Shift work, like chronic jet lag, is known to disrupt the body's internal clock (circadian rhythms), and it has been linked to a range of health problems, such as ulcers, cardiovascular disease, metabolic syndrome, and some cancers.
But little is known about its potential impact on brain function, such as memory and processing speed.
The researchers therefore tracked the cognitive abilities of more than 3000 people who were either working in a wide range of sectors or who had retired, at three time points: 1996; 2001; and 2006.