You may be 40 years old, but could your brain already be showing signs of accelerated aging? New research involving more than 18,000 people suggests that the answer may depend on much more than genetics or your date of birth.

by individual habits but also by pollution, social inequality, living conditions, and other environmental exposures.

So what exactly causes the

brain to age faster—and can anything be done to protect it?

What Does It Mean When Scientists Say Your Brain Is Aging Faster?

Your chronological age is simply the number of years you have been alive.

Your brain’s estimated biological age is more complicated.

Researchers use brain imaging, electrical activity, and computational models to investigate patterns associated with normal aging.

These measurements may include changes in brain volume,

tissue structure,