Comparative efficacy of various exercise interventions on cognitive function in patients with mild cognitive impairment or dementia: A systematic review and network meta-analysis

Background: Exercise is a promising nonpharmacological therapy for cognitive dysfunction, but it is unclear which type of exercise is most effective. The objective of this study was to compare and rank the effectiveness of various exercise interventions on cognitive function in patients with mild cognitive impairment (MCI) or dementia and to examine the effects of exercise on the symptoms relevant to cognitive impairment. Methods: We searched PubMed, Web of Science, Embase, Cochrane Central Register of Controlled Trials, SPORTDiscus, and PsycInfo through September 2019 and included randomized controlled trials that examined the effectiveness of exercise interventions in patients with MCI or dementia. Primary outcomes included global cognition, executive cognition, and memory cognition. Secondary outcomes included activities of daily living, neuropsychiatric symptoms, and quality of life. Pairwise analyses and network meta-analyses were performed using a random effects model. Results: A total of 73 articles from 71 trials with 5606 participants were included. All types of exercise were effective in increasing or maintaining global cognition, and resistance exercise had the highest probability of being the most effective intervention in slowing the decrease in global cognition (standard mean difference (SMD) = 1.05, 95% confidence interval (95%CI): 0.56-1.54), executive function (SMD = 0.85, 95%CI: 0.21-1.49), and memory function (SMD = 0.32, 95%CI: 0.01-0.63) in patients with cognitive dysfunction. Subgroup analyses for patients with MCI revealed different effects, and multicomponent exercise was most likely to be the optimal exercise therapy for preventing the decline of global cognition (SMD = 0.99, 95%CI: 0.44-1.54) and executive function (SMD = 0.72, 95%CI: 0.06-1.38). However, only resistance exercise showed significant effects on memory function for patients with MCI (SMD = 0.35, 95%CI: 0.01-0.69). Exercise interventions also showed various effects on the secondary outcomes. Conclusion: Resistance exercise has the highest probability of being the optimal exercise type for slowing cognitive decline in patients with cognitive dysfunction, especially in patients with dementia. Multicomponent exercise tends to be most effective in protecting global cognition and executive function in patients with MCI.