Effects of physical activity on brain function and structure in older adults: A systematic review

•Physical activity effects are regionally specific to brain regions vulnerable to dementia.•Functional magnetic resonance imaging studies suggest a positive relationship between physical activity and cognitive performance.•Protective effects of physical activity appear to be greater in healthy older adults at genetic risk for dementia.•The high heterogeneity in PA assessment limits the establishment of PA recommendations.•Physical activity is a promising intervention in delaying cognitive decline and/or reducing risk of neurodegenerative disease. Despite increasing evidence that physical activity (PA) contributes to brain health in older individuals, both at the level of brain structure and function, this relationship is not yet well established. To explore this potential association, a systematic literature search was performed using PubMed, Scopus, and Web of Science, adhering to PRISMA guidelines. A total of 32 studies met the eligibility criteria: 24 cross-sectional and 8 longitudinal. Results from structural Magnetic Resonance Imaging (MRI) showed that PA associated with larger brain volumes (less brain atrophy) specifically in brain regions vulnerable to dementia, comprising the hippocampus, temporal, and frontal regions. Furthermore, functional MRI (fMRI) showed greater task-relevant activity in brain areas recruited in executive function and memory tasks. However, the dose-response relationship is unclear due to the high variability in PA measures. Further research using objective measures is needed to better understand which PA type, intensity, frequency, and duration, has the greatest protective effect on brain health. Findings highlight the importance of PA in both cognitive decline and dementia prevention.