The Neuroprotective Role of Exercise in Alzheimer's Disease: An Integrative Review of Animal and Human Studies

Alzheimer's disease (AD), the leading cause of dementia, is characterized by progressive cognitive decline along with hallmark brain pathologies including amyloid-beta accumulation, hyperphosphorylated tau, neuroinflammation and neuronal mitochondrial dysfunction. As current pharmaceutical treatments only provide modest symptomatic improvement, there is an urgent need for effective non-pharmaceutical treatment options for the prevention or slowing down of this disease. This review synthesizes results from randomized controlled trials, observational studies, and animal model research on the ability of exercise to influence cognitive functions, brain structural changes, inflammatory processes, and neuroplasticity-related pathways. Exercise has demonstrated the capacity to enhance neurotrophic signaling, improve the regulation of mitochondria, improve cerebrovascular function and reduce pro-inflammatory cytokine levels in preclinical and mild cognitive impairment (MCI) subjects. Additionally, aerobic and resistance training has been shown to enhance physical performance and functional capacity. Furthermore, mind-body, dual-task and multimodal types of interventions may also provide additional cognitive and psychological benefits. Although the overall cognitive effect of exercise in individuals with established AD is generally small, it has been demonstrated that exercise can contribute to maintaining brain health through multiple interconnected metabolic, vascular and molecular pathways, thereby preserving cognitive reserve and slowing disease progression, particularly when initiated during early to midlife prior to the onset of AD symptoms. Therefore, future research will require establishing stage-specific exercise recommendations based on modality type, intensity and duration to achieve optimal clinical outcomes.