjects in our study came from three communities in Shanghai, which could not be fully representative of the entire population of non-demented older people in China. This may cause bias in our study and limit the generalization of our results. We may need to select multiple cities for recruitment in the future to avoid this bias. Whether our conclusions could be applied to other populations deserves to be further studied. Although the limitations exist, this study represents an important extension of previous knowledge of the effects of CogTr on brain aging. Several cognitive domains, such as memory, visual reasoning, visuospatial/constructional and attention improved significantly after CogTr. More importantly, such benefits were maintained over time. The clinical role of CogTr with healthy individuals was primary prevention to reduce disease incidence [6
]. Decline in cognitive abilities has been shown to lead to an increased risk of functional difficulty in independent living [39
]. There was evidence that improvements in cognitive function can have a positive effect on daily functioning [39
]. The generalization of the training effect on daily functioning has also been seen in several studies [45
Thus, CogTr not only can improve cognition but may also have positive effects on daily functioning. CogTr, which produces no toxic effects, deserves to be further studied for its possible preventive and palliative therapeutic value. With acceptable compliance and training benefits and reasonable cost of implementation, our study may encourage future use of these CogTr methods to improve or maintain cognitive and daily function in cognitively impaired older adults.