Although doctors do not know the exact cause of Alzheimer’s disease, some believe a blood protein may be an early predictor.

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Researchers from health institutions in Germany recently conducted a study, published in the Nature Medicine journal, to explore blood tests that could best predict the illness.

To do so, they examined 405 individuals from an international research collaboration, which assesses families with a rare form of Alzheimer’s associated with a particular gene mutation. For several years, they took blood samples from the subjects to test their level of neurofilament concentration, a type of protein in the blood that transports substances throughout the brain. The participants also had to complete cognition tests of memory and thinking skills.

The investigations were carried out for about 16 years.

After analyzing the results, the team noticed changes in the neurofilament concentration and found there was a link between the protein and brain degradation or memory decline and thinking.

In fact, they discovered those at risk of developing the disease had higher levels of the protein early on. Furthermore, the neurofilament concentration levels in both the blood and spinal fluid were increasing for those patients long before they showed signs of memory decline.

The scientists noted the test was only used on people with the particular form of Alzheimer’s. Therefore, they hope to yield the same results for those with more common forms of the disease.

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