what is alzheimer's disease?

Dementia is global impairment of brain functioning that seriously affects a person's ability to carry out daily activities. Alzheimer's disease (AD) is the most common form of dementia among older people. It involves the parts of the brain that control thought, memory, and language. Every day scientists learn more, but right now the causes of AD are still unknown, and there is no cure. The word dementia was derived from the Latin words 'de' meaning from, and 'mens' meaning mind.

Scientists estimate that AD affects roughly one in every ten persons over the age of 65 and older. The disease usually begins after age 60, and the risk goes up with age. While younger people also may get AD, it is much less common. About 3 percent of men and women ages 65 to 74 have AD, and nearly half of those age 85 and older may have the disease. It is important to note, that AD is not a normal part of aging.

AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. He found abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles). Today, these plaques and tangles in the brain are considered hallmarks of AD.

Scientists also have found other brain changes in people with AD. There is a loss of nerve cells in areas of the brain that are vital to memory and other mental abilities. There also are lower levels of chemicals in the brain that carry complex messages back and forth between nerve cells. AD may disrupt normal thinking and memory by blocking these messages between nerve cells.

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

Family history is another risk factor. Scientists believe that genetics may play a role in many AD cases. For example, familial AD, a rare form of AD that usually occurs between the ages of 30 and 60, can be inherited. However, in the more common form of AD, which occurs later in life, no obvious family pattern is seen. One risk factor for this type of AD is a protein called apolipoprotein E (apoE). Everyone has apoE, which helps carry cholesterol in the blood. The apoE gene has three forms. One seems to protect a person from AD, and another seems to make a person more likely to develop the disease. Other genes that increase the risk of AD or that protect against AD probably remain to be discovered.

Scientists still need to learn a lot more about what causes AD. In addition to genetics and apoE, they are studying education, diet, environment, and viruses to learn what role they might play in the development of this disease.

What Are the Symptoms of AD?
AD begins slowly. At first, the only symptom may be mild forgetfulness. People with AD may have trouble remembering recent events, activities, or the names of familiar people or things. Simple math problems may become hard to solve. Such difficulties may be a bother, but usually they are not serious enough to cause alarm.
However, as the disease goes on, symptoms are more easily noticed and become serious enough to cause people with AD or their family members to seek medical help.

For example, people in the later stages of AD may forget how to do simple tasks, like brushing their teeth or combing their hair. They can no longer think clearly. They begin to have problems speaking, understanding, reading, or writing. Later on, people with AD may become anxious or aggressive, or wander away from home. Eventually, patients need total care.

How is AD Diagnosed?
An early, accurate diagnosis of AD helps patients and their families plan for the future. It gives them time to discuss care options while the patient can still take part in making decisions. Early diagnosis also offers the best chance to treat the symptoms of the disease.

There is no specific diagnostic test for Alzheimer's disease. The illness is diagnosed on the basis of a typical history and the absence of abnormal findings on clinical examination, blood tests and brain scans. The characteristic history is a gradual onset and a slow progression of intellectual impairment.

Doctors use several tools to diagnose AD:

• Firstly, the presence of intellectual (cognitive) impairment has to be confirmed. This is usually done by a short screening test called the Mini-Mental Status Examination. The test counts out of 30 and a score of 24 or below indicates significant cognitive impairment.
• A complete medical history includes information about the person's general health, past medical problems, and any difficulties the person has carrying out daily activities.
• Medical tests - such as tests of blood, urine, or spinal fluid - help the doctor find other possible diseases causing the symptoms.
• Neuropsychological tests are more sensitive tests that measure memory, problem solving, attention, counting, and language.
• Brain scans allow the doctor to look at a picture of the brain to see if anything looks abnormal.

Information from the medical history and test results help the doctor rule out other possible causes of the person's symptoms. For example, thyroid problems, drug reactions, depression, brain tumours, and blood vessel disease in the brain can cause AD-like symptoms. Some of these other conditions can be treated successfully.

Recently, scientists have focused on a type of memory change called mild cognitive impairment (MCI). MCI can be conceived as being on a continuum between age-related memory decline and Alzheimer's disease. People with MCI have ongoing memory problems but do not have other losses like confusion, attention problems, and difficulty with language. In MCI, people have a 20% yearly possibility of converting to AD.

For a professional evaluation and diagnosis, call the Memory Line, tel. (021) 930 2177 or for referral to an appropriate mental health resource closest to you call the Mental Health Information Centre at tel. (021) 938 9229.