Alzheimer's disease (About Alzheimer's disease )

About Alzheimer's disease


Alzheimer's disease is a progressive, degenerative neurological disorder, meaning that the disorder gets worse over time. Alzheimer's disease is the most common cause of dementia among people over the age of 65 and it is thought that up to 4.5 million people have Alzheimer's disease, according to the National Institutes of Health (NIH). Five percent of people aged 65 to 74 and roughly 35 to 50 percent of people aged over 85 have the disorder, according to the National Institute of Neurological Disorders and Stroke (NINDS). However, despite the high prevalence of Alzheimer's disease among elderly people, Alzheimer's disease is not a normal part of aging.

Alzheimer's disease occurs when neurons in the brain die or break their connections with other neurons. This occurs because people with Alzheimer's disease experience atrophy of a part of the brain called the hippocampus. The hippocampus produces a neurotransmitter called acetylcholine. This chemical carries electrical signals from one neuron to another and is essential for memory, judgment and learning. In people with Alzheimer's disease, the cells that produce acetylcholine are damaged or killed and levels of the chemical gradually decline in the brain. This means that the electrical signals are not transmitted effectively from one neuron to another, causing the breakdown of neuron connections and the gradual atrophy of other parts of the brain.



The symptoms of Alzheimer's disease reflect where neuron connections are broken. For example, memory loss, a common early stage symptom, is caused by the disruption of neurons in the temporal and parietal lobes, which are associated with memory. Language problems, on the other hand, are thought to be caused by the disruption of the large networks of neurons that are associated with understanding and producing language.

People with Alzheimer's disease also have abnormal lesions called beta-amyloid plaques and neurofibrillary tangles. Beta-amyloid plaques are sticky pieces of protein and other matter than surround the neurons. Neurofibrillary tangles are twisted fibers also made from protein that build up inside the neurons. These plaques and tangles work together to disrupt brain function and are known to increase in quantity as the Alzheimer's disease progresses.

Certain factors of brain dysfunction in Alzheimer's disease are known, but much about the disease is unknown. The known factors include the onset and progress of dementia in patients and the presence of the plaques and tangles in their brains, which may be detected at autopsy. But specific causes remain unknown and the role of plaques and tangles, as either cause or result, are not well understood. It is thought that these amyloid plaques form very early in the disease stage and set of a cascade of inflammation and cell death throughout the affected portions of the brain. However, no one knows why the amyloid plaques form. Similarly, very little is understood about the tangles in the brain, or how they relate to the plaques.

The symptoms of Alzheimer's disease usually begin to appear around the age of 60. However, some people develop a condition called early-onset Alzheimer's disease as early as their 20s. Early-onset Alzheimer's disease is thought to be caused by a genetic disorder.

Alzheimer's disease can progress slowly or rapidly, depending on the individual. Patients generally live for an average of eight years after they are diagnosed with Alzheimer's disease, although they may live for up to 20 years. During the final stages of the disease, most patients require constant supervision and help performing basic self-care tasks such as bathing and feeding.

Most people do not die as a direct result of Alzheimer's disease. Instead, people with Alzheimer's disease are more likely to contract other medical conditions that can be fatal. Many people with Alzheimer's disease die from aspiration pneumonia (pneumonia caused by breathing in vomit or other fluids) because of the reduced ability to swallow in the later stages of the disease. In 2004, the most recent year for which figures are available, Alzheimer's disease was the fifth leading cause of death among people over 65 and the seventh leading cause of death overall, according to the Centers for Disease Control and Prevention (CDC).

Women are more commonly diagnosed with Alzheimer's disease than men, although this may be because women tend to live longer than men.

Although Alzheimer's disease is the leading cause of dementia, other conditions may cause dementia, including stroke, brain tumors and infections.