Friday, January 18, 2008


Alzheimer's disease (AD), also called Alzheimer disease, and simply known as Alzheimer's, is a neurodegenerative disease that, in its most common form, is found in people over the age of 65. Approximately 24 million people worldwide have dementia of which the majority (~60%) is due to Alzheimer's.

Clinical signs of Alzheimer's disease are characterized by progressive cognitive deterioration, together with declining activities of daily living and by neuropsychiatric symptoms or behavioral changes. It is the most common type of dementia. Plaques which contain misfolded peptides called amyloid beta (Aß) are formed in the brain many years before the clinical signs of Alzheimer's are observed. Together, these plaques and neurofibrillary tangles form the pathological hallmarks of the disease. These features can only be discovered at autopsy and help to confirm the clinical diagnosis. Medications can help reduce the symptoms of the disease, but they cannot change the course of the underlying pathology.

The ultimate cause of Alzheimer's is unknown. Genetic factors are clearly indicated as dominant mutations in three different genes that account for the small number of cases of familial, early-onset AD have been identified. For the more common form of late onset AD, ApoE is the only clearly established susceptibility gene. All four genes can contain mutations or variants that confer increased risk for AD, but account for only 30% of the genetic picture of AD. These four genes have in common the fact that mutations in each lead to the excessive accumulation in the brain of Aß, the main component of the senile plaques that litter the brains of AD patients.

Although the origin of the concept of dementia goes as far back as the ancient Greek and Roman philosophers and physicians; it was in 1901 when Alois Alzheimer, a German psychiatrist, identified the first case of what became known as Alzheimer's disease. The patient was a 50-year-old woman called Auguste D. Alois Alzheimer followed her until she died in 1906, when he first reported the case publicly. In the following five years eleven similar cases were reported in the medical literature; some of them already using the term Alzheimer's disease. However the official consideration of the disease as a distinctive entity is attributed to Emil Kraepelin, who included "Alzheimer’s disease" or presenile dementia as a subtype of senile dementia in the eighth edition of his Textbook of Psychiatry, published in 1910.

Accordingly; for most of the twentieth century, the diagnosis of Alzheimer's disease was reserved for individuals between the ages of 45 and 65 who developed symptoms of dementia. The terminology changed after 1977 when a conference held in that year concluded that the clinical and pathological manifestations of presenile and senile dementia were almost identical, although the authors also added that this did not rule out the possibility of different etiologies. This eventually led to the use of "Alzheimer's disease" independently of onset age of the disease. However, the term senile dementia of the Alzheimer type (SDAT) was often used for a time to describe the condition in those over 65, with classical Alzheimer's disease being used for those younger. Eventually, the term Alzheimer's disease was formally adopted in medical nomenclature to describe individuals of all ages with a characteristic common symptom pattern, disease course, and neuropathology.