Definition

     Alzheimer's disease is the most common cause of dementia, which is the loss of intellectual and social abilities severe enough to interfere with daily functioning. Dementia occurs in people with Alzheimer's disease because healthy brain tissue degenerates, causing a steady decline in memory and mental abilities.

Signs and symptoms

     Everyone has occasional lapses in memory. It's normal to forget the names of people whom you rarely see. But it's not a normal part of aging to forget the names of familiar people and objects.

     Alzheimer's disease — a progressive, degenerative brain disease — causes more than simple forgetfulness. It may start with slight memory loss and confusion, but it eventually leads to irreversible mental impairment that destroys a person's ability to remember, reason, learn and imagine.

     Most people with Alzheimer's share certain signs and symptoms of the disease. These may include:

• Increasing and persistent forgetfulness. At its onset, Alzheimer's disease is marked by periods of forgetfulness, especially of recent events or simple directions. But what begins as mild forgetfulness persists and worsens. People with Alzheimer's may repeat things and forget conversations or appointments. They routinely misplace things, often putting them in illogical locations. They frequently forget names, and eventually, they may forget the names of family members and everyday objects.

• Difficulties with abstract thinking. People with Alzheimer's may initially have trouble balancing their checkbook, a problem that progresses to trouble recognizing and dealing with numbers.

• Difficulty finding the right word. It may be a challenge for those with Alzheimer's to find the right words to express thoughts or even follow conversations. Eventually, reading and writing also are affected.

• Disorientation. People with Alzheimer's often lose their sense of time and dates, and may find themselves lost in familiar surroundings.

• Loss of judgment. Solving everyday problems, such as knowing what to do if food on the stove is burning, becomes increasingly difficult, eventually impossible. Alzheimer's is characterized by greater difficulty in doing things that require planning, decision making and judgment.

• Difficulty performing familiar tasks. Once-routine tasks that require sequential steps, such as cooking, become a struggle as the disease progresses. Eventually, people with advanced Alzheimer's may forget how to do even the most basic things.

• Personality changes. People with Alzheimer's may exhibit mood swings. They may express distrust in others, show increased stubbornness and withdraw socially. Early on, this may be a response to the frustration they feel as they notice uncontrollable changes in their memory. Depression often coexists with Alzheimer's disease. Restlessness also is a common sign. As the disease progresses, people with Alzheimer's may become anxious or aggressive and behave inappropriately.

Stages

• Mild — At the early stage of the disease, patients have a tendency to become less energetic or spontaneous, though changes in their behavior often go unnoticed even by the patients' immediate family.

• Moderate — As the disease progresses to the middle stage, the patient might still be able to perform tasks independently, but may need assistance with more complicated activities.

• Severe — As the disease progresses from the middle to late stage, the patient will undoubtedly not be able to perform even the simplest of tasks on their own and will need constant supervision. They may even lose the ability to walk or eat without assistance.

Causes

   Scientists do not yet fully understand what causes Alzheimer's disease. There probably is not one single cause, but several factors that affect each person differently. Age is the most important known risk factor for Alzheimer's disease. The number of people with the disease doubles every 5 years beyond age 65.

Risk factors

     Alzheimer's is a complex disease likely caused by a combination of factors — such as infection or reduced circulation — and genetic susceptibility. Although all the contributing factors may never be known, scientists have identified several common threads. They include:

• Age. Alzheimer's usually affects people older than 65, but can, rarely, affect those younger than 40. Less than 5 percent of people between 65 and 74 have Alzheimer's.   For people 85 and older, that number jumps to nearly 50 percent.

• Heredity. Your risk of developing Alzheimer's appears to be slightly higher if a first-degree relative — parent, sister or brother — has the disease. Although the genetic mechanisms of Alzheimer's among families remain largely unexplained, researchers have identified a few genetic mutations that greatly increase risk in some families. Three genetic mutations are known to cause early-onset Alzheimer's. In addition, one form of the apolipoprotein E (APOE) gene increases your chance of developing late-onset Alzheimer's.

• Sex. Women are more likely than men are to develop the disease, in part because they live longer.

• Lifestyle. The same factors that put you at risk of heart disease, such as high blood pressure and high cholesterol, may also increase the likelihood that you'll develop Alzheimer's disease. Poorly controlled diabetes is another risk factor. And keeping your body fit isn't your only concern — you've got to exercise your mind as well. Some studies have suggested that remaining mentally active throughout your life, especially in your later years, reduces the risk of Alzheimer's disease.

• Education levels. Studies have found an association between less education and the risk of Alzheimer's. Some researchers theorize that the more you use your brain, the more synapses you create, which provides a greater reserve as you age. It remains unclear, however, whether less education and less mental activity create a risk of Alzheimer's or if it's simply harder to detect Alzheimer's in people who exercise their minds frequently or who have more education.

• Toxicity. One long-standing theory is that overexposure to certain trace metals or chemicals may cause Alzheimer's. For a time, aluminum seemed a likely candidate, because some people with Alzheimer's have deposits of aluminum in their brains. After many years of studies, however, no one has been able to link aluminum exposure directly to Alzheimer's. At this point, there's no evidence that any particular substance increases a person's risk of Alzheimer's.

• Head injury. The observation that some ex-boxers eventually develop dementia suggests that serious traumatic injury to the head (for example, a concussion with a prolonged loss of consciousness) may be a risk factor for Alzheimer's. Several studies indicate a definite link between the two, but others show no link.

• Hormone replacement therapy. The exact role hormone replacement therapy may play in the development of dementia isn't yet clear. Throughout the 1980s and '90s, evidence seemed to show that estrogen supplements given after menopause could reduce the risk of dementia. But results from the large-scale Women's Health Initiative Memory Study indicated an increased risk of dementia for women taking estrogen after age 65. The verdict is not yet in on whether estrogen affects the risk of dementia if given at an earlier age.

Screening and diagnosis

     There's no one test to diagnose Alzheimer's disease. Typically, doctors start the diagnostic process by ruling out other diseases and conditions that also can cause memory loss.

     Small, undetected strokes, for example, can cause dementia by temporarily interrupting blood flow to the brain. People with Parkinson's disease, a degenerative nerve disorder, also can develop dementia. Depression, too, can cause lapses in memory. In addition, many older adults are on multiple medications that may impair their ability to think clearly.

     To help distinguish Alzheimer's disease from other causes of memory loss, doctors typically rely on the following:

• Medical history. Doctors may ask about a person's general health and past medical problems. They'll want to know about any problems a person may have in carrying out daily activities. If possible, doctors will also want to speak with a person's family or friends to get more information.

• Basic medical tests. Blood tests may be done to help doctors rule out other potential causes of the dementia, such as thyroid disorders or vitamin deficiencies.

• Mental status evaluation. These tests screen memory, problem-solving abilities, attention spans, counting skills and language. They help doctors pinpoint specific problems a person may have with cognition. For instance, doctors might test recent and long-term memory by asking: What day is it today? Or: When was World War II? Recall tests are another example. Doctors may list familiar objects, and then ask a person to repeat them immediately, and again five minutes later.

• Neuropsychological testing. Sometimes doctors undertake a more extensive assessment of memory, problem-solving abilities, attention spans, counting skills and language. This is especially helpful in trying to detect Alzheimer's and other dementias at an early stage. Doctors use formal psychological tests to determine if a person's mental abilities are as expected for his or her age and education. The patterns of any mental deficits observed during neuropsychological testing can help doctors sort out possible causes of dementia.

• Brain scans. Doctors may want to take a picture of the brain using a brain scan. Several types of brain scans are available — including a computerized tomography (CT) scan, a magnetic resonance imaging (MRI) scan and a positron emission tomography (PET) scan. By looking at images of the brain, doctors may be able to pinpoint any visible abnormalities. Researchers are studying whether brain scans can eventually be used to detect an increased risk of Alzheimer's in healthy people before symptoms begin.

     Using the methods above, doctors can accurately diagnose 90 percent of Alzheimer's cases. Alzheimer's can be diagnosed with complete accuracy only after death, using a microscopic examination of brain tissue, which checks for plaques and tangles.

     Genetic testing for Alzheimer's is in its beginning stages. Blood tests are available that can tell whether a person carries the genetic mutations believed to be associated with Alzheimer's, but the tests can't tell who will or will not get the disease.

Complications

     In advanced Alzheimer's disease, people may lose all ability to care for themselves. This can make them more prone to additional health problems such as:

• Pneumonia. Difficulty swallowing food and liquids may cause people with Alzheimer's to inhale (aspirate) some of what they eat and drink into their airways and lungs, which can lead to pneumonia.

• Infections. Urinary incontinence may require the placement of a urinary catheter, which increases the risk of urinary tract infections. Untreated urinary tract infections can lead to more serious, life-threatening infections.

• Falls and their complications. People with Alzheimer's may become disoriented, increasing their risk of falls. Falls can lead to fractures. In addition, falls are a common cause of serious head injuries, such as bleeding in the brain. Surgery to repair injury from a fall carries risks as well. For instance, prolonged immobilization — which may be necessary to recover from injuries related to a fall — increases the risk of a blood clot in the lungs (pulmonary embolism), which can be life-threatening.

Treatment

     Currently, there's no cure for Alzheimer's disease. Doctors sometimes prescribe drugs to improve symptoms that often accompany Alzheimer's, including sleeplessness, wandering, anxiety, agitation and depression. But only two varieties of medications have been proved to slow the cognitive decline associated with Alzheimer's.

• Cholinesterase inhibitors
  This group of medications — which includes donepezil (Aricept), rivastigmine (Exelon) and galantamine (Reminyl) — works by improving the levels of neurotransmitters in the brain. Donepezil has been approved by the Food and Drug Administration for the treatment of mild, moderate and severe Alzheimer's disease.

     Donepezil also appears to delay the onset of Alzheimer's for about a year in people who have mild cognitive impairment (MCI). People who have MCI have more memory problems than other people their age, but they are not demented.

     Cholinesterase inhibitors don't work for everyone. As many as half the people who take these drugs show no improvement. Other people may choose to stop taking the drugs because of the side effects, which include diarrhea, nausea and vomiting.

• Memantine (Namenda)
  The first drug approved to treat moderate to severe stages of Alzheimer's, memantine (Namenda), protects brain cells from damage caused by the chemical messenger glutamate. It sometimes is used in combination with a cholinesterase inhibitor. Memantine's most common side effect is dizziness, although it also appears to increase agitation and delusional behavior in some people.

Prevention

     Right now, there's no proven way to prevent the onset of Alzheimer's disease. Researchers had developed what looked to be a promising vaccine against Alzheimer's that worked by stopping deposits of beta-amyloid in the brain. Animal studies were so encouraging that human trials began in 2001. Unfortunately, they soon had to be stopped because some people experienced serious inflammation of the brain. While these results were disappointing, scientists learned from these experiments and many researchers continue to look for ways to reduce the risk of this disease. Several leads are hopeful, but still preliminary. They include:

• Healthy aging. Some of the most recent research indicates that taking steps to improve your cardiovascular health, such as losing weight, exercising and controlling high blood pressure and cholesterol, may also help prevent Alzheimer's disease.

• Nonsteroidal anti-inflammatory drugs (NSAIDs). Several studies have shown that the NSAIDs ibuprofen (Advil, Motrin, others), naproxen sodium (Aleve) and indomethacin (Indocin) may reduce the risk of developing Alzheimer's. This may be because inflammation appears to play a role in Alzheimer's. What isn't known, however, is whether inflammation is a cause of Alzheimer's or simply an effect of the disease. Because NSAIDs can cause serious gastrointestinal bleeding, clinical trials need to be completed before it's clear whether people should take NSAIDs solely to prevent Alzheimer's.

• Statins. These drugs — a class that includes atorvastatin (Lipitor), rosuvastatin (Crestor) and simvastatin (Zocor) — are normally used to lower cholesterol levels, but recent studies have shown that they may also reduce the risk of Alzheimer's disease. More studies are being done to determine exactly what role, if any, statins may have in Alzheimer's prevention.

• Selective estrogen receptor molecules (SERMs). A SERM called raloxifene (Evista) is used to protect against the bone loss associated with osteoporosis. It also appears to lower the risk of developing mild cognitive impairment, a memory disorder that often precedes Alzheimer's.

• Vitamin E and ginkgo. Both these substances have been linked to improvements in cognitive abilities, and their potential effects on Alzheimer's are being studied. One large study, however, showed that vitamin E has no effect on the development of Alzheimer's in people who have mild cognitive impairment.

• Mental fitness. Maintaining mental fitness may delay onset of dementia. Some researchers believe that lifelong mental exercise and learning may promote the growth of additional synapses, the connections between neurons, and delay the onset of dementia. Other researchers argue that advanced education gives a person more experience with the types of memory and thinking tests used to measure dementia. This advanced level of education simply may help some people "cover up" their condition until later.