It is estimated that nearly one in five people in Europe do shift work – so a lot of people will be worried by research showing a link between it and a reduction in the ability to remember and think clearly. The research, from the Université de Toulouse and Swansea University, assessed 3,232 adults in south-west France on a variety of cognitive tests. The study compared the results of those who had never done shift work with those who had done more than 50 days in a year. They then looked at how long people had done shift work for and how long it had been since they had stopped. They estimated that 10 years of shift work had the effect of ageing the brain by an extra 6.5 years, based on the results of the cognitive tests. They also concluded that it took five years to recover that level of function after stopping shift work. So is the “graveyard shift” really killing our brain cells? Or does this study just suggest an association, rather than prove that shift work damages the brain?

The solution

There is no shortage of research on how shift work is bad for health. But people often don’t have a choice, many healthcare professionals included. The shifts suspected of causing most harm include nights, getting up before 5am, not being able to go to bed before midnight and rotating shifts (alternating morning, afternoon and night shifts). The cognitive tests included being asked to immediately recall a list of words after reading them three times, and matching symbols with numbers as quickly as possible.

There were differences in scores between shift and non-shift workers at the start of the study and these did not change – so it’s hard to say that working patterns caused the differences in cognitive ability and memory. The differences in scores were also quite small.

However, research does suggest that shift work takes it toll – the chief mechanism being the disruption of circadian rhythms and physiological stress. In a review of the evidence, the Institute for Work and Health in Canada found that shift workers are more likely to injure themselves at work and to have mental health and gastrointestinal problems. There is some evidence of an increased risk of breast and colorectal cancer. Shift workers are also more likely to smoke, drink heavily and feel exhausted.

This study couldn’t differentiate exactly which shifts were most troublesome and did not prove that such work damages the brain – but there is more robust evidence that while shift work does suit some people, it can precipitate health problems in others. Some research suggests that limiting night shifts to three in a row and giving employees some control over which shifts they work can help.