A new UCLA study has found a connection between how quickly the brain ages and the bacteria and chemical byproducts found in the gut, offering a fresh clue into what drives brain aging long before symptoms appear.
Researchers have long used brain scans to estimate a person's “brain age,” a measure that can differ from someone's actual age in years. When a brain looks older than expected on a scan, it has been linked in prior research to poorer memory, thinking skills and mood. However, most of these studies occurred among older adults or people with existing brain diseases. Whether this gap between brain age and chronological age means anything in younger, generally healthy people has been unclear.
In a new study published in the journal eBioMedicine, UCLA Health researchers analyzed brain scans from nearly 1,500 adults across three separate groups using a method that measures how different regions of the brain communicate with one another while at rest. They then built a computer model that estimated each person's age based on these communication patterns and calculated the difference between that estimate and the person's real age, a value they called the Brain Aging Index (BAI).
Across all three groups, people whose brains looked older than expected tended to score worse on tests of working memory and executive function, or skills related to focus and organization. They also reported more symptoms of depression. These patterns consistently involved brain regions linked to memory and self-referential thought.
In one study group, researchers also analyzed stool samples to look for connections between brain aging and gut biology. They found that a higher Brain Aging Index was associated with specific gut bacteria and metabolic byproducts, including certain fat molecules, a cholesterol-related compound and lower levels of a hormone called estetrol. The biological pathways involved pointed to the immune system, blood vessel function, communication between brain cells and cellular energy production.
“Brain aging doesn’t suddenly begin when we get older but the biological signals may be detectable decades earlier," said the study’s senior author Dr. Arpana Church, co-director of the Goodman-Luskin Microbiome Center at UCLA Health. “By linking these early brain changes with the gut microbiome and its metabolites, we are beginning to identify pathways that could ultimately help us understand who may be at risk and, importantly, where we might intervene to support healthier brain aging. This ultimately opens the door to exploring whether targeting gut health could one day support healthier brain aging.”
Church said these findings could eventually help identify people at higher risk for cognitive or mood-related decline earlier in life, and point to the gut as a potential target for future interventions aimed at supporting brain health and prevention earlier in life.
