Doing shift work for many years may dull the mind, according to new research.
The study, led by Jean-Claude Marquie, research director at the National Center for Scientific Research at the University of Toulouse, shows that people who work non-standard hours for more than 10 years suffered a 6.5 year decline in memory and thinking skills which lasted at least five years, although it did not prove shift work caused these changes.
The study tracked the mental abilities of more than 3,000 people from different regions in France who were employed in a wide range of sectors or who had retired.
The researchers evaluated the study participants in 1996, 2001 and 2006. More than 1,000 had done rotating shift patterns that switch between mornings, afternoons and nights.
In general, shift workers had lower memory, thinking and processing speed scores than people working standard hours, although the difference was not dramatic. Those working rotating shifts scored lower than other shift workers, particularly those who had done rotating shifts for 10 years or more.
The findings are published in Occupational and Environmental Medicine.