The same test may also identify neuro-degeneration in other brain diseases
Changes in the levels of a protein in the blood could help detect damage in the brain almost 16 years before the symptoms of Alzheimer's disease actually develop, according to a new study by scientists from the Washington University School of Medicine in St Louis, Missouri.
About 5.7 million people in the US currently suffer from Alzheimer's disease, and the number is estimated to increase to about 14 million by 2050, according to the US Alzheimer's Association.
Alzheimer's patients experience cognitive difficulties, decline in behavioural and physical abilities, and mood swings, and presently, there is no drug to stop the progression, or cure the condition.
Scientists have long known that people suffering from dementia show higher levels of a specific protein, named neurofilament light chain (NfL), which leaks into the cerebrospinal fluid after death of brain cells. It is, however, difficult to measure the levels of protein in the body without invasive spinal taps.
Now, scientists say they have developed the technique to detect NfL in the blood using a simple blood test.
In the current study, 405 people from the Dominantly Inherited Alzheimer's Network (DIAN) were recruited to be the participants of the study. Of them, 243 carried a rare genetic mutation that predisposed them to Alzheimer's, while 162 participants were found to be without such a mutation.
It was found that in people with early-onset genetic variant, symptoms of Alzheimer's developed at well-defined ages, allowing the team to measure their NfL levels a known number of years before symptoms were expected to become apparent.
It was also observed that protein levels were higher at baseline and increased over time for participants with the defective gene variant. In comparison, protein levels were low in people without faulty gene variant. This difference was noticeable almost 16 years before cognitive symptoms were expected to arise.
"Sixteen years before symptoms arise is really quite early in the disease process, but we were able to see differences even then," said Washington University graduate student Stephanie Schultz, one of the paper's co-first authors.
According to researchers, people with higher protein levels in the past were most likely to have signs of brain atrophy and decreased cognitive abilities when they revisited the clinic.
A commercial blood testing kit - similar to the one used in the study - is currently available to measure protein levels in the blood. However, the US Food and Drugs Administration has not yet approved the kit to predict an individual's risk of brain damage.
"I could see this being used in the clinic in a few years to identify signs of brain damage in individual patients," said Dr Brian Gordon, an assistant professor of radiology at Washington University and an author on the study.
"We're not at the point we can tell people, 'In five years you'll have dementia.' We are all working towards that."
The findings of the study are published in journal Nature Medicine.