Shift work impacts working memory, impulse control

Shift work has long been linked to health risks due to body clock disruption, but new analysis shows it may even impact higher brain functions, including memory and mental processing speed.

This has implications on workplace health and safety, researchers say, suggesting measures such as naps, recovery plans and regular monitoring to minimise risks and improve outcomes.

Researchers reviewed 18 different studies, published between 2005 and 2020, involving 18,802 participants, looking at the impact of shift work on cognitive performance in working adults. The studies covered six different outcomes measured by formal tests, including processing speed; working memory; alertness (psychomotor vigilance); impulse control and situational response (cognitive control); ability to filter out unimportant visual cues (visual attention); and ability to unconsciously shift between tasks (task switching).

Five of the studies compared workers in fixed shifts with those working normal office hours, while 11 compared workers in rotating shifts with those working normal office hours. Two studies didn’t specify shift type. Half the studies included healthcare professionals while the other half focused on different professions, such as police officers, IT staff, etc.

The pooled data analysis indicated significantly worse performance in shift workers than other types of workers for five of the six outcomes assessed. Shift work was also associated with lower levels of alertness and visual focus, and the ability to control impulses and situational response, potentially heightening the risk of workplace injuries and errors, suggested the researchers.

Working outside the normal day–night cycle interferes with the circadian rhythm and the expression of the hormones that govern it — cortisol and melatonin — which in turn disrupts the sleep–wake cycle, the researchers explained.

Although this is the first pooled data analysis to look at the impact of shift work on different aspects of brain function among working adults, the researchers acknowledge certain limitations to their findings. These include the wide variety of tests used to assess cognitive performance and differing definitions of shift work in the included studies.

Also, because jobs differ in terms of demands and workloads, the results might over- or underestimate the impact of shift work in specific types of profession, the researchers cautioned. And since the included studies were of cross-sectional design, it’s not possible to conclude that shift work does impair higher brain function performance, they added.

Reduced neurobehavioural performance in shift workers might play an important role regarding work-related injuries and errors, with implications for workplace health and safety, the researchers wrote.

“When a more consistent body of high-quality literature is available, we highly recommend replication of analysis to develop practical interventions to overcome neurobehavioural impairment,” they said

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