Are cognitive interventions effective in Alzheimer’s disease? A controlled meta-analysis of the effects of bias.

Abstract

Objective: There is limited evidence about the efficacy of cognitive interventions for Alzheimer’s disease (AD). However, aside from the methodological quality of the studies analyzed, the methodology used in previous meta-analyses is itself a risk of bias as different types of effect sizes (ESs) were calculated and combined. This study aimed at examining the results of nonpharmacological interventions for AD with an adequate control of statistical methods and to demonstrate a different approach to meta-analysis. Method: ESs were calculated with the independent groups pre/post design. Average ESs for separate outcomes were calculated and moderator analyses were performed so as to offer an overview of the effects of bias. Results: Eighty-seven outcomes from 19 studies (n = 812) were meta-analyzed. ESs were small on average for cognitive and functional outcomes after intervention. Moderator analyses showed no effect of control of bias, although ESs were different from zero only in some circumstances (e.g., memory outcomes in randomized studies). Cognitive interventions showed no more efficacy than placebo interventions, and functional ESs were consistently low across conditions. Conclusions: cognitive interventions delivered may not be effective in AD probably due to the fact that the assumptions behind the cognitive interventions might be inadequate. Future directions include a change in the type of intervention as well as the use of outcomes other than standardized tests. Additional studies with larger sample sizes and different designs are needed to increase the power of both primary studies and meta-analyses.

Efficacy of Cognitive Rehabilitation in Alzheimer Disease: A 1-Year Follow-Up Study

“…11 Cognitive training and cognitive stimulation may have modest effects on cognition but failed to demonstrate significant functional benefit and to show generalization to other domains than the ones trained. 7,[12][13][14] This could, partially at least, be explained by the neurodegenerative process per se. In fact, both cognitive training and cognitive stimulation require some learning, recalling, and controlled cognitive strategies, that is, processes that are impaired by the brain pathology.…”

The Effects of Cognitive Training Program for Cognitively Impaired Older Adults: A Pilot Randomized Control Trial

“…5 Other results were consistent with findings from meta-analyses that suggest cognitive training does not benefit persons with cognitive impairment. 4,9 For example, negligible effect sizes were found on measures of five cognitive domains and the measures of language and visual-spatial skills showed declines. Finally, measures of depressive symptoms, frequency of behavioral problems, daily functioning, and quality of life showed no improvements.…”

“…These results are consistent with previous research suggesting that even when cognitive functioning improves, benefits do not necessarily generalize to everyday functioning. 9 Follow-up interviews revealed that the program was well received among staff. Staff reportedly found the classes easy to administer and incorporate into their normal activity schedule, and classes required minimal (<10 min) preparation and clean up time.…”

“…4 Another meta-analysis of 19 studies concluded effect sizes were negligible to low on cognitive and functional outcome measures and the majority of studies were of low to moderate scientific quality. 9 In addition, even when benefits occurred, there was no evidence that benefits transferred to untrained tasks or everyday situations.…”

Environmental and Cognitive Enrichment in Childhood as Protective Factors in the Adult and Aging Brain

“…Taken together, these arguments constitute a worldwide health issue. Given the absence of striking effective pharmacological (Bahar-Fuchs et al, 2013;Cooper et al, 2013;Epelbaum et al, 2017) or cognitive (Sitzer et al, 2006;Olazarán et al, 2010;Woods et al, 2012;Bahar-Fuchs et al, 2013;Gates and Sachdev, 2014;Nelson and Tabet, 2015;Oltra-Cucarella et al, 2016) treatment once the pathology has begun, many studies examined modifiable risks and protective factors of dementia before the onset of clinical symptoms. One of the main factors considered, along with genetics, environment and lifestyle (e.g., diet, urban vs. rural lifestyle), seems to be CR.…”