We often think about brain aging as something determined by genetics, health and lifestyle.
But there may be another important part of the picture:
the environment in which we live.
A large international study involving 18,701 people across 34 countries found that physical and social conditions were strongly associated with how old the brain appeared on brain imaging.
The findings suggest that healthy brain aging may depend on more than what we do as individuals.
Your Brain Does Not Age in Isolation
Throughout life, we are exposed to many different influences.
Some come from our physical surroundings. Others come from the social and economic conditions in which we live.
Scientists sometimes describe the combination of these influences as the exposome.
Instead of asking whether one particular environmental factor affects aging, researchers can therefore ask a broader question:
What is the combined effect of the environment surrounding us?
That is what researchers investigated in this study.
What Did Researchers Find?
The researchers examined 73 physical and social factors and compared them with measures of brain aging.
One finding stood out.
When multiple exposures were considered together, they were much more strongly associated with brain aging than when individual exposures were examined separately.
People living with a greater overall burden of unfavorable conditions were more likely to show accelerated brain aging.
Their brains appeared older on imaging than would be expected from their chronological age.
Physical and Social Environments May Affect the Brain Differently
The study also revealed an interesting pattern.
The physical environment was more strongly associated with changes in brain structure.
The social environment was more strongly associated with changes in how different areas of the brain communicate with each other.
This suggests that the environment may relate to brain aging through more than one pathway.
It also shows why looking at only one risk factor may give us an incomplete picture.
Why Is the Combined Environment Important?
In everyday life, exposures rarely occur one at a time.
We experience many conditions simultaneously and often for years or decades.
This study found that considering these exposures together provided substantially more information about brain aging than looking at individual factors separately.
That is an important idea for longevity medicine.
Aging is unlikely to be explained by one food, one supplement, one behavior or one environmental exposure.
It develops through the interaction of many influences over time.
Can Changing Your Environment Slow Brain Aging?
We do not know yet.
This study found strong associations, but it was observational.
That means it cannot prove that unfavorable environmental or social conditions directly cause the brain to age faster.
It also cannot prove that changing a particular exposure will make the brain age more slowly.
Further research will be needed to identify which environmental factors are genuinely causal and which can realistically be modified.
What Does This Mean for Healthy Aging?
The findings broaden the way we think about prevention.
Exercise, nutrition, sleep, smoking and cardiovascular health remain important for protecting the brain.
But healthy aging may not be determined entirely by personal choices.
The physical and social world around us may also be part of the biology of aging.
Understanding these influences could eventually help us develop more comprehensive strategies for protecting brain health throughout life.
