A new UCLA study suggests that the pace of brain aging may be related to gut bacteria and the chemicals they produce. The findings offer a new look at biological changes that can begin long before noticeable problems with memory or thinking appear.
Scientists have used brain scans for years to estimate a person’s “brain age,” which can differ from chronological age. Previous research has found that when the brain appears older than expected, that pattern may be associated with poorer memory, weaker thinking skills and mood swings.
However, most previous studies focused on older adults or people who already suffered from neurological conditions. That left an important question unanswered: Is an older-looking brain also important in younger, generally healthy adults?
Measure brain age
In a new study published in the journal eBioMedicineUCLA Health researchers examined brain scans of nearly 1,500 adults divided into three separate groups.
The team used a scanning method that measures how different areas of the brain communicate with each other while a person is at rest. The researchers then created a computer model that estimated each person’s age based on those communication patterns.
They compared the estimated brain age with the actual age of each participant. The difference between the two became what the researchers called the Brain Aging Index (BAI).
Older-Looking Brains Linked to Memory, Mood
Across all three groups, participants whose brains appeared older than their chronological age generally performed worse on tests of working memory and executive function. Those skills help people hold information in mind, stay focused, plan, and organize.
People with a higher brain aging index also reported more symptoms of depression. The patterns repeatedly involved brain regions associated with memory and self-referential thinking, or the mental processes people use when thinking about themselves and their own experiences.
Gut Bacteria Offer Another Clue
For one of the study groups, the researchers also examined stool samples to see if differences in brain aging were related to changes in the gut.
They found that a higher rate of brain aging was associated with specific gut bacteria and various metabolic byproducts. These included certain fat molecules, a compound related to cholesterol, and lower levels of a hormone called estetrol.
Pathways connected to these biological signals involved the immune system, blood vessel function, communication between brain cells, and the processes cells use to produce energy.
Signs of brain aging may appear decades earlier
“Brain aging does not begin suddenly when we age, but biological signals may be detectable decades earlier,” said the study’s lead author, Dr. Arpana Church, co-director of the Goodman-Luskin Microbiome Center at UCLA Health. “By linking these early brain changes to the gut microbiome and its metabolites, we are beginning to identify pathways that could ultimately help us understand who may be at risk and, more importantly, where we might intervene to support healthier brain aging. Ultimately, this opens the door to exploring whether focusing on gut health could one day support healthier brain aging.”
Church said the findings could eventually help researchers identify people at higher risk of cognitive or mood-related declines earlier in life. They also raise the possibility that the gut could become a target for future strategies designed to support brain health and prevention earlier in life.