BDNF and dementia: Lower serum BDNF levels, older ages, lower physical activity, and hippocampal atrophy were associated with memory impairment independently. Impaired BDNF function (excluding proBDNF) combined with lower physical activity and hippocampal atrophy is associated with age-related memory impairment; therefore, BDNF is potentially used as a therapeutic target to prevent dementia.