TUESDAY, Nov. 4, 2014 (HealthDay News) -- Working non-standard hours -- "shift work" -- for many years is not only hard on the body, but may also dull the mind, new research suggests. According to the study, published online Nov. 3 in Occupational & Environmental Medicine, those who do shift work for more than 10 years seem to have the equivalent of an extra 6.5 years of age-related decline in memory and thinking skills.
Jean-Claude Marquie, Ph.D., of the National Center for Scientific Research at the University of Toulouse in France, and colleagues tracked the mental abilities of 3,232 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. The men and women were aged 32, 42, 52, and 62 when they took the first set of tests to gauge memory, processing speed, and overall thinking ability. About half of the study participants (1,484) had done shift work at least 50 days of the year. More than 1,000 current and retired employees worked a rotating shift pattern that switched back and forth among morning, afternoons, and nights.
Overall, shift workers had lower memory, thinking, and processing speed scores than those who had worked only standard hours, the investigators found. Those who worked a rotating shift had lower overall memory and thinking ability scores compared to those who never did shift work. Those who had done rotating shift work for 10 years or more had even lower scores. The differences weren't dramatic, but they were evident, the authors noted. For instance, on the global cognitive performance score, those who never did shift work scored 56 points out of a possible 100, while those who worked rotating shifts for more than 10 years scored 51.8. It took at least five years for workers to recover mental skills, except for processing speed.
"Our work suggests that shift work is associated with impaired cognition, that the association is stronger and especially significant for exposure durations exceeding 10 years, and finally, and maybe most importantly, that the effect persists after having ceased any form of shift-work schedule," Marquie told HealthDay.
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