EMBARGOED FOR RELEASE UNTIL 4 PM ET, August 26, 2026
Reduced brain volume may act as a clock for progression to early-onset dementia
EMBARGOED FOR RELEASE UNTIL 4:00 P.M. ET, WEDNESDAY, AUGUST 26, 2026
MINNEAPOLIS — In people diagnosed with early-onset Alzheimer’s
disease, a biomarker tool that detects shrinkage of the brain’s gray matter may
predict how quickly someone may progress from mild cognitive impairment (MCI) to
dementia, according to a new study published August 26, 2026, in Neurology®, an official
journal of the American Academy of Neurology.
Early-onset Alzheimer’s disease develops before age 65,
while people are still working or raising families. It begins with mild cognitive
impairment, thinking and memory problems that are greater than normal aging but
not severe enough to be diagnosed as dementia. It often progresses quickly to dementia,
but the timeline varies widely from person to person.
“This is a
study driven by one of the most frequent questions we get from patients in the
clinic: ‘When will I lose my independence?” said study author Alexandra Touroutoglou, PhD,
of Harvard Medical School in Boston, Massachusetts. “There are limited ways to
predict the transition from MCI to dementia, so we developed a brain scan biomarker
called the early-onset Alzheimer’s disease signature, a map that can be applied
to brain scans to measure shrinkage in regions of the brain involved in
thinking such as memory, language and reasoning. Our study found that brain
shrinkage measured by our biomarker can act as a timer for predicting when
dementia will start and how quickly someone progressed from MCI to dementia.”
The early-onset Alzheimer’s disease signature biomarker includes
a set of brain regions that show greater atrophy in people with the disease than
in people without the disease.
The study included data from 130 people who lived
independently with mild cognitive impairment and 97 healthy participants. They were
all between ages 40 and 64. Participants had magnetic resonance imaging brain
scans at the start of the study and at least one annual follow-up visit.
Researchers applied the brain scan biomarker to each
participant’s brain scan to measure shrinkage in eight key brain areas involved
in thinking and memory, including the medial and lateral parietal cortex as
well as the posterior lateral temporal cortex.
They calculated average thickness of each brain region and then
combined those measurements into an overall score for brain shrinkage.
Participants were followed for an average of two years. Approximately
65% of people with early-onset Alzheimer’s disease progressed from MCI to
dementia.
Researchers found that greater gray matter shrinkage on brain
scans as detected by the biomarker predicted faster progression to dementia. A
person’s risk of progression from MCI to dementia was 1.24 times higher for every
one standard deviation greater magnitude of shrinkage.
The biomarker was better at predicting progression than looking
only at people’s symptoms at the beginning of the study.
“Better tools are needed to predict when someone with early-onset Alzheimer’s disease may lose independence
and progress from MCI to dementia,” said Touroutoglou. “This brain scan biomarker
we developed may help predict how quickly the disease will progress in each
individual, giving physicians, people with early-onset Alzheimer’s disease and
their families better information about what to expect and allowing earlier clinical
trial enrollment for treatments that may improve outcomes.”
A limitation of the study was that the brain scan biomarker
was developed and tested in one group, most of whom were non-Hispanic white
people, so it is unclear how well it may work when applied to other populations.
The study was supported by the National Institutes of Health
and the Alzheimer’s Association.
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