Some types of dementia fit into more than one of these classifications. For example, Alzheimer's disease is considered both a progressive and a cortical dementia.
Alzheimer's disease (AD) is the most common cause of dementia in people aged 65 and older. Experts believe that up to 4 million people in the United States are currently living with the disease: one in ten elders over the age of 65 and nearly half of those over 85 have AD. At least 360,000 Americans are diagnosed with AD each year and about 50,000 are reported to die from it.
In most people, symptoms of Alzheimer's appear after age 60. Alzheimer's disease usually causes a gradual decline in cognitive abilities, usually during a span of 7 to 10 years. Nearly all brain functions, including memory, movement, language, judgment, behavior, and abstract thinking, are eventually affected.
AD is characterized by two abnormalities in the brain: amyloid plaques and neurofibrillary tangles. Amyloid plaques, which are found in the tissue between the nerve cells, are unusual clumps of a protein called beta amyloid along with degenerating bits of neurons and other cells.
Symptoms of Alzheimer's Disease
In the early stages of Alzheimer's disease, people may experience memory impairment, lapses of judgment, and subtle changes in personality. As the disorder progresses, memory and language problems worsen and people begin to have difficulty performing activities of daily living, such as balancing a checkbook or remembering to take medications. They also may have difficulty navigating an unfamiliar route, become disoriented about places and times, suffer delusions (such as the idea that someone is stealing from them or that their spouse is being unfaithful), or become short-tempered and hostile.
During the late stages of the disease, elders begin to lose the ability to control motor functions. They may have difficulty swallowing and lose bowel and bladder control. They eventually lose the ability to recognize family members and to speak. As Alzheimer's progresses, it begins to affect the person's emotions and behavior. Most people with AD eventually develop symptoms such as aggression, agitation, depression, sleeplessness, or delusions.
How Long Do People with Alzheimer's Live?
On average, people with Alzheimer's disease live for 8 to 10 years after they are diagnosed. However, some people live as long as 20 years. People with AD often die of aspiration pneumonia because they lose the ability to swallow late in the course of the disease.