Blood Test Detects Alzheimer's Damage Before Symptoms

A study published in Nature Medicine details how a simple blood test can reliably identify brain damage in people with Alzheimer's before the onset of symptoms, reports Medical Xpress . The test detects neurofilament light chain, a structural protein that forms part of the internal framework of neurons; when brain neurons are damaged or dying, this protein leaks into the cerebrospinal fluid within the brain and spinal cord, and then into the bloodstream. The team examined more than 400 people, including 247 carriers of an early-onset genetic variant and 162 of their unaffected relatives. Participants with the faulty gene variant had protein levels that were higher at baseline and increased over time, while those with the healthy form of the gene exhibited low protein levels that generally did not change. This difference was identifiable 16 years before cognitive symptoms were expected to arise. Brain scans also showed how rapidly the protein levels rose in parallel with the speed with which the precuneus — a region of the brain related to memory — thinned and contracted. The researchers collected data on 39 people with disease-causing variants when they returned to the clinic an average of two years after their last visit. Persons whose blood protein levels had previously increased rapidly were most likely to manifest brain atrophy and diminished cognitive abilities when they revisited the clinic.