Synonyms in a broader sense
Alzheimer’s disease, dementia, Alzheimer
Alzheimer’s dementia is a degenerative brain disease that leads to dementia. The reasons for the decline in brain function (degeneration) are the loss of nuclei of the central nervous system, which produce messenger substances (transmitters), and tissue loss (atrophy) of the cerebral cortex. At the same time, there is an excessive deposition of certain substances in the brain and brain vessel walls.
Alzheimer’s disease is considered the most common cause of dementia in western nations and is responsible for 50-75% of all dementias. In Asian countries, on the other hand, another form of dementia, vascular dementia, seems to be more common than Alzheimer’s type dementia in contrast to Europe and the USA. The frequency of the disease depends on age.
It is about 0.04% in the age group under 60, about 1% up to the age of 70, about 3% between 70 and 79 and about 10% between 80 and 90. There are various data in different sources on the over 95-year-olds: On the one hand it is reported that the frequency decreases again at this age, 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 65 suffer from dementia, 50-75% of them from Alzheimer’s dementia.
The main age of onset of the disease is between 70 and 80 years of age. Women fall ill comparatively more often, but probably only because their share in this age group is much larger than that of men. The rare, familial form has a younger age of onset.
Morbus Alzheimer 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 a conspicuous memory weakness at an early age, which was associated with disorientation and hallucinations and led to her death at the age of 55 in 1906.
Alzheimer’s examined her brain after her death and discovered some abnormalities: The cerebral cortex was thinner than normal and he found heart-shaped deposits called “Alzheimer plaques and fibrils”. In the following five years, further cases of patients with similar diseases were already described in the medical literature as “Alzheimer’s disease”. The official name goes back to the psychiatrist Emil Kraepelin, with whom Alzheimer worked for several years.
In 1910 he named the disease after Alois Alzheimer in his “Textbook of Psychiatry”. Genetic factors 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 together as familial Alzheimer’s dementia (FAD). In some of these cases, Alzheimer’s disease is caused by a dominant hereditary genetic defect. The defective genes are located on chromosomes 1, 14 and 21, while the mutations on chromosomes 1 and 14 affect the genes of presenilin proteins.
If presenilin-1 on chromosome 14 is affected, the disease starts before the age of 60, in the extreme form 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 on chromosome 1 is affected, the age of onset of the disease is between 45 and 73 years.
Both proteins are related to the cleavage of protein-containing deposits in the tissue (amyloid). Mutations of the amyloid precursor protein (amyloid precursor protein (APP)) on chromosome 21 lead to the onset of the disease before the age of 65. Within the group of Alzheimer’s dementia caused by genetic defects, a mutation on chromosome 14 can be found in 80% of patients, in 15% on chromosome 1 and in 5% on chromosome 21.
In trisomy 21, dementia is the rule for those over 30 years of age, and very similar changes in the brain can be detected as in Alzheimer’s dementia. A defect in the gene of apolipoprotein-E on chromosome 19 can also be the cause of Alzheimer’s dementia, as the apolipoprotein-E reacts with amyloid and thus accelerates the accumulation (aggregation) of amyloid to the plaques. It is also associated with certain neurological symptoms that can occur in Alzheimer’s patients.