A comprehensive review synthesizing data from 58 longitudinal studies covering 2.4 million participants has confirmed that physical activity is the most powerful modifiable risk factor for dementia across all study populations and methodological approaches. The protective effect was present for aerobic exercise, resistance training, and combined programs, with a minimum effective dose of 150 minutes per week of moderate intensity activity.
Neuroimaging studies are beginning to reveal the structural brain changes through which exercise exerts its protective effect. Regular aerobic exercise is associated with measurably larger hippocampal volume, greater white matter integrity, and more efficient default mode network connectivity in older adults, changes that correspond to the preserved cognitive function and memory that exercise-active individuals demonstrate relative to sedentary peers.
