MRI scans show brain changes linked to Alzheimer's up to seven years early

September 21, 2026 at 07:00 PM2 min

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MRI scans show that the thickness of the brain's outermost layer changes before the onset of Alzheimer's disease, detectable up to seven years prior, researchers reported August 19 in Nature Neuroscience. People who later developed high amyloid-beta levels had thicker cortices than those who did not, with differences of a few hundredths of a millimeter visible years before PET scans confirmed the protein buildup. The findings suggest the trajectory of cortical changes in early Alzheimer's is more complex than previously thought.

Key Facts

MRI scans from over 1,000 participants in long-term aging studies showed cortical thickness differences of a few hundredths of a millimeter up to seven years before high amyloid-beta levels were detected by PET scans.
People who later developed high amyloid-beta levels had thicker cortices than those who did not, and their cortices thinned less overall with age.
The findings were reported August 19 in Nature Neuroscience by Alzheimer's researcher Yunpeng Wang of the University of Oslo and colleagues.
No link was observed between cortical thickness and memory problems at this early stage of the disease.

Cortical Thickness Changes

Researchers compared changes in the thickness of the cortex, the brain's outermost layer averaging around 2.5 millimeters, between people who later showed high amyloid-beta levels and those who did not. People who went on to develop high amyloid-beta levels had thicker cortices than people who did not. Differences in thickness of a few hundredths of a millimeter were visible up to seven years before participants were deemed to have high amyloid-beta levels based on their PET scans. The cortices of people in both groups thinned naturally with age, but those of people who later developed high amyloid-beta thinned less overall.

Implications for Alzheimer's Research

The findings imply that the trajectory of cortical changes is not as simplistic as previously thought, according to Victor Montal, a degenerative diseases researcher at the Barcelona Supercomputing Center who was not involved in the work. Rather than assuming the cortex thins consistently due to atrophy as the disease progresses, researchers will need to account for slower thinning in the early stages when studying Alzheimer's, Montal said. The relative thickening of the cortex might come from inflammation that occurs as amyloid-beta first starts to accumulate, said Wang of the University of Oslo. MRIs cannot determine the cause of the thickening directly.