Alzheimer’s disease is a progressive neurodegenerative disorder and the most common cause of dementia.
It most often emerges during a person’s mid-60s or older, although early-onset varieties exist. Its exact cause remains unclear.
Alzheimer’s and other dementias
Dementia describes a group of largely cognitive symptoms, such as memory loss, confusion, and declining reasoning skills, that interfere with a person’s daily life.
Although all dementias involve a loss of communication between brain cells due to damage, Alzheimer’s is unique in the presence of certain bundles of disorganized proteins called amyloid plaques and tau tangles. These clumps accumulate to toxic levels, killing the nerves in which they grow.
The root cause of Alzheimer’s remains unknown. Although genetics may be involved sometimes, environmental and lifestyle factors, such as air pollution and heavy alcohol consumption, also can raise the risk for developing the disorder. The greatest Alzheimer’s risk factor, however, remains age.
Course of Alzheimer’s
The nerve death associated with the disorder begins in the hippocampus, an area of the brain related to learning and memory. A person in the early stages often has trouble recalling recent events, misplacing objects, and finding the right words. Otherwise, however, they remain largely able to perform everyday activities such as driving and working.
These symptoms grow more pronounced as Alzheimer’s progresses, often accompanying changes in an individual’s moods and behavior. People in this stage may feel moody and withdrawn, and experience delusions that leads them to grow suspicious of others. They sometimes may grow violent. People at this stage generally require more help with everyday tasks and often become lost in familiar surroundings.
The symptoms of dementia grow severe in later stages. Alongside increasing memory loss, individuals lose much of their ability to communicate and to control their movement. They become more reliant upon assistance with daily activities and personal care, often resulting in the need for round-the-clock service. People at this stage can benefit greatly from hospice care.
Nerve death caused by amyloid plaques and tau tangles is widespread in Alzheimer’s and physically changes the brain in several ways.
Although nerve death begins in the hippocampus, it later spreads to the cerebral cortex, which associates with higher cognitive processes such as language, reasoning, and social behavior.
As neurons are lost over the course of the illness, neural networks become sparsely connected. This leads to the atrophy, or wasting away, of brain matter. This can be seen as a significant loss of brain volume.
The brains of people with Alzheimer’s also grow unable to effectively clear away cellular waste and toxins, triggering chronic inflammation. Cells known as microglia usually help to engulf and destroy such debris, but they fail to do so in the case of Alzheimer’s, for reasons that remain unknown.
People live with Alzheimer’s for widely varying lengths of time. Although the average survival time is estimated between three and 11 years from diagnosis, some people live for 20 years or longer.
Despite the lack of a cure, several treatments are available to reduce symptoms or slow their progression.
In addition to medications approved specifically for Alzheimer’s, patients often benefit from treating other conditions that may occur at the same time, such as depression and hearing loss. Regular doctor visits, social and intellectually engaging activities, and adaptations to daily life that prolong independence all help maintain a better quality of life.
Pneumonia caused by inhaling food or drink into the lungs (aspiration), which often is a concern in later stages, dehydration, falls, infections, and malnutrition are all common causes of mortality in Alzheimer’s cases.
Last updated: June 25, 2021
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