Working an irregular shift pattern may be causing long-term damage to people’s memory and mental abilities, new research has shown. The study of employed and retired French workers suggested a decade of shifts aged the brain by more than six years.
Researchers from the universities of Toulouse and Swansea found a link between working shifts and a decline in brain function – especially among those whose shifts rotated between morning, afternoon and night. In the study of 3,232 employed and retired workers living in France, scientists found that those who worked rotating shifts performed significantly worse in memory and cognitive speed tests than people who had worked regular hours.
The level of mental decline seen in people who worked irregular shifts for 10 years was equivalent to six and a half years’ worth of natural, age-related cognitive decline, said researchers. The study evaluated participants in 1996, 2001 and 2006. One in five of them had worked shift patterns rotating between mornings, afternoons and nights. Those who were currently or had previously worked shifts had lower scores on memory and processing speed tests than those who worked ordinary office hours.
The research team found that stopping shift work was linked with an improvement in cognitive function – suggesting that any ill effects are reversible – but said that it took five years out of shift work for this effect to be seen.
Publishing their findings online in the journal Occupational and Environmental Medicine on 3 November, the authors, led by Dr Jean-Claude Marquié of the University of Toulouse, concluded: “The cognitive impairment observed in the present study may have important safety consequences not only for the individuals concerned, but also for society as a whole given the increasing number of jobs in high-hazard situations that are performed at night… The current findings highlight the importance of maintaining a medical surveillance of shift workers, especially of those who have remained in shift work for 10 years or more.”