ALZHEIMER'S DISEASE

What is Alzheimer's disease?

Alzheimer's disease is a progressive and fatal brain disorder that gradually destroys a person's memory and ability to learn, reason, communicate, and make judgments.

Who gets Alzheimer's disease?

• Approximately 5.3 million Americans and more than 30 million people worldwide have Alzheimer's disease.
  
• The disease affects all races and ethnic groups.
  
• Alzheimer's disease seems to affect more women than men.
  
• Alzheimer's disease mainly affects people aged 60 years and older. The risk of developing Alzheimer's disease increases with age.

What causes Alzheimer's disease?

What exactly causes Alzheimer's disease is not known in most cases. Most often, a number of factors, rather than a single cause, come together in certain people to cause the disease.
Two forms of Alzheimer's disease have been recognized.

• In familial Alzheimer's disease, a person's genes directly cause the disease. This form of disease is very rare; only a few hundred families worldwide include individuals with the genes that cause this form of Alzheimer's disease. However, individuals who inherit these genes will almost certainly develop the disease, usually when younger than 65 years and sometimes as young as 30 years. At least three different genes have been found to be related early-onset or familial Alzheimer's disease.
  
• In sporadic Alzheimer's disease, the more common form of the disease, genes do not cause the disease; however, certain genetic mutations have been shown to increase an individual's risk of developing the condition. Cases of sporadic Alzheimer's disease occur in a less predictable manner than familial Alzheimer's disease, and usually not as many members in the same family acquire it compared to families with familial Alzheimer's disease
• What are symptoms of Alzheimer's disease?

While Alzheimer's disease progresses at different rates in different people, three general stages of Alzheimer's disease have been described.

• In the early stage (pre-clinical), symptoms of Alzheimer's disease are subtle. The main symptom is memory loss.
  
• In the middle, or intermediate, stage (mild cognitive impairment), individuals begin to lose their ability to think and reason clearly, judge situations, communicate, understand new information, and take care of themselves.
  
• As the disease progresses to the late stage (Alzheimer's' disease), individuals may experience changes in personality and behavior, anxiety, agitation, disorientation, paranoia, severe memory loss, loss of mobility, delusions, and hallucinations

• How can Alzheimer's disease be diagnosed?

  
  The neurodegenerative disorders in the brain that result in Alzheimer's disease start years, probably decades, before the beginning of clinical symptoms. This long period of time between the beginning of the pathological changes and the early symptoms opens a window of opportunity for early diagnosis and treatment. Unfortunately, at the present time no treatment is available to stop the progression of the disease.
  There are two main changes in brain tissue that are associated with Alzheimer's disease.
  
  1. The abundant presence of the so-called "senile plaques." These plaques are the result of the extracellular deposit of a protein fragment that is naturally produced inside the brain, known as amyloid A-beta 1-42. This protein accumulates in the parenchyma of the brain, that is, the area outside the nerve cells. The reason for this excessive accumulation is not clear but it is considered one of the landmarks of Alzheimer's disease.
     
  2. The presence (different from the plaques) of abnormal deposit of substances inside the cells of the brain. These intracellular deposits are called "neurofibrillary tangles" and "neuropil threads." The latter are composed of a protein called "Tau protein."
  Traditionally it was accepted that only a brain biopsy or an autopsy was able to confirm the diagnosis of Alzheimer's disease. This is still valid today; however the past 20 to 25 years have seen an increase in the study and evaluation of methods that can help to diagnose Alzheimer's disease in individuals before clinical symptoms are observed. The goal is to identify the persons that will develop Alzheimer's disease in the preclinical stages in order to be able to treat them before the disease develops to the clinical stage.
  There are functional and structural changes in the areas of the brain were the senile plaques and the neurofibrillary tangles deposit. These structural changes as well as the functional changes can be documented by specific imaging tests.
  Among these tests are those that measure structural changes in the brain like a CT scan and MRI; those that measure functional changes like brain glucose metabolism, as is the case with Positron Emission Tomography (FDG-PET), and more recently those tests that can specifically measure biochemical changes that are related to Alzheimer's disease as is the deposition of amyloid in the brain with special markers (PET PIB).
  Besides, new studies in biological fluids, specifically in the cerebrospinal fluid (CSF) have also added useful information that might help to predict who may develop Alzheimer's disease.
  Brain MRIs or CT scans might show brain changes such as diffuse or focal atrophy, while not diagnostic of Alzheimer disease, are considered a valid biomarker of Alzheimer disease neuropathology.
  Functional MRI (fMRI) evaluates the brain function by measuring the level of oxygenated hemoglobin in the brain. In Alzheimer's disease, fMRI shows areas in the brain with decreased activity that are associated with Alzheimer's disease
  PET requires the administration, usually intravenously, of a radioactive tracer. This test allows the measurement of metabolic function, brain metabolism, and binding to specific receptors in the brain. One of the most common tracers is fluorodeoxyglucose (FDG), which is glucose marked with a radioactive material [18 F]. FDG PET may detect changes in the brain in individuals prone to have Alzheimer's disease before they develop clinical symptoms of Alzheimer's disease.
  Another radioactive material that can be used as a tracer is known as Pittsburgh Compound B (PIB). This tracer has affinity with the amyloid protein. The PET PIB study might be of great utility to determine the extension of the deposits of beta amyloid in the brain.
  In addition ot their locations within the brain, the amyloid A beta 1-42 as well as the Tau proteins are also found in the liquid that bathes the surface of the brain, the cerebrospinal fluid (CSF). Samples of CSF can be easily obtained with a lumbar puncture or spinal tap. This is a relatively simple and safe procedure that consists of inserting a needle through the space between the lumbar vertebrae in the lower back. In general no anesthesia is needed, but sometimes a mild sedative is more than enough to perform the procedure. The analysis of the amyloid A beta 1-42 protein and the Tau protein in the CSF may yield important information regarding Alzheimer's disease.
  Studies of the CSF have shown that a pattern of low level of amyloid A beta 1-42 protein combined with high level of the Tau and phosphorylated Tau protein was detected in the majority (90%) of persons with clinical Alzheimer's disease; however, the same pattern was found in 39% of normal individuals. In persons with mild cognitive impairment (MCI) but no clear Alzheimer's disease the presence of the same pattern correctly identified the people that later on would develop Alzheimer's disease.
  However other clinical conditions might also produce similar results. For example deposits of amyloid A beta 1-42 can be seen in Parkinson's disease, in another form of dementia called Lewy Body disease, and also in cognitively normal individuals. Furthermore, a high concentration of Tau proteins may be seen after acute stroke or traumatic brain injuries.
  Some studies also suggest that these biomarkers may have prognostic value. The rate of deterioration may be faster in those with extremely abnormal results.
  In summary the radiological tests as well as measuring amyloid A beta 1-42 protein and Tau protein in the CSF, even while not diagnostic of Alzheimer's disease, may become an important addition to other clinical information in the diagnosis and prognosis of Alzheimer's disease.
  Who should get the tests?
  The answer is not clear and an individual should consult with their doctor about the convenience of having these tests performed. Some physicians recommend the test when the diagnosis of Alzheimer disease will have important consequences, for example, when making decisions about lifestyle, end of life treatments, etc.
  These tests can also help in the differential diagnosis with other forms of dementia that might have specific treatments available, such as normal pressure hydrocephalus or vascular dementia, or conditions that simulate dementia, as may be the case with severe clinical depression. However this should not be a common indication since in most instances these conditions can be diagnosed clinically or with other available methods.
  At the present time these diagnostic tests will not change the prognosis of the disorder since no treatment is available. However if a treatment becomes available these tests would become very important and useful

How can Alzheimer's disease be treated?

There is no cure for Alzheimer's disease. Treatment focuses on relieving and slowing down the progress of the symptoms, behavior changes, and complications.
Individuals with Alzheimer's disease should remain physically, mentally, and socially active for as long as they are able.

• Daily physical exercise, even a short walk, helps maximize body and mind functions and helps individuals maintain a healthy weight. A balanced diet that includes low-fat protein foods and lots of fruits and vegetables will help prevent malnutrition and maintain a healthy weight. Also, people with Alzheimer's disease should not smoke, both for health and safety reasons.
  
• Some studies suggest that mental activity might slow the progression of Alzheimer's disease, so engaging in as much mental activity as an individual can handle is important. Puzzles, games, reading, writing, and safe crafts are examples of mental activities. These activities should be of an appropriate level of difficulty that the individual is challenged but does not become frustrated.
  
• Social interaction is also important. Stimulating and enjoyable activities in which a person is engaged with others help to keep the mind active, which can decrease symptoms in most people with early or intermediate Alzheimer's disease. Most senior centers or community centers have scheduled activities that are suitable for those with Alzheimer's disease and other forms of dementia.

The symptoms of Alzheimer's disease can sometimes be relieved, at least temporarily, with medication. Many different types of medications have been or are being tried in dementia. The medications that have worked the best so far are cholinesterase inhibitors. Others include anti-inflammatory medications and vitamin E. 

• How can Alzheimer's disease be prevented?

  
  There is no known way to prevent Alzheimer's disease; however, being watchful for its symptoms and signs may allow earlier diagnosis and treatment. Appropriate treatment can slow or relieve symptoms and behavior problems in some people.
  Although some risk factors, such as age and genetics, can't be controlled, Alzheimer's disease may at least be delayed.
  Healthy lifestyle
  One way to reduce risk factors is to live a healthy lifestyle. Risk factors for Alzheimer's disease include heart disease, high blood pressure, and stroke. Brain health is linked to heart health, and if the heart has a hard time pumping blood, the brain won't get all the blood it needs. Research has found that people with high cholesterol and high blood pressure were six times as likely to develop Alzheimer's disease as those without elevated blood pressure and high cholesterol levels. With a healthy diet, the risk of developing heart disease, high cholesterol levels, and high blood pressure is reduced, and both the heart and brain are healthier.
  Keep active
  Keeping active - physically, mentally, and socially - may also help prevent Alzheimer's disease.
  
• Physical exercise is important. It prevents muscle weakness, maintains the overall fitness of the body and has also a positive effect on the cardiovascular system.
  
• Mental exercise - keeping the brain active -  might helps keep brain cells and the connections between them strong, further protecting against mental decline. Crossword puzzles, games, reading, writing, attending community classes, and watching educational programs can help a person stay mentally active.
  
• Research shows that people aged 75 years and older who regularly participate in social activities have a lower risk for developing certain types of dementia. The risk for those who participate in social activities that combine mental and physical activity is even lower. 
• Source: emedicinehealth.com
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