Physical exercise is associated with a decreased rate of dementia,[156] and is effective in reducing symptom severity in those with AD.[157] Memory and cognitive functions can be improved with aerobic exercises including brisk walking three times weekly for forty minutes.[158] It may also induce neuroplasticity of the brain.[159] Participating in mental exercises, such as reading, crossword puzzles, and chess have shown a potential to be preventative.[153] Meeting the WHO recommendations for physical activity is associated with a lower risk of AD.[160]