Alzheimer’s disease

Alzheimer's disease (AD) is a slowly progressive form of dementia, which is a progressive, acquired impairment of intellectual functions. Memory impairment is a necessary feature for the diagnosis. Change in one of the following areas must also be present for any form of dementia to be diagnosed: language, decision-making ability, judgment, attention, and other related areas of cognitive function and personality. The rate of progression is different for each person. If AD develops rapidly, it is likely to continue to progress rapidly. If it has been slow to progress, it will likely continue on a slow course.

Alternative Names

Senile dementia/Alzheimer's type (SDAT)

Causes, incidence, and risk factors

The cause of Alzheimer's disease (AD) is not known, but it is not a part of normal aging. Prior theories regarding the accumulation of aluminum, lead, mercury, and other substances in the brain have been disproved. A diagnosis of AD is made based on characteristic symptoms and by excluding other causes of dementia. It can be confirmed by microscopic examination of a sample of brain tissue after death. Brain tissue shows "neurofibrillary tangles" (twisted fragments of protein within nerve cells that clog up the cell), "neuritic plaques" (abnormal clusters of dead and dying nerve cells, other brain cells, and protein), and "senile plaques" (areas where products of dying nerve cells have accumulated around protein). Although these changes occur to some extent in all brains with age, there are many more of them in the brains of people with AD. The destruction of nerve cells (neurons) leads to a decrease in neurotransmitters (substances secreted by a neuron to send a message to another neuron). The correct balance of neurotransmitters is critical to the brain. Three neurotransmitters commonly affected by AD are acetylcholine, serotonin, and norepinephrine -- with acetylcholine being the most affected. By causing both structural and chemical problems in the brain, AD appears to disconnect areas of the brain that normally work together. As many as 4 million Americans currently suffer from AD. The most important risk factors for dementia are old age and a family history of dementia. The older you get, the greater your risk of developing AD . About 10 percent of all people over 70 have significant memory problems and about half of those are due to AD. The number of people with AD doubles each decade past age 70. Having a close blood relative who developed AD increases risk. Because women usually live longer than men, they are more likely to develop AD. There are two types of AD -- early onset and late onset. In early onset AD, symptoms first appear before age 60. Some early onset disease runs in families and involves autosomal dominant , inherited mutations that may be the cause of the disease. So far, three early onset genes have been identified. Early onset AD is less common, resulting in about 5-10% of cases. Late onset AD, the most common form of the disease, develops in people 60 and older and is thought to be less likely to occur in families. Late onset AD may run in some families, but the role of genes is less direct and definitive. These genes may not cause the problem itself, but simply increase the likelihood of formation of plaques and tangles or other AD-related pathologies in the brain.

Signs and tests

The first step in diagnosing Alzheimer's disease is to establish that dementia is present. Second, the type of dementia should be clarified. A health care provider will take a history, do a physical exam (including a neurological exam), and do a mental status examination. Tests may be ordered to help determine if there is a treatable condition that could cause dementia or contribute to the worsening of AD. These conditions include thyroid disease, vitamin deficiency, brain tumor, drug and medication intoxication, chronic infection, and severe depression. AD usually has a characteristic pattern of symptoms and can be diagnosed by history and physical exam by an experienced clinician. Tests that are often done to evaluate or exclude other causes of dementia include computed tomography (CT), magnetic resonance imaging (MRI), and blood tests. In the early stages of dementia, brain image scans may be normal. In later stages, an MRI may show a decrease in the size of the cortex of the brain or of the area of the brain responsible for memory (the hippocampus). While the scans do not confirm the diagnosis of AD, they do exclude other causes of dementia (such as stroke and tumor).


AD cannot be cured and the impaired functions cannot be restored. Currently, the progression can be slowed but not stopped. Treatment focuses on attempting to slow the progression; managing the behavior problems, confusion, and agitation; modifying the home environment; and most importantly, supporting the family. As the disease progresses, it may take a greater toll on the family than the patient. DRUG TREATMENT There are currently three drugs available to try to slow the progression of the disease and possibly improve cognitive function. These three are tacrine (Cognex), donepezil (Aricept), and rivastigmine (Exelon). All three affect the level of acetylcholine (a neurotransmitter) in the brain. All three have potential side effects, such as nausea and vomiting. Tacrine, the first drug of this type approved, also causes an elevation in liver enzymes and must be taken four times a day. It is now seldom used. Of the two other drugs, Aricept has been available longer. It is taken once a day and has been reported to improve or stabilize cognitive functioning and is well tolerated. Exelon, a new drug, shows a similar effectiveness like Aricept and is taken twice a day. New drugs are scheduled for release in the near future. To improve cognitive function, it may be necessary to stop medications that worsen confusion or that are not essential to the care of the person. This may include medications (such as anticholinergics, analgesics, cimetidine, central nervous system depressants, antihistamines, sleeping pills, and other medications). BEHAVIORAL PROBLEMS Underlying disorders that contribute to confusion should be identified and treated. These include heart failure, decreased oxygen (hypoxia), thyroid disorders, anemia, nutritional disorders, infections, and psychiatric conditions (such as depression). The correction of these medical and psychiatric disorders often greatly improves the patient's mental function. Medications may be required to control aggressive, agitated or dangerous behaviors. These are usually given in very low doses, with adjustment as required. Behavior modification may be helpful for some people in controlling unacceptable or dangerous behaviors. This consists of rewarding appropriate or positive behaviors and ignoring inappropriate behaviors (within the bounds of safety). MODIFYING THE HOME ENVIRONMENT The person with AD will need support in the home as the disease worsens. Family members or other caregivers can help by understanding how the person with AD perceives his or her world. Provide structured activities that promote the remaining abilities and reduce the effects of the compromised abilities. Simplify the patient's surroundings, and give frequent reminders, notes, lists of routine tasks, or directions for daily activities. Give the person with AD a chance to talk about their challenges and to participate in their own care. OTHER PRACTICAL STEPS The sensory functions of the person with AD should be evaluated. If deficits are found, the patient should be assisted by hearing aids, glasses, and cataract surgery as appropriate. General nutrition and health maintenance is important, but special diets or nutritional supplements are usually unnecessary. Exercise is important and should be encouraged. Eventually, 24-hour monitoring and assistance may be required to provide a safe environment, control aggressive or agitated behavior, and meet physiologic needs. This may include in-home care, nursing homes, adult day care, or convalescent homes.

Expectations (prognosis)

The probable outcome is poor. The disorder is usually not acute, but progresses steadily. Total disability is common. Death normally occurs within 15 years, usually from an infection or a failure of other body systems.


  • Loss of ability to function or care for self
  • Complications caused by immobility
  • Bedsores
  • Broken bones
  • Muscle contractures (loss of ability to move joints because of loss of muscle function)
  • Loss of ability to interact
  • Increased incidence of infections anywhere in the body
  • Failure of body systems
  • Reduced life span
  • Abuse by an over-stressed caregiver
  • Side effects of medications
  • Calling your health care provider

    Call your health care provider if someone close to you experiences symptoms of senile dementia/Alzheimer's type. Call your health care provider if a person with this disorder experiences a sudden change in mental status. (A rapid change may indicate other illness.) Discuss the situation with your health care provider if you are caring for a person with this disorder and the condition deteriorates to the point where you can no longer care for the person in your home.


    Currently there is no proven way to prevent AD. A vaccine is being developed, and early testing is under way. Various studies are under way to clarify the role of some common medications in the prevention of AD. Among these are non-steroidal anti-inflammatory drugs (NSAIDs), antioxidants (such as Vitamin E), estrogen replacement therapy, and ginkgo biloba. None of these are currently recommended, all of these have side effects, and all can interact with other medications. Consult a health care provider before considering or taking them.

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