|Alzheimer's is a common form of dementia, a general term for memory loss and other intellectual abilities serious enough to interfere with daily life. Alzheimer's disease accounts for 60 to 80 percent of dementia cases. Alzheimer's is a progressive disease, where dementia symptoms gradually worsen over a number of years. In early stages, memory loss is mild, but with late-stage Alzheimer's, individuals lose the ability to carry on a conversation and respond to their environment. Those with Alzheimer's live an average of eight years after their symptoms become noticeable to others, but survival can range from four to 20 years, depending on age and other health conditions. People with Alzheimers often have problems with sleeping or may experience changes in their sleep schedule. Scientists do not completely understand why these sleep disturbances occur. Along with changes in memory and behavior, sleep changes somehow result from the impact of Alzheimers on the brain. Many people with Alzheimers experience changes in their sleep patterns. As with changes in memory and behavior, sleep changes somehow result from the impact of Alzheimers on the brain. Many people with Alzheimers wake up more often and stay awake longer during the night. Brain wave studies show decreases in both dreaming and non-dreaming sleep stages. Those people who cannot sleep may wander, be unable to lie still, or yell or call out, disrupting the sleep of their caregivers.