Cognitive training in Alzheimer's disease: a meta-analysis of the literature

Objective: To systematically review the literature and summarize the effect of cognitive training (CT) for Alzheimer's disease (AD) patients on multiple functional domains. Method: Effect sizes (Cohen's d) were calculated for 17 controlled studies identified through a comprehensive literature review. Results: An overall effect size of 0.47 was observed for all CT strategies across all measured outcomes. Mean effect sizes were higher for restorative (0.54) than for compensatory (0.36) strategies. Domain-specific effect sizes ranged from 2.16 (verbal and visual learning) to -0.38 (visuospatial functioning). Data are also presented on the relative impact of restorative and compensatory strategies for each domain of functioning. Conclusion: CT evidenced promise in the treatment of AD, with primarily medium effect sizes for learning, memory, executive functioning, activities of daily living, general cognitive problems, depression, and self-rated general functioning. Restorative strategies demonstrated the greatest overall effect on functioning. Several limitations of the published literature are discussed.