Alzheimer's Overview

The causes of Alzheimer's disease are unknown, but there are some apparent risk factors. First, there's age: The number of people with Alzheimer's increases dramatically after age 65. Genetic inheritance seems to play a role, particularly if an immediate blood relation had the disease. Women are more likely to have Alzheimer's because they live longer than men­­.

There are three genes -- known as amyloid precursor protein, presenilin 1 and presenilin 2 -- associated with early-onset Alzheimer's. For "normal-onset" Alzheimer's, there is the apolipoprotein gene (ApoE), which moves cholesterol through the bloodstream. A certain form of this gene, found in 15 percent of the population, boosts a person's chances of developing normal-onset Alzheimer's [source: NIH].

Genetic abnormalities certainly play a role in the development of the disease, but researchers have considered many other possible risk factors for Alzheimer's, including advanced age, high cholesterol, lack of folate, head injuries, lack of exercise and even exposure to toxic substances. However, many of these risk factors have produced conflicting evidence regarding their roles in the development of the disease. Age, gender, heredity and genetics are among the most commonly accepted risk factors.

The Alzheimer's Brain

A person's brain may start experiencing some of the changes associated with Alzheimer's up to two decades before an official diagnosis is made [source: Alzheimer's Association]. Chief among the changes in an Alzheimer's patient's brain is the development of clumps called amyloid plaques and neurofibrillary tangles, particularly in the brain's learning and memory centers. Plaques crowd the areas between neurons and are made up of clumps of a protein known as beta-amyloid. Tangles appear within neurons and even people without Alzheimer's disease can have them, though they're far more numerous in the brains of those with Alzheimer's.

There's a lot that remains unknown about plaques and tangles, but scientists do know that they play key roles in the development of Alzheimer's disease and the disruption of brain function. Both appear to inhibit the ability of neurons to communicate with each other. Tangles, which are knotted threads of tau proteins, likely contribute to cell death, a key effect of Alzheimer's. Normally, in the human brain, nutrients and cell parts are transported through straight, parallel channels. Tangles disrupt these transport avenues and prevent those vital nutrients and cell parts from getting where they need to go.

As Alzheimer's disease progresses, brain cells start to die and neurotransmitter levels decrease. (Neurotransmitters are the chemicals that transmit messages through the brain.) The brain also develops inflammation, though doctors don't know whether inflammation represents a positive or negative response to the plaques and tangles [source: Mayo Clinic]. Inflammation could be the result of the body's immune system attacking dying, tangle-filled cells.

While each patient is an individual case, mild to moderate Alzheimer's usually lasts two to 10 years, while advanced Alzheimer's can persist for up to five years [source: Alzheimer's Association]. The symptoms of Alzheimer's disease often aren't noticeable when they begin. Occasional lapses of memory are seen as common behavior for seniors and don't necessarily mean that someone is sick, though it is one of Alzheimer's early symptoms. Experts also point out that while forgetting unfamiliar people is not unusual, it isn't normal to forget those who one interacts with regularly.

As the disease progresses, severe forgetfulness sets in. A person will forget how to do things, even those that have been part of a daily routine for years. He or she will have difficulty remembering who people are. Thinking becomes muddled. The patient may have trouble assessing and judging situations or following directions. So-called "abstract thinking," such as manipulating information or numbers in one's head, is a particular problem. There can also be problems with spatial sense -- determining the locations of people and things relative to one's self.

At first a patient may have trouble remembering a word or phrase, but eventually, basic communication skills become impaired. Reading, writing and speaking all prove difficult. In moderate to advanced stages of Alzheimer's disease, a person can become confused, have mood swings, appear restless and wander off. Even a patient's personality may change, characterized by depression, restless or aggressive behavior, and anxiety.

Near end stage, an Alzheimer's patient must receive constant monitoring and care. By this point, neurons have died throughout the brain. The brain has shrunk, particularly in the cortex and hippocampus.

With Alzheimer's, there are many related diseases and complications, some of which can be fatal. Falls or accidents caused by loss of balance, disorientation or wandering off are common. These incidents may cause death on their own or may lead to other potentially deadly complications -- surgery, infections such as pneumonia, blood clots. In fact, while Alzheimer's disease is 100 percent fatal, the most common cause of death for those with the disease is some other acquired infection [source: NINDS]. But some states still list Alzheimer's disease as the cause of death in these cases, however. It's important to note that a patient can die from Alzheimer's itself: For example, the brain can become so damaged that a sufferer may no longer "know" how to breathe or may choke on food.

On the next page, we'll take a look at how a doctor diagnoses Alzheimer's disease.

The main problem with diagnosing Alzheimer's disease is that it can only be done with certainty by examining brain tissue after the patient has died. A doctor can look for plaques, tangles and overall shrinkage in the brain of the deceased. With the living, doctors do the best they can, often making patients undergo a series of tests. These tests can yield a 90 percent success rate in correctly diagnosing the disease [source: Mayo Clinic]. The doctor might test various bodily fluids, such as blood, urine or spinal fluid. (A blood test can be used to see if the patient is genetically predisposed to develop Alzheimer's, though it can't produce an actual diagnosis.)

­­A brain scan -- MRI, PET or CT scan -- is another useful tool, allowing the doctor to look for unusual formations in the brain. The doctor will also conduct an interview in which he or she asks the patient about memory, any health problems (past and present), difficulties performing routine tasks, any trouble remembering faces and names, and other possible symptoms. He or she will also conduct exercises that test attention span, counting abilities and short-term versus long-term memory. If the patient has a caregiver or close family members, the doctor may also interview them. Above all, it's important that a doctor eliminates other potential causes of the patient's problems; other forms of dementia, minor strokes and mild cognitive impairment could all produce some of the symptoms of Alzheimer's disease.

­In recent research into Alzheimer's diagnosis, use of brain scanning and brain imaging is particularly popular. The results of a study released in August 2008 show that PET scans may yield important insights into detecting plaques, believed to be one of the main culprits in the disruption of brain function in Alzheimer's patients [source: NIH/Reuters]. Early diagnosis allows doctors to decide whether a patient may benefit from one of the drugs proven to temporarily stave off the disease's symptoms.

Some people choose to have genetic testing in order to determine whether they have the genes associated with early-onset Alzheimer's or if they have the Alzheimer's-associated form of the ApoE gene. However, some people carry ApoE and never develop Alzheimer's disease. Still, genetic testing can help a person learn more about his or her susceptibility to Alzheimer's, particularly the early-onset variety, and offers an opportunity to discuss with a doctor how to monitor possible symptoms.

On the next page, we'll take a look at how doctors treat Alzheimer's disease.

Alzheimer's disease has no cure, but there are drugs that can help if administered in the disease's early stages. Some recently developed treatments have tried to use several drugs in combination. Drugs may also be used to treat ancillary symptoms like insomnia, depression and anxiety, or to guard against infection.

Cholinesterase inhibitors are one class of Alzheimer's drug. Donepezil, rivastigmine and galantamine all work to boost neurotransmitter levels, though some of these drugs can produce unpleasant side effects. Most Alzheimer's drugs are used in the disease's early stages, though donepezil can be used to treat Alzheimer's disease in any of its stages. For people with mild cognitive impairment (MCI), donepezil can delay the development of Alzheimer's by up to a year [source: Mayo Clinic]. MCI is a transitional disease, characterized by cognitive problems more severe than those that accompany old age but less severe than the symptoms of Alzheimer's disease. As many as one in five Americans over 70 may have MCI. Some of them develop Alzheimer's disease; others only have MCI or eventually regain normal cognitive function [source: Mayo Clinic].

Memantime (brand name: Namenda) is used to treat advanced Alzheimer's disease. Initially used in Germany in the 1980s, it's the only drug approved exclusively for use in the disease's later stages. Memantime can be used alone or with a cholinesterase inhibitor. The drug is designed to guard neurons from glutamate, which, in Alzheimer's patients, can overly excite brain cells, causing their cell membranes to become more permeable, eventually leading to decreased function or cell death.

Memantine and all other approved Alzheimer's drugs are designed to slow down the disease or to improve quality of life. None can cure the disease, although the understanding of Alzheimer's has progressed dramatically in recent years. Now, a person may live up to 20 years with the disease. Scientists are now looking at using drugs in combination with one another and at new drugs that directly attack the neurofibrillary tangles that develop in neurons, potentially leading to more effective treatments.

Despite the advances made in the field of Alzheimer's research, life can be extraordinarily difficult for those with advanced Alzheimer's and for the families of the afflicted. To watch a friend or family member gradually degenerate can be excruciating. Numerous organizations, books, support groups, doctors and other resources can help those who have the disease or people who must take care of a sick loved one.

For more information about Alzheimer's disease and related topics, please check out the links on the next page.