Impaired decision making is often an early signSign In medicine a sign is what a physician finds by examining a patient. For example, a patient with the symptom of pain might have signs of a fast heart rate, a pale face, a clammy touch and tenderness. of Alzheimer's diseaseAlzheimer's disease A neurological disease that affects memory and behaviour. It is characterized by beta-amyloid plaques and neurofibrillary tangles in the brain. There is no known cause but genetics and lifestyle are thought to play a role.. It gets worse as the disease progresses.