Alzheimer's disease, dementia, Alzheimer's
Alzheimer's disease is a degenerative brain disease that leads to dementia. The reasons for the decline in brain function ( degeneration ) are the destruction of central nervous system nuclei, which produce messenger substances ( transmitters ), and the tissue atrophy ( atrophy ) of the cerebral cortex. At the same time, there is an excessive deposition of certain substances in the brain and cerebral vascular walls.
Alzheimer's disease is the leading cause of dementia in Western nations and accounts for 50-75% of all dementias. In contrast, in contrast to Europe and the US, another form of dementia, vascular dementia, appears to be more common in Asian countries than dementia of the Alzheimer type.
The frequency of the disease is age-dependent. It is about 0.04% in the age group less than 60 years, about 1% up to the age of 70, about 3% between 70 and 79 years and about 10% between 80 and 90 years. Among the over 95-year-olds, there are various statements in different sources: On the one hand, it is reported that the incidence at this age decreases again, on the other hand it is claimed that 40-50% are ill. In general, however, it can be said that about 5% of all people over the age of 65 suffer from dementia, 50-75% of them with Alzheimer's disease.
The main disease age is between the 70th and 80th year of life. Women are relatively more likely to become ill, but probably only because their share of this age group is much larger than that of men. The rare, familial form has a younger age of onset.
In a patient with trisomy 21 ("Down Syndrome"), the risk of Alzheimer's disease is many times higher. See also Alzheimer's causes
Alzheimer's disease was first described in 1901 by the German physician Alois Alzheimer ( 1864-1915 ) as a "peculiar clinical picture". The patient he described was the then 51-year-old Auguste Deter. She had an early onset of memory deficiency associated with disorientation and hallucinations, leading to her death at the age of 55 in 1906. Alzheimer examined her brain after her death and discovered some abnormalities: The cerebral cortex was thinner than normal and he found herd-shaped deposits, the "Alzheimer's plaques and fibrils".
Over the next five years, other cases of patients with similar disease have been described as "Alzheimer's disease" in the medical literature. The official name goes back to the psychiatrist Emil Kraepelin, with whom Alzheimer worked together for several years. He named the disease in 1910 in his "textbook of psychiatry" after Alois Alzheimer.
Genetic factors also play a role as further causes of Alzheimer's disease. In 7% of all patients with Alzheimer's disease, there is a familial accumulation of dementia. These patients are grouped into familial Alzheimer's disease (FAD). In some of these cases, Alzheimer's disease is caused by a dominant inheritable genetic defect. The defective genes are located on chromosomes 1, 14 and 21.
The mutations on chromosome 1 and 14 concern the genes of the presenilin proteins. If presenilin-1 is affected on chromosome 14, the disease begins before the 60th, in its extreme form even before the age of 30. A mutation of the presenilin-1 gene is the most common cause of familial Alzheimer's dementia with early onset.
If presenilin-2 is affected on chromosome 1, the age of onset is between the ages of 45 and 73 years. Both proteins are related to the cleavage of proteinaceous deposits in the tissue ( amyloid ). Mutations of the precursor protein of amyloid (amyloid precursor protein (APP)) on chromosome 21 lead to onset before the age of 65.
Within the group of Alzheimer dementia caused by genetic defects, 80% of patients have a mutation on chromosome 14, 15% on chromosome 1 and 5% on chromosome 21.
In trisomy 21, dementia is the rule among those over the age of 30, and similar changes in the brain as in Alzheimer's disease can be detected.
A defect in the gene of apolipoprotein-E on chromosome 19 may also be the cause of Alzheimer's disease, as apolipoprotein-E reacts with amyloid, thus accelerating the accumulation of amyloid into the plaques. It is also associated with certain neurological symptoms that can occur in Alzheimer's patients.