Alzheimer's Disease

Alzheimer's disease is a degenerative disorder that attacks the brain and leads to dementia and is one of the most common dementing disorders of old age. Alzheimer's affected nearly 4 million individuals in the U.S. alone. Dementia is a group of symptoms characterized by an insidious decline in intellectual functioning of sufficient severity to interfere with normal daily activities and social relationships. Cognitive ability is the most serious aspect of the loss in intellectual functioning. Dementia of Alzheimer's disease is distinguished from age-associated memory impairment and benign forgetfulness in that it is inevitably marked by progressive, irreversible declines in memory, performance of routine tasks, time and space orientation, language and communication skills, abstract thinking, and the abilities to learn, carry out mathematical calculations, and construct an object with blocks. Alzheimer's disease is also characterized by personality changes and impaired judgment.

Because the symptoms of dementia appear later in life, its signs and symptoms have been mistaken for indicators of old age. In recent years, scientists have learned more about the aging process and it has become clear that the aging process does not, by itself, lead to dementia or neurodegenerative disease. Alzheimer's and other dementing disorders of old age are caused by specific pathological conditions. In the absence of disease, the human rain can and does continue to function unimpaired.

Aging does not cause dementia or Alzheimer's but, it is most strongly associated as a risk factor for Alzheimer's disease. Another important risk factor is family history or genetic predisposition. The history of AD in a primary family member (parent or sibling) increases the odds of developing AD. A history of severe head injury that leads to brief loss of consciousness doubles the risk of developing AD. These three risk factors meet the accepted epidemiological criteria for causal factors. The first being that they provide a plausible biological explanation and second being that their affects are strong and consistent. Other risk factors that have been investigated, such as maternal age, hypothyroidism and exposure to environmental toxins, have not been shown to meet the criteria.

AD is a distinct disease that is defined by its characteristic clinical course and pathology, although, it is a heterogeneous condition with varied manifestations. The characteristic features of AD brain pathology differ among people as well as the rate of cognitive impairment. Though the onset, course and sequence of events may vary widely, it seems likely nonetheless that the destructive forces involved ultimately converge to cause neuron dysfunction, loss of connections between neurons, and the death of some neurons. Scientists are trying to discover the reason for why the neurons lose their ability to communicate with each other as well as the reasons for selective neuronal death, as well as their effort to discover the cause(s) of AD.

There are three interconnected systems of the brain that the survival of neurons in the brain depends on for proper functioning: communication, metabolic and repair. The communication system used by most neurons relies on an