Basic Facts About Alzheimer's Disease
Alzheimer's Disease is a degenerative brain disorder in which neurons, the specialized cells of the brain that process information,
stop functioning properly. The disease is named after Dr. Alois Alzheimer, a German doctor who first described the disease
in 1906 after performing an autopsy on the brain of a woman who had experienced severe mental problems in the years before her death.
Examination of her brain revealed the "neuritic plaques" and "neurofibrillary tangles" that are now hallmarks of the disease.
The incidence of Alzheimer's disease rises sharply with age. While only 2 to 5% of persons aged 65 show signs of Alzheimer's, 25 to 50% of persons aged 85 show symptoms of the disease. The average duration of the disease is about 7 to 10 years.
There are currently about 4.5 million U.S. citizens living with Alzheimer's disease. That number is expected to grow to over 14 million by the year 2050.
Approximately 30,000 to 50,000 people in the U.S. die from Alzheimer's disease each year.
The first signs of Alzheimer's disease are usually problems with memory. These problems often begin with relatively minor instances of forgetfulness, which can be a normal part of healthy aging. But in individuals with Alzheimer's disease they become increasingly frequent and severe, eventually interfering with normal activities of daily living.
Trouble signs include consistently forgetting to lock doors, turn off appliances, or take one's medication; repeatedly asking the same question or telling the same story; difficulty finding common words; and getting lost in familiar environments. Other early warning signs include poor judgment (e.g., leaving a child unattended) and changes in personal care (not bathing) or personality (mood swings or inappropriate bouts of anger, fear, or paranoia).
Next to show up are persistent impairments in attention and short-term/working memory. Attention problems often show up as an inability to concentrate or multi-task (do two or more things at once). Working-memory problems show up as an inability to hold information in mind for brief periods of time in order to accomplish an intended task. Problems with attention and working-memory lead to impairments in learning new information, as these two processes are critical in getting information into and out of long-term memory.
As the disease progresses, memory and attention problems get worse such that the person begins to forget significant life events, fails to recognize familiar people or objects, and has trouble performing well-learned tasks. Visual-spatial deficits may also occur. Eventually, the person becomes disoriented, unable to remember the day, the year, or even where they are. Communication becomes difficult and the person may become 'disinhibited', behaving inappropriately or having emotional, sometimes violent, outbursts. In the final stages of the disease, the person loses the ability to control their body, becoming incontinent and unable to feed or move themselves.
A diagnosis of Alzheimer's Disease is primarily made by clinical observation along with tests of memory and cognitive function. These are usually coupled with physical (blood and urine) tests designed to rule out alternative diagnoses. Along this line it is important to note that Alzheimer's Disease, although the most common, is only one of a spectrum of age-related conditions that can cause dementia. These other conditions include Vascular (multi-infarct) Dementia, Frontotemporal Dementia (Pick's Disease), and Lewy Body Dementia. Recently, neuroimaging techniques--including MRI scans which reveal brain stucture, and PET & SPECT scans which reveal brain activity and chemistry--are being used in the diagnosis of Alzheimer's and related dementias.
The primary neurological signs of Alzheimer's Disease are, first, the accumulation of a protein known as beta amyloid within the brain but outside of the nerve cells; clumps of beta-amyloid are called senile or neuritic plaques, and these plaques are thought to interfere with the communication between neurons. The second sign is the accumulation of abnormal filaments inside of neurons called neurofibrillary tangles which are believed to interfere with the normal operation of the cell; the protein making up these filaments is known as tau. There are also changes in the brains' neurochemistry, including abnormal changes in the levels of the brain's key neurotransmitters, as well as increased inflammation. Together, these changes lead to widespread atrophy of neurons, loss of dendritic and axonal connections, and neuronal death. At a more macroscopic level, the brain shows widespread loss of tissue, primarily in the temporal, parietal, and frontal lobes, along with enlargement of the ventricles.
The exact cause of Alzheimer's disease is unknown. Many scientists believe that multiple factors may be involved. Age is the most common risk factor, as the incidence of Alzheimer's rises significantly after age 65. Family history is also a risk factor, which suggests that genetic factors are involved. Presence of a specific form of the gene known as apolipoprotein E (ApoE) is associated with increased risk for Alzheimer's disease. Other risk factors include high blood pressure and high levels of cholesterol.
There is no known cure for Alzheimer's Disease although medications, cognitive stimulation, social support, and lifestyle changes have been shown to help with some symptoms.
Education, aerobic exercise, a healthy diet, and living an active, cognitively-challenging lifestyle are all associated with a reduced risk of Alzheimer's Disease.
To view a related fact sheet on Aging, Memory, & Cognition, click here.
To view a related fact sheet on Brain Fitness & Cognitive Training, click here.
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