Brain shape changes as a potential early signal for dementia
A new study published in Nature Communications on September 29 reveals that the aging brain’s shape, not just its tissue loss, shifts in systematic ways that correlate with cognitive function. The research suggests that magnetic resonance imaging (MRI) can capture these geometric changes, which may help clinicians assess dementia risk earlier and with greater nuance than traditional measures alone.
Traditionally, researchers have focused on how much brain tissue is lost in specific regions or how cortical thickness changes over time. This study, however, looked at the brain’s spatial relationships and overall geometry across a large, diverse sample. The team analyzed more than 2,600 MRI scans from 1,059 adults ranging in age from 30 to 97 years. Their finding: the inferior and anterior regions tend to expand outward with age, while the superior and posterior regions shrink inward. Notably, these shape shifts were more pronounced in older adults who displayed signs of cognitive decline.
What the shape tells us about brain function
The researchers observed a striking pattern: individuals with stronger posterior compression showed poorer reasoning abilities. This link between geometry and function held up in two independent datasets, reinforcing the idea that brain shape changes are a reliable feature of aging rather than a random variation. By focusing on how regions move relative to one another, the study provides a broader view of brain aging and its impact on cognition.
A particularly compelling implication centers on the entorhinal cortex, a small memory hub tucked in the medial temporal lobe. The study authors propose that gradual angular shifts in brain shape could press this vulnerable region against the skull’s rigid base. Since the entorhinal cortex is one of the first areas to accumulate tau, a toxic protein associated with Alzheimer’s disease, this mechanical interaction could contribute to disease risk. As co-author Michael Yassa noted, understanding how aging-related shape changes might squeeze the entorhinal cortex “offers a whole new way to think about the mechanisms of Alzheimer’s disease and the possibility of early detection.”
From volumes to geometry: a new biomarker approach
These findings expand the toolkit for studying aging and dementia. While volumetric measures and cortical thickness remain valuable, geometry-based markers capture how the brain’s regions relate spatially to one another—information that appears to reflect both normal aging and disease processes. The study’s authors hope that temporal tracking of brain shape changes could serve as a complementary biomarker for identifying individuals at higher risk for cognitive impairment long before overt symptoms emerge.
The implications extend beyond understanding disease mechanisms. If future longitudinal work confirms that specific shape trajectories predict cognitive decline, clinicians could integrate geometry-based assessments into routine imaging analyses. This could enable earlier interventions, potential monitoring of treatment responses, and better-targeted strategies to slow or prevent dementia progression.
In sum, the research invites a shift in thinking about brain aging. Rather than viewing aging as a static loss of tissue, scientists are beginning to chart how the brain’s overall geometry evolves, and how those changes map onto cognitive function and disease risk. While more work is needed to translate these geometric markers into clinical practice, the study marks a significant step toward unraveling the physical underpinnings of dementia and unlocking earlier detection opportunities.
