What is Alzheimer’s Disease?
Alzheimer’s disease (AD) is the most common form of dementia, a neurologic disease characterized by loss of mental ability severe enough to interfere with normal activities of daily living, lasting at least six months, and not present from birth. AD usually occurs in old age, and is marked by a decline in cognitive functions such as remembering, reasoning, and planning.
A person with AD usually has a gradual decline in mental functions, often beginning with slight memory loss, followed by losses in the ability to maintain employment, to plan and execute familiar tasks, and to reason and exercise judgment. Communication ability, mood, and personality may also be affected. Most people who have AD die within eight years of their diagnosis, although that interval may be as short as one year or as long as 20 years. AD is the fourth leading cause of death in adults after heart disease, cancer, and stroke.
Between two and four million Americans have AD; that number is expected to grow to as many as 14 million by the middle of the 21st century as the population as a whole ages. While a small number of people in there 40s and 50s develop the disease (called early-onset AD), AD predominantly affects the elderly. AD affects about 3% of all people between ages 65 and 74, about 19% of those between 75 and 84, and about 47% of those over 85. Slightly more women than men are affected with AD, but this may be because women tend to live longer, and so there are a higher proportion of women in the most affected age groups.
The cause of Alzheimer’s disease is unknown. Some strong leads have been found through recent research, however, and these have also given some theoretical support to several new experimental treatments.
AD affects brain cells, preferentially those in brain regions responsible for learning, reasoning, and memory. Autopsy of a person with AD shows that these regions of the brain become clogged with two abnormal structures, called neurofibrillary tangles and senile plaques. Neurofibrillary tangles are twisted masses of protein fibers inside nerve cells, or neurons. Senile plaques are composed of parts of neurons surrounding a group of brain proteins called beta-amyloid deposits. While it is not clear exactly how these structures cause problems, some researchers now believe that their formation is in fact responsible for the mental changes of AD, presumably by interfering with the normal communication between neurons in the brain.
What triggers the formation of plaques and tangles is unknown, although there are several possible candidates. Inflammation of the brain may play a role in their development. Restriction of blood flow may be part of the problem, perhaps accounting for the beneficial effects of oestrogen, which increases blood flow in the brain, among its other effects. Highly reactive molecular fragments called free radicals damage cells of all kinds, especially brain cells, which have smaller supplies of protective antioxidants thought to protect against free radical damage. Vitamin E is one such antioxidant, and its use in AD may be of possible theoretical benefit.
Several genes have been implicated in AD, including the gene for amyloid precursor protein, or APP, responsible for producing amyloid. Mutations in this gene are linked to some cases of the relatively uncommon early-onset forms of AD. Other cases of early-onset AD are caused by mutations in the gene for another protein, called pre-senilin. AD eventually affects nearly everyone with Down syndrome, caused by an extra copy of chromosome 21. Other mutations on other chromosomes have been linked to other early-onset cases.
Potentially the most important genetic link was discovered in the early 1990s on chromosome 19. A gene on this chromosome, called apoE, codes for a protein involved in transporting lipids into neurons. ApoE occurs in at least three forms, called apoE2, apoE3, and apoE4. Each person inherits one apoE from each parent, and therefore can either have one copy of two different forms, or two copies of one. Compared to those without ApoE4, people with one copy are about three times as likely to develop late-onset AD, and those with two copies are almost four times as likely to do so. Despite this important link, not everyone with apoE4 develops AD, and people without it can still have the disease. Why apoE4 increases the chances of developing AD is not known.
While the ultimate cause or causes of Alzheimer’s disease are still unknown, there are several risk factors that increase a person’s likelihood of developing the disease. The most significant one is, of course, age; older people develop AD at much higher rates than younger ones. Another risk factor is having a family history of AD, Down syndrome, or Parkinson’s disease. People who have had head trauma or hypothyroidism may manifest the symptoms of AD more quickly. No other medical conditions have been linked to an increased risk for AD.
Many environmental factors have been suspected of contributing to AD, but population studies have not borne out these links. Among these have been pollutants in drinking water, aluminum from commercial products e.g. deoderants, and mercury dental fillings. Further research may yet turn up links to other environmental culprits, although no firm candidates have been identified.
The symptoms of Alzheimer’s disease begin gradually, usually with memory lapses. Occasional memory lapses are of course common to everyone, and do not by themselves signify any change in cognitive function. The person with AD may begin with only the routine sort of memory lapse…forgetting where the car keys are…but progress to more profound or disturbing losses, such as forgetting that he or she can even drive a car. Becoming lost or disoriented on a walk around the neighbourhood becomes more likely as the disease progresses. A person with AD may forget the names of family members, or forget what was said at the beginning of a sentence by the time he hears the end.
As AD progresses, other symptoms appear, including inability to perform routine tasks, loss of judgment, and personality or behaviour changes. Some patients have trouble sleeping and may suffer from confusion or agitation in the evening (“sunsetting”). In some cases, people with AD repeat the same ideas, movements, words, or thoughts, a behaviour known as preservation. In the final stages people may have severe problems with eating, communicating, and controlling their bladder and bowel functions.
A list of ten warning signs of AD:
• Memory loss that affects job skills
• Difficulty performing familiar tasks
• Problems with language
• Disorientation of time and place
• Poor or decreased judgment
• Problems with abstract thinking
• Misplacing things
• Changes in mood or behaviour
• Changes in personality
• Loss of initiative
The person with Alzheimer’s disease will gradually lose the ability to dress, groom, feed, bathe, or use the toilet by himself; in the late stages of the disease, he may be unable to move or speak. In addition, the person’s behaviour becomes increasing erratic. A tendency to wander may make it difficult to leave him unattended for even a few minutes and make even the home a potentially dangerous place. In addition, some patients may exhibit inappropriate sexual behaviours.
The nursing care required for a person with AD is well within the abilities of most people to learn. The difficulty for many caregivers comes in the constant but unpredictable nature of the demands put on them. In addition, the personality changes undergone by a person with AD can be heartbreaking for family members, as a loved one deteriorates, seeming to become a different person. Not all AD patients develop negative behaviours: some become quite gentle, and spend increasing amounts of time in dreamlike states.
A loss of good grooming may be one of the early symptoms of AD. Mismatched clothing, unkempt hair, and decreased interest in personal hygiene become more common. Caregivers, especially spouses, may find these changes socially embarrassing and difficult to cope with. The caregiver will usually need to spend increasing amounts of time for grooming to compensate for the loss of attention from the patient, although some adjustment of expectations (while maintaining cleanliness) is often needed as the disease progresses.
Proper nutrition is important for a person with AD, and may require assisted feeding early on, to make sure the person is taking in enough nutrients. Later on, as movement and swallowing become difficult, a feeding tube may be placed into the stomach through the abdominal wall. A feeding tube requires more attention, but is generally easy to care for if the patient is not resistant to its use.
For many caregivers, incontinence becomes the most difficult problem to deal with at home, and is a principal reason for pursuing nursing home care. In the early stages, limiting fluid intake and increasing the frequency of toileting can help. Careful attention to hygiene is important to prevent skin irritation and infection from soiled clothing.
In all cases, a person diagnosed with AD should no longer be allowed to drive, because of the increased potential for accidents and the increased likelihood of wandering very far from home while disoriented. In the home, simple measures such as grab bars in the bathroom, bed rails on the bed, and easily negotiable passageways can greatly increase safety. Electrical appliances should be unplugged and put away when not in use, and matches, lighters, knives, or weapons should be stored safely out of reach. The hot water heater temperature may be set lower to prevent accidental scalding. A list of emergency numbers, including the poison control center and the hospital emergency room, should be posted by the phone.
Several substances are currently being tested for their ability to slow the progress of Alzheimer’s disease. These include acetylcarnitine, a supplement that acts on the cellular energy structures known as mitochondria. Gingko extract, derived from the leaves of the Gingko biloba tree, interferes with a circulatory protein called platelet activating factor. Gingko extract has been used for many years in China and is widely prescribed in Europe for treatment of circulatory problems. A 1997 study of patients with dementia seemed to show that gingko extract could improve their symptoms, though the study was criticized for certain flaws in its method. Gingko extract is available in many health food or nutritional supplement stores. Some alternative practitioners also advise people with AD to take supplements of phosphatidylcholine, vitamin B, and folic acid.