Abstract

Assessed as up to date: 2009/01/02

Background

Evidence from some, but not all non-randomised studies suggest the possibility that cognitive training may influence cognitive functioning in older people. Due to the differences among cognitive training interventions reported in the literature, giving a general overview of the current literature remains difficult.

Objectives

To systematically review the literature and summarize the effect of cognitive training interventions on various domains of cognitive function (ie memory, executive function, attention and speed) in healthy older people and in people with mild cognitive impairment.

Search strategy

The CDCIG Specialized Register was searched on 30 September 2007 for all years up to December 2005. The Cochrane Library, MEDLINE, EMBASE, PsycINFO and CINAHL were searched separately on 30 September 2007 to find trials with healthy people. These results were supplemented by searches from January 1970 to September 2007 in PsychInfo/Psyndex, ISI Web of Knowledge and PubMed.

Selection criteria

RCTs of interventions evaluating the effectiveness of cognitive training for healthy older people and people with mild cognitive impairment from 1970 to 2007 that met inclusion criteria were selected.

Data collection and analysis

Authors independently extracted data and assessed trial quality. Meta-analysis was performed when appropriate.

Main results

Only data on memory training could be pooled for analysis. Within this domain, training interventions were grouped according to several outcome variables. Results showed that for healthy older adults, immediate and delayed verbal recall improved significantly through training compared to a no-treatment control condition. We did not find any specific memory training effects though as the improvements observed did not exceed the improvement in the active control condition. For individuals with mild cognitive impairment, our analyses demonstrate the same pattern. Thus, there is currently little evidence on the effectiveness and specificity of memory interventions for healthy older adults and individuals with mild cognitive impairment.

Authors' conclusions

There is evidence that cognitive interventions do lead to performance gains but none of the effects observed could be attributable specifically to cognitive training, as the improvements observed did not exceed the improvement in active control conditions. This does not mean that longer, more intense or different interventions might not be effective, but that those which have been reported thus far have only limited effect. We therefore suggest more standardized study protocols in order to maximize comparability of studies and to maximize the possibility of data pooling - also in other cognitive domains than memory.

Author(s)

Martin Mike, Clare Linda, Altgassen Anne Mareike, Cameron Michelle H, Zehnder Franzisca

Summary

Effects of memory training in healthy older adults and older adults with mild cognitive impairment 

There is an increasing interest in information on the effectiveness of cognitive training interventions to improve memory in normal and mildly cognitively impaired older adults (60 years and older). We analyzed all cognitive interventions between 1970 and 2007 to determine their effectiveness. The results suggest that cognitive interventions do lead to performance improvements and that the size of the effects differs for different kinds of memory skills in healthy older adults and people with mild cognitive impairment. In particular, immediate and delayed verbal recall improved significantly through training compared to a no-treatment control condition but the improvements observed did not exceed the improvement in the active control conditions.

Reviewer's Conclusions

Implications for practice 

As the performance improvements observed did not exceed the improvement in active control conditions, we did not find any specific training effects for any of the abilities with sufficient data for the analysis. There is evidence that cognitive interventions targeting the improvement of memory in healthy older adults and people with mild cognitive impairment are effective in producing improvement in verbal immediate and delayed recall but that these cognitive training effects are not specific, i.e., alternative interventions (active controls) do just as well as training interventions in mild cognitive impairment. It remains an open question at this point if the heterogeneity of the populations tested or the quality of the interventions may have influenced the results and we can only speculate as to whether more intensive and longer training may be needed to achieve effects larger than in active control conditions.

Implications for research 

Our analyses provide surprisingly little evidence for the effectiveness and specificity of cognitive training interventions. Considering the sources of bias included that would typically lead to an overestimation of training effects, this argues against the effectiveness of cognitive training interventions. However, it may also suggest that future research needs to provide a more conclusive evidence base to make it possible to establish the effectiveness of cognitive interventions. First, a more standardized approach to examining the effectiveness of cognitive training is needed. Due to the heterogeneity of procedures, durations, intensities, methods of dealing with absent training participants, use of a variety of training contents, content combinations, and matching of evaluation instruments to training contents, the effects might be substantially larger if more similar studies could be pooled for the meta-analyses. Second, many training approaches include a combination of several elements, and trained individuals may respond quite differently to the different elements of the training. Thus, training effects on an individual level may be substantially higher than the group effects. Therefore, in future research, collapsing data within individuals before aggregating on a group level might provide more appropriate tests of the effectiveness of cognitive interventions. Third, there are clearly more studies reporting the effects on rather basic abilities such as free recall compared to more complex behaviours such as prospective memory or goal-setting. This is reasonable because improvements of basic abilities are prerequisite for transfer to more complex tasks which draw on a number of these basic abilities. The ability to adjust the use of cognitive skills to perform more complex tasks may be better captured by focusing on individual learning trajectories compared to focusing on mean level changes. Fourth, there are very few studies on the effectiveness of cognitive training interventions in individuals with mild cognitive impairment of any diagnostic kind. A consistent definition or agreement on few core criteria of mild cognitive impairment may help to gather evidence more quickly because a more widespread use of this definition would make this more likely a group of research interest. Variations in type and intensity of existing training interventions are needed to gain better knowledge about the efficacy of cognitive interventions in mild cognitive impairment.

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