As Shakespeare put it, we all have our entrances and our exits on this grand stage we call life, and now researchers have identified the specific point in middle-age when our brain cells show the first signs of starting down a downward slope.

That age, based on brain scans and tests covering 19,300 individuals, is on average around 44 years. It’s here that degeneration starts to be noticeable, before hitting its most rapid rate at age 67. By the time we reach 90, the speed of brain aging levels off.

According to the team behind the new study, led by researchers from Stony Brook University in the US, the findings could be helpful in figuring out ways to promote better brain health during the later stages of life.