Scientists have determined that how the brain shape changes with age could indicate early signs of dementia.

Experts are finding that the optimal approach to comprehend how the brain ages is not by scrutinizing its individual parts, but by examining the overall structure and the interaction between its various regions.

Researchers from Irvine, California, and Tenerife, Spain, conducted a comprehensive study using brain scans to measure these shape changes. They observed that as individuals age, the brain’s shrinkage is not uniform; instead, it adopts specific shape alterations.

The lower sections of the brain, responsible for vital functions like breathing and heartbeat, along with the frontal areas, integral to certain cognitive functions, tend to expand outward.

The top parts, crucial for language functions, and the back parts, involved in visual processing and motor control, tend to compress inward.

The distance between matching areas on the left and right sides of the brain, especially in the front, also increases.

The physical separation of the brain’s hemispheres serves as a potent indicator of diminished communication and coordination between the left and right sides. A weakened connection between hemispheres results in a less efficient brain network.

These particular changes in shape, validated across various groups, were directly associated with diminished cognitive abilities, such as reasoning, highlighting them as clear physical markers of cognitive decline.

Scientists now believe the key to understanding brain aging lies in studying its overall structure and the interactions between regions, rather than analyzing individual parts in isolation (stock)

As the US population continues to skew older, rates of dementia in the US are projected to balloon in the coming years, with the current estimate that cases will rise from the current seven million to nearly 13 million by 2060. 

A normal facet of aging is gradual brain shrinkage. On average, the brain shrinks by about 0.2 percent per year after 60. By the time a person reaches 80, their brain may be about 10 to 15 percent smaller than it was in their 30s.

Dr Niels Janssen, the senior author of the study and a professor at Universidad de La Laguna in Tenerife, Spain, said: ‘Most studies of brain aging focus on how much tissue is lost in different regions.

‘What we found is that the overall shape of the brain shifts in systematic ways, and those shifts are closely tied to whether someone shows cognitive impairment.’

To uncover how the brain’s shape changes with age, the researchers conducted a massive brain mapping project. 

They started with a vast dataset of over 2,600 brain scans from adults ages 30 to 97, some of whom have dementia. They used one large set of scans as their main test group and a second, completely independent set to double-check their results.

They measured the brain’s geometry, both its shape and form, in two ways. First, they looked at the brain’s global shape by virtually placing 400 points on its outer surface.

They then measured the distances between matching points on the left and right sides, creating a detailed map of where the brain was expanding or compressing.

This analysis measured the physical separation between matching areas of the left and right brain. Part A shows that this separation increases with age, most dramatically in the brain’s temporal and frontal lobes. Part B reveals that this pulling apart starts early in deep brain regions, spreads to the front and back of the brain in middle age, and is eventually accompanied by a squeezing together in a specific parietal area in the oldest groups

Second, they measured the distance between specific partner regions in the left and right hemispheres. Finally, they connected these physical measurements to real-world function.

Using advanced statistics, they tested whether these patterns of expansion and compression were linked to the participants’ age, their performance on memory and reasoning tests and whether they had ever been diagnosed with a cognitive issue. 

This allowed them to see not just how the brain changes shape, but how those specific changes might affect a person’s cognitive abilities.

The aging brain undergoes a specific and dramatic reshaping, not just an overall shrinkage. Particular patterns of expansion and compression were strongly linked to people’s brain health.

Memory problems were linked to expansion in temporal lobe regions, commonly known as the memory centers. One of the study’s most striking findings involves the entorhinal cortex, a vital hub for memory in the medial temporal lobe.

The research suggests that age-related brain reshaping may physically squeeze this fragile region against the base of the skull. 

Since this area is also where toxic tau protein first builds up in Alzheimer’s, the team proposed that these mechanical and gravitational forces could be a previously unknown reason for its extreme vulnerability.

Dr Michael Yassa, co-author of the study and a neurobiologist at the University of California, Irvine, said: ‘This could help explain why the entorhinal cortex is ground zero of Alzheimer’s pathology.

Part A in the graphic reveals that in people with clinical impairment (like dementia), their brains have both a strong ‘pulling apart’ in memory regions (red) and a unique ‘squeezing together’ in posterior areas (blue) that is not seen in normal aging. Part B shows that different cognitive issues have their own geometric ‘fingerprint.’ Poor Memory is linked to the memory centers stretching apart. Poor Executive Function (planning/reasoning) is tied to the brain’s posterior regions compressing. Poor Working Memory is associated with widespread compression across the brain’s lateral surfaces

‘If the aging brain is gradually shifting in a way that squeezes this fragile region against a rigid boundary, it may create the perfect storm for damage to take root. Understanding that process gives us a whole new way to think about the mechanisms of Alzheimer’s disease and the possibility of early detection.’

Poor executive function, which includes planning and reasoning, was linked to compression in parietal regions, areas for integrating information and vision.

The patterns seen in people with clinical impairment, such as a dementia diagnosis, were even more pronounced than in healthy aging, suggesting this reshaping accelerates with disease.

Janssen said: ‘This isn’t just about measuring brain shrinkage. It’s about seeing how the brain’s architecture responds to aging and how that architecture predicts who is more likely to struggle with memory and thinking.’

The conclusion that the brain’s geometry could serve as a biomarker for dementia marks a paradigm shift in the diagnostics of Alzheimer’s disease and the other forms of dementia that involve shrinkage in the hippocampus and frontal cortex.

Their findings were published in the journal Nature Communications. 

The sagging of certain parts of the brain could be detectable long before massive cell death occurs. 

A routine MRI could be analyzed to detect this. A specific pattern of expansion and compression could flag a patient as high-risk years before memory tests show a clear problem.

A neurologist can examine a map of a patient’s brain and identify a pattern that is highly specific to Alzheimer’s, such as strong temporal lobe expansion paired with parietal compression, versus a pattern indicative of another disorder, leading to more accurate diagnoses and targeted treatment plans.