Alzheimer's disease may leave marks on the brain more than seven years before the first signs appear on a standard amyloid PET scan, according to a new study published in Nature Neuroscience. Researchers at the University of Oslo reached that conclusion by following healthy older adults with repeated MRI scans for nearly two decades.
Nearly 20 years of brain scans
The team tracked cognitively healthy older people with regular MRI imaging over about 20 years. Using that data, the researchers could pinpoint when, and in whom, amyloid plaques became detectable on PET scans. They then looked back at MRI images from the preceding years and compared brain changes in people who later developed plaques with those who did not. 'What is unique here is that we have examined changes in brain structure in the years before the first scan revealed plaques,' said Anders Martin Fjell, who led the study.
What appears before the plaques
The researchers found structural changes in the brain at least seven years before high levels of plaque became visible on PET scans. 'We found that structural changes in the brain occur many years before high levels of plaque are seen on PET scans, which is the brain scan currently used to identify the earliest signs of Alzheimer's disease,' said James Michael Roe, a co-author of the study. For years, amyloid PET has been treated as the earliest detectable sign of Alzheimer's. The new results suggest the disease process starts earlier and involves more than the buildup of plaques.
Why earlier detection matters
Alzheimer's remains very hard to treat, in part because it is closely tied to aging and is probably shaped by many factors. If imaging can flag the disease earlier, drug trials could start sooner, and treatments might target processes beyond amyloid. The findings also widen the search for early markers, pointing to structural change as a candidate signal. The authors describe the work as the earliest brain-imaging signal linked to Alzheimer's detected to date, and they say it may help scientists identify the disease years before symptoms appear.