Exercise Interventions for Older Adults with Alzheimer's Disease: A Systematic Review and Meta-Analysis.

OBJECTIVE: Increased Alzheimer's disease (AD) prevalence paired with improved ability to diagnose the disease at earlier stages now, more than ever, necessitates interventions that will support the AD population for extended periods of time. Even with the substantial body of literature available, the effectiveness of physical exercise (PE) on various cognitive domains and the optimal dosage of PE are yet to be confirmed. Therefore, our objectives were to determine 1) the effectiveness of PE on cognitive function in older adults with AD, and 2) the optimal PE dosage for targeted outcomes. DATA SOURCES: The search was carried out across Embase, PsycInfo, and Ovid Medline databases. STUDY SELECTION: Of an initial return of 1,001 articles, 142 remained after title and abstract review, and 21 after full text review. DATA EXTRACTION: Primary outcomes extracted from included articles spanned four cognitive domain outcomes (global cognition, memory, language, attention, and executive function). Data on secondary outcomes included activities of daily living, emotional well-being, quality of life, and caregiver burden. DATA SYNTHESIS: The 21 included studies were published between 1991 and 2020 and sample sizes ranged from 12 to 494. Results confirm significant improvement in 4 of 5 cognitive domains favoring PE versus control conditions. Similarly, results favored exercise over control conditions for activities of daily living, emotional well-being, and quality of life outcomes, but not caregiver burden. The optimal PE dose was determined to be less than 60 minutes at least 3 times per week as compared to fewer more intense bouts. CONCLUSIONS: The results of this systematic review and meta-analysis provide important insight into the effectiveness of exercise on cognitive outcomes and guidance on the most effective PE parameters for optimizing cognitive function in AD.