Alzheimer's Disease Overview
Alzheimer's disease (AD) is the most common cause of dementia in industrialized nations. Dementia is a brain disorder that interferes with a person's ability to carry out everyday activities.
- The brain of a person with Alzheimer's disease (see Multimedia file 1) has abnormal areas containing clumps (senile plaques) and bundles (neurofibrillary tangles) of abnormal proteins. These clumps and tangles destroy connections between brain cells.
- This usually affects the parts of the brain that control cognitive (intellectual) functions such as thought, memory, and language.
- Levels of certain chemicals that carry messages around the brain (neurotransmitters) are low.
- The resulting losses in intellectual ability are called dementia when they are severe enough to interfere with everyday functioning.
Alzheimer's disease affects mainly people aged 60 years or older.
- The risk of developing Alzheimer's disease continues to increase with age. People aged 80 years, for example, have a significantly greater risk than people aged 65 years.
- Millions of people worldwide have Alzheimer's disease. Many others have mild, or minimal, cognitive impairment, which frequently precedes dementia.
- The number of people with Alzheimer's disease is expected to rise substantially in the next few decades because of the aging of the population.
- The disease affects all races and ethnic groups.
- It seems to affect more women than men.
Alzheimer's disease is a progressive disease, which means that it gets worse over time. It cannot be cured or reversed by any known treatment.
- The symptoms often are subtle at first.
- Over time, people with the disease lose their ability to think and reason clearly, judge situations, solve problems, concentrate, remember useful information, take care of themselves, and even speak.
- Changes in behavior and personality are common.
- People with mild Alzheimer's disease usually require close supervision and help with everyday tasks such as cooking, shopping, and paying bills.
- People with severe Alzheimer's disease can do little on their own and require complete full-time care.
Because of this, Alzheimer's disease is considered a major public health problem.
- The cost of caring for people with the disease is estimated at over $100 billion per year in the United States. The average yearly cost per affected person is $20,000 to $40,000, depending on the severity of the disease.
- That cost doesn't take into account the loss of quality of life for the affected person, nor the physical and emotional toll on family caregivers.
Alzheimer's Disease Causes
We do not know exactly what causes Alzheimer's disease. There is probably not one single cause, but a number of factors that come together in certain people to cause the disease.
- Most experts believe that Alzheimer's disease is not a normal part of aging.
- While age is a risk factor for the disease, age alone does not seem to cause it.
- Family history is another risk factor. The disease does seem to run in some families. However, few cases of Alzheimer's disease are familial. Familial Alzheimer's disease often occurs at a younger age, between ages 30 and 60 years. This is called early-onset familial Alzheimer's disease.
At least three different genes have been linked to Alzheimer's disease.
- The one we know the most about controls production of a protein called apolipoprotein E (apoE), which helps in distribution of cholesterol through the body.
- Everyone has one of the 3 forms of the apoE gene. While one form seems to protect from AD, another form seems to increase the risk of developing the disease.
- The other genes-apart from ApoE-are known to be mutated in some people with the disease. These actually cause the disease in a few rare cases.
- Probably there are other genes that contribute to Alzheimer's disease, but we haven't found them yet.
Much of the research in Alzheimer's disease has focused on why and how some people develop deposits of the abnormal protein in their brains. Once the process is understood, it may be possible to develop treatments that stop or prevent it.
Medically Reviewed by a Doctor on 8/1/2014
Nestor Galvez-Jimenez, MD
Francisco Talavera, PharmD, PhD
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