BDNF and dementia: The global number of dementia patients more than doubled from 1990 to 2016.1 Growing evidence has suggested that modifying risk factors might prevent or delay up to 40% of dementia incidence.2 Many studies have investigated the effects of physical activity (PA) on cognitive function3 and explored the potential mechanisms.4 PA increases cerebral blood flow, which increases brain-derived neurotrophic factor, enhances synaptic strength,5 and increases hippocampal capacity.6