Working shift hours can too early age the brain and dull intellectual capability, experts warn.
Their study, in the Environmental and occupation Medicine Journal, advised a decade of shifts aged the brain by more than 6 years.
There are some improvements after people prevented working harmful shifts, but it look 5 years to get back normal.
Professionals say the findings could be vital in dementia, as many patients have disordered sleep.
The body internal clock is made for us to be active in the daylight hours and asleep at night.
The destroying affects on the body of working against the body clock, from obesity and breast cancer, are well known.
Now a team at the Swansea University and the Toulouse University has shown an impact on the mind as well.
3 thousand people in France take part in memory test, large cognitive ability and speed of thought.
The brain generally declines as we age, but the experts said working antisocial shifts go faster the process.
The perfect news is that when people in the study quit shift job, their brains did get better, even if it took 5 years.
Dr Michael Hasting, from the Medical Research Council UK told the BBC: “The reversibility is truly amazing finding because no-one else has shown it and no issue how compromised a person may be there forever hope of improvement.”
He said the findings may have vital consequences in dementia, which is known to destroy sleeping patterns in a similar way to shift job.
Prof Drek-Jan from Center of Surgery Sleep cautioned that leaved shift employees still had lower sleep standard than persons who had never done rights.
“Some of these affects may not be so rapidly or readily reserved.”
He included: “We now admit that shift job may not be perfect for your physical health, but this show your brain work is affected, and I think that findings will shock many people.”
Dr Philip Tucker, part of the Swansea research team, told: “it was quite a substantial decrease in brain work, it is likely that when people trying to undertake difficult cognitive jobs then they might make more problems and slip-ups, may be one in hundred makes a mistake with a very big consequence, but it difficult to say how large a difference it would make in day-to-day life.”