Alzheimer’s disease is a progressive loss of mental function, characterized by degeneration of brain tissue, including loss of nerve cells and the development of senile plaques and neurofibrillary tangles.
- Forgetting recent events is an early sign, followed by increasing confusion, impairment of other mental functions, and problems using and understanding language and doing daily tasks.
- Symptoms progress so that people cannot function, causing them to become totally dependent on others.
- Doctors base the diagnosis on symptoms and results of a physical examination, mental status tests, blood tests, and imaging tests.
- Treatment involves strategies to prolong functioning as long as possible and may include drugs to slow the progression of the disease.
- How long people live cannot be predicted, but death occurs, on average, about 7 years after the diagnosis is made.
Most dementias are Alzheimer’s disease. In older people, it accounts for 50 to 70% of dementias. It is rare among people younger than 60. It becomes more common with increasing age. It affects less than 5% of people age 60 to 74, 19% of those age 75 to 84, but more than 30% of those older than 85.One in eight people aged 65 and over have the disease. It affects more women than men. In 2007 in the United States, over 5 million people had Alzheimer’s disease.
What cause Alzheimer’s disease is unknown, but genetic factors play a role. About 5 to 15% of cases run in families. Several specific gene abnormalities may be involved. Some of these abnormalities can be inherited when only one parent has the abnormal gene. That is, the abnormal gene is dominant. An affected parent has a 50% chance of passing on the abnormal gene to each child. In some of these cases, Alzheimer’s disease develops before age 60.
One gene abnormality affects apolipoprotein E (ago E) – the protein part of certain lipoproteins, which transport cholesterol through the bloodstream. There are three types of Apo E (e2, e3, and e4). People with the 34 type develop Alzheimer’s disease more commonly and at an earlier age than other people. In contrast, people with the e2 type seem to be protected against Alzheimer’s disease. People with the e3 type are neither protected nor more likely to develop the disease. (These associations have been studied primarily in whites and may not apply to other races). However, genetic testing for Apo E type cannot determine whether a specific person will develop Alzheimer’s disease. Therefore, this testing is not routinely recommended.
In Alzheimer’s disease, parts of the brain degenerate, destroying nerve cells and reducing the responsiveness of the remaining ones to many of the chemical messengers that transmit signals between nerve cells in the brain (neurotransmitters). The level of acetylcholine, a neurotransmitter that helps with memory, learning, and concentration, is low. Abnormalities in brain tissue consist of the following.
- Senile or neurotic plaques: Clumps of dead nerve cells containing an abnormal, insoluble protein called amyloid.
- Neurofibrillary tangles: Twisted stands of insoluble proteins in the nerve cell.
- Increased levels of tau: an abnormal protein that is a component of neurofibrillary tangles.
Such abnormalities develop to some degree in all people as they age but are much more numerous in people with Alzheimer’s disease.
Symptoms Of Alzheimer’s Disease
The symptoms of Alzheimer’s disease are similar to those of other dementias. They include memory loss, changes in personality, problems using language and doing daily tasks. Disorientation and disruptive behavior. Symptoms develop gradually, so for a while, many people continue to enjoy much of what they enjoyed before developing Alzheimer’s disease.
Symptoms usually begin subtly. People whose disease develops while they are still employed may not do as well in their jobs. In people who are retired and not very active, the changes may not be as noticeable.
The first sign may be forgetting recent events, although sometimes the disease begins with changes in personality. People may become emotionally unresponsive, depressed, or usually fearful or anxious.
Early in the disease, people become less able to use good judgment and think abstractly. Speech patterns may change slightly. People may use simpler words, a general word or many words rather than a specific word, or use words incorrectly. They may be unable to find the right word.
People with Alzheimer’s disease have difficulty interpreting visual and audio cues. Thus, they may become disoriented and confused. Such disorientation may make driving a car difficult. They may get lost on their way to the store. People may be able to function socially but may behave unusually. For example, they may forget the name of a recent visitor, and their emotions may change unpredictably and rapidly.
Many people with Alzheimer’s disease often have insomnia. They have trouble falling or staying asleep. Some people become confused about day and night.
At some point, psychosis (hallucinations, delusions, or paranoia) develops in about half of people with Alzheimer’s disease.
As Alzheimer’s disease progresses, people have trouble remembering events in the past. They may require help with eating, dressing, bathing and going to the toilet. Disruptive or inappropriate behavior, such as wandering, agitation, irritability, hostility, and physical aggression, is common. All sense of time and place is lost: People with Alzheimer’s disease may even get lost on their way to the bathroom at home. Their increasing confusion puts them at risk of falling.
Eventually, people with Alzheimer’s disease cannot walk or take care of their personal needs. They may be incontinent unable to swallow, eat, or speak. These changes put them at risk of undernutrition, pneumonia, and pressure sores (bedsores). Memory is completely lost. Ultimately, coma and death, often due to infections, result.
Progression is unpredictable. People live, on average, about 7 years after the diagnosis is made. Most people with Alzheimer’s disease who can no longer walk live no more than 6 months. However, how long people live varies widely.
Diagnosis Of Alzheimer’s Disease
If dementia is diagnosed in older people and their memory has gradually deteriorated, doctors consider Alzheimer’s disease the most likely cause. The diagnosis is based partly on the following.
- Symptoms, which are identified by asking the person and family members or other caregivers questions
- Results of physical examination.
- Results of mental status tests.
- Results of additional tests, such as blood tests, computed tomography (CT), or magnetic resonance imaging (MRI).
Information from the additional tests helps doctors exclude other types and causes of dementia.
The diagnosis of Alzheimer’s disease is confirmed only when a sample of brain tissue is removed (after death, during an autopsy) and examined under a microscope. Then, the characteristic loss of nerve cells, neurofibrillary tangles, and senile plagues containing amyloid can be seen throughout the brain, particularly in the area of the temporal lobe that is involved in forming new memories.
Analysis of spinal fluid and poitron emission tomography has been suggested as ways to diagnose Alzheimer’s disease during life. However, these tests are used so far only in research.
Treatment Of Alzheimer’s Disease
Treatment involves general measures to provide safety and support, as for all dementias. The cholinesterase inhibitors donepezil, galantamine, and rivastigmine increase the level of the neurotransmitter acetylcholine in the brain. This level may be low. The drugs may temporarily improve cognitive function, including memory, but they do not slow the progression of the disease. About half of the people who have Alzheimer’s disease benefit from these drugs. For these people, the drugs effectively turn the clock back 6 to 9 months. These drugs are most effective in people with mild to moderate disease. The most common side effects include nausea, vomiting, weight loss, and abdominal pain or cramps.
Memantine appears to slow the progression of Alzheimer’s disease. Memantine can be used with a cholinesterase inhibitor.
Researchers continue to study drugs that may prevent or slow the progression of Alzheimer’s disease – for example, substances that may reduce the amount of amyloid deposited. Estrogen therapy for women, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen), and ginkgo biloba are being studied. But none has consistently proved to be effective. Moreover, estrogen appears to do more harm than good.
Vitamin E is an antioxidant that may help protect nerve cells from damage or help them function better. Vitamin E may help preserve the ability to do basic daily tasks, such as dressing and bathing, but it does not improve thinking or memory problems in people with Alzheimer’s disease. When taken in reasonable amounts, vitamin e is safe and inexpensive and may slightly benefit some people. Before people take any dietary supplement, they should discuss the risks and benefits with their doctor.