Alzheimer's could be revealed by a blood test a decade before symptoms appear, according to a new study.
A protein called GFAP is a possible marker for early stage Alzheimer's, according to researchers at the Karolinska Institutet in Sweden. Their findings indicate the protein could be a blood-marker seen about 10 years before symptoms emerge.
Alzheimer's is a brain disease that develops gradually, beginning decades before key symptoms like memory loss are experienced. Scientists believe GFAP could indicate changes in the brain before other signs develop.
At present, the neurodegenerative disease causes 60 to 70 percent of all dementia cases, according to the Swedish Brain Foundation. Diagnosing Alzheimer's early boosts the chance of slowing the disease with drugs.
The brain begins to change 20 to 25 years before patients start to notice memory loss and other cognitive symptoms, and the earlier they are diagnosed the faster they can access treatment.
Proteins beta-amyloid and tau begin to accumulate abnormally, causing the nerves in the brain to degenerate. As more brain neurons are damaged, suffers begin to lose cognitive functions such as memory and speech.
Writing in the journal Brain, study author Caroline Graff, professor at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet: "The first change we observed was an increase in GFAP (glial fibrillary acidic protein) approximately ten years before the first disease symptoms.
"This was followed by increased concentrations of P-tau181 and, later, NfL (neurofilament light protein), which we already know is directly associated with the extent of neuronal damage in the Alzheimer brain. This finding about GFAP improves the chances of early diagnosis."
The team searched biomarkers in the blood for very early pathological changes in a rare and inherited form of Alzheimers, where those who have a parent with the disease have a 50 percent chance of developing it.
They analysed 164 blood plasma samples from 33 mutation carriers, and 42 relatives without the inherited chance of getting Alzheimers taken between 1994 and 2018.
They found distinct changes of several blood protein concentrations in the mutation-carriers.
"Our results suggest that GFAP, a presumed biomarker for activated immune cells in the brain, reflects changes in the brain due to Alzheimer disease that occur before the accumulation of tau protein and measurable neuronal damage," said the study's first author Charlotte Johansson, a doctoral student at the Karolinska Institutet's Department of Neurobiology, Care Sciences and Society.
"In the future it could be used as a non-invasive biomarker for the early activation of immune cells, such as astrocytes in the central nervous system, which can be valuable to the development of new drugs and to the diagnostics of cognitive diseases."
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