Cognitive decline is a normal and universal part of aging. As people age, their activity level typically declines, not just physically, but mentally as well. Information from the senses is less reliable and processed less well. The systems in the brain get "sluggish." Even if people continue to be mentally active, it is usually in areas they have already mastered, and this will not improve other areas that experience decline.
Like a muscle, the brain deteriorates without appropriate exercise. When we don't give our brain the proper type and intensity of exercise, the result is less overall stimulation for the sensory, cognitive and motor systems.
