A person’s “brain age” may be different from their chronological age. For years, scientists have used brain scans to estimate this age and found that when the brain appears older than expected, it is associated with a pattern of poorer memory, weaker thinking skills and changes in mood. Most of these studies focused on older adults who already had neurological conditions. But does the brain start to age faster in a generally healthy adult?According to a new study published in the journal eBioMedicine, bacteria present in the gut and the chemical compounds produced by them may be connected to brain ageing. UCLA Health researchers examined brain scans from nearly 1,500 adults divided across three separate groups.They used a scanning approach that measures how different areas of the brain communicate with one another when a person is at rest. Researchers then created a computer model that estimated each person’s age based on those communication patterns. They compared the estimated brain age with each participant’s actual age. The difference between the two became what the researchers called the Brain Ageing Index (BAI).
Older-looking brains linked to memory and mood shifts
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 abilities help people hold information in mind, stay focused, plan, and organise. They also reported more symptoms of depression. The patterns repeatedly involved brain regions associated with memory and self-referential thought, or the mental processes people use when thinking about themselves and their own experiences.For one of the study groups, the researchers also examined stool samples to see if differences in brain ageing were connected to changes in the gut. They found that a higher brain ageing index was associated with a specific gut bacterium and several metabolic byproducts. These included certain fat molecules, a cholesterol-related compound and lower levels of a hormone called estetrol. The pathways connected with 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 ageing may appear decades early
“Brain ageing 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 Centre 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 ageing. This ultimately opens the door to exploring whether targeting gut health could one day support healthier brain ageing.”Church said the findings may eventually help researchers identify people at greater risk of cognitive or mood-related decline early 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.