Researchers have identified average levels of biological and anatomical brain changes associated with Alzheimer's disease over thirty years before symptoms appear. In those with genetic risk factors for Alzheimer's, researchers found changes in cognitive performance up to 15 years before becoming symptomatic. Changes in Tau levels in the cerebral spinal fluid appeared up to 34 years before dementia symptoms occurred, and physical changes to the medial temporal lobe were apparent up to 9 years before cognitive impairment was apparent.
