Alzheimer's disease is the most common cause of dementia, accounting for 60 to 80 percent of dementia cases. The majority of people with Alzheimer's are aged 65 and older. Up to 5 percent of people with this disease have early onset Alzheimer's (also known as younger-onset), which often appears when someone is in their 40s or 50s.
Alzheimer's worsens over time. Dementia symptoms gradually worsen over years. The most common early symptom of Alzheimer's is difficulty remembering newly learned information, because Alzheimer's changes typically begin in the part of the brain that affects learning. As Alzheimer's advances through the brain and leads to increasingly severe symptoms, including disorientation, mood, and behavior changes; deepening confusion about events, time, and place; unfounded suspicions about family, friends, and professional caregivers; more serious memory loss and behavior changes; and difficulty speaking. Eventually even walking and swallowing problems can develop.
People with memory loss or Alzheimer’s may find it hard to recognize that they have a problem. Signs of dementia may be more obvious to family members or friends. Patients 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.
Alzheimer's and the Brain:
Microscopic changes in the brain begin long before the first signs of memory loss.
The brain has 100 billion nerve cells (neurons). Each nerve cell connects with many others to form communication networks. Groups of nerve cells have special jobs. Some are involved in thinking, learning, and remembering. Others help us see, hear, and smell.
To do their work, brain cells operate like tiny factories. They receive supplies, generate energy, construct equipment, and get rid of waste. Cells also process and store information, and communicate with other cells. Keeping everything running requires coordination, as well as large amounts of fuel and oxygen.
Scientists believe Alzheimer's disease prevents parts of a cell's factory from running well. They are not sure where the trouble starts. But just like a real factory, backups and breakdowns in one system cause problems in other areas. As damage spreads, cells lose their ability to do their jobs and eventually die, causing irreversible changes in the brain.
The characteristic pathology of Alzheimer’s disease, “plaques and tangles” are the prime suspects in damaging nerve cells, and tend to spread through the cortex as the disease progresses.
Plaques are deposits of a protein fragment called beta-amyloid (BAY-tuh AM-uh-loyd) that builds up in the spaces between nerve cells.
Tangles are twisted fibers of another protein called tau (rhymes with “wow”) that builds up inside cells.
Although most people develop some plaques and tangles as they age, those with Alzheimer's tend to develop far more. They also tend to develop them in a predictable pattern, beginning in areas important for memory before spreading to other regions.
Scientists do not know exactly what role plaques and tangles play in Alzheimer's disease. Most experts believe they somehow play a critical role in blocking communication among nerve cells and disrupting processes that cells need to survive. It is the destruction and death of nerve cells that causes memory failure, personality changes, problems carrying out daily activities, and other symptoms of Alzheimer's disease.
Alzheimer's has no current cure at the moment, but treatments for symptoms are available and research continues. Although current treatments cannot stop Alzheimer's from progressing, they can temporarily slow the worsening of dementia symptoms and improve quality of life for those with Alzheimer's and their caregivers. Today, there is a worldwide effort under way to find better ways to treat the disease, delay its onset, and prevent it from developing.
For more details, please refer to the Alzheimer’s Association:
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