Shift work harms cognition

Working anti-social shifts over many years can dent your brain power, a new study has shown... 

Previously, many studies have examined the health impacts of shift work, confirming elevated risks of heart disease, stroke and diabetes in night workers. But no data current exist exploring the short and long-term cognitive impacts of shift work. 

To address this, a team led by Philip Tucker from Swansea University in the UK used data collected by the French National Institute for Statistics and Economic Studies on more than 3000 workers. These people, who were aged between 32 and 62, underwent tests of brain function ten years apart; memory, mental reasoning and attention tasks were probed. 

The data showed that individuals who had worked night shifts for over 10 years had the same conitive test scores as someone up to six and a half years older than them. The team speculate, in their paper in Occupational and Environmental Medicine, that the results reflect the effects of "circadian stress" caused by defying the body clock. This stress in turn can damage the hippocampus, a brain structure concerned with learning and memory. However, more cheerily, the effect does appear reversible. 

Individuals with the same shift work history but who had ceased this working pattern more than 5 years previously showed that their cognition had returned to what would be expected based on their age.

According to the researchers, this recovery might reflect the fact that the hippocampus is one of a small number of sites in the brain capable of producing new nerve cells. These, the team say, might be patching up the damage done by former shift-work, leading to a recovery of cognitive function. 

But can anything be done to prevent the damage in the first place?

"Switching to a day-shift would be the best way to prevent it," counsels Tucker, "but that's not always possible. Under those circumstances, limiting the number of nights worked in one go to fewer than three is a sensible option. This stops the body clock becoming completely upset..."