First of all, they struggle for words, do not remember anymore, and finally sink into oblivion: In Germany today, about 1.7 million people are considered to be suffering from dementia. About two-thirds of them have Alzheimer's, the most common form of dementia. As life expectancy increases, there are likely to be 3 million dementia patients in 2050.
Researchers have now developed a test that points to a possible Alzheimer's disease years before the first symptoms, they report in the journal "Nature Medicine". The test measures certain proteins that are produced when nerve cells die off.
"Normally, such proteins are rapidly broken down in the blood and are therefore not very well suited as markers," says Mathias Jucker of the German Center for Neurodegenerative Diseases (DZNE) and lead author of the study. A small piece of so-called neurofilament, however, proved to be remarkably resistant. It was already accumulating in the blood of Alzheimer's patients long before the first symptoms appeared.
Data evaluated by more than 400 people
Exactly on this protein the blood test is based. The study is based on data and samples from 405 individuals collected as part of an international research network - the Dominantly Inherited Alzheimer Network (DIAN). The network examines families in which Alzheimer's already occurs in middle age. Using genetic analysis, researchers can predict quite accurately if and when a family member will fall ill. Experts from the Hertie Institute for Clinical Brain Research (HIH), the University Hospital Tübingen and the Washington University School of Medicine were also involved in the study.
The international research team investigated how the filament concentration developed in the long term among those affected. The result: Up to 16 years before the onset of the first dementia symptoms, the researchers found significant changes in the blood of the patients. "It is not the absolute value of the filament concentration, but its temporal evolution, which is really meaningful and allows predictions about the further course of the disease," says Jucker.
Further tests showed that the concentration of neurofilaments is a measure of nerve cell death. "We were able to make predictions about the loss of brain mass and cognitive impairment that actually occurred two years later," says Jucker.
However, the test alone is not sufficient for an Alzheimer's diagnosis, because the filaments also accumulate in other diseases in the blood, for example in multiple sclerosis. In addition, it is still unclear whether the proteins can also predict Alzheimer's disease, if there is no family history.
"The test is a very accurate indicator of disease progression, making it an excellent tool to explore new Alzheimer's therapies in clinical trials," said Jucker. The disease of the brain is so far incurable. The currently available dementia drugs only slow the progression of the disease but can not stop it.
Dangerous protein deposits
Already two decades before dementia begins, the brain changes in Alzheimer's patients. For example, the pieces of protein accumulate beta-amyloid. These protein deposits are considered to be the main cause of Alzheimer's disease because they can destroy nerve cells, cause inflammation and disrupt the transmission of signals between nerve cells. Scientists had therefore developed a drug that these proteins should dissolve again. However, it has not stopped dementia (read more here).
"The fact that there is still no effective treatment for Alzheimer's is probably related to the fact that the previous therapies are much too late," says Jucker. In such cases, the blood test could help.
However, outside of clinical trials, the test should not be used. First, because he does not provide a reliable diagnosis. On the other hand, only very few people would probably want to know years in advance that they are suffering from Alzheimer's - at least as long as there is no cure.