Working shifts may worsen memory, reduce mental processing speed

Working shifts rather than a nine-to-five job blunts people’s brain, warns a new study. Scientists say employees who clock in and out are more likely to have a weaker memory, and struggle to keep a sharp and focused mind. It could lead them to make mistakes and potentially hurt themselves.

Shift work has been linked to a wide range of health problems including heart and blood disease, obesity, diabetes, sleep and mood disorders, as well as substance abuse. This is because it messes with circadian rhythm, which helps govern many of the body’s biological processes.

But its impact on brain functions like processing and remembering information have remained a mystery. Now scientists say people working shifts could be putting themselves and others at risk.

“Reduced neurobehavioral performance in shift workers might play an important role regarding work-related injuries and errors, with implications for workplace health and safety,” the authors write.

A 2019 study estimates that anywhere from 26 to 38 million Americans are shift workers — or about 18% to 26%.

Data from 18 studies, published between 2005 and 2020, involving 18,802 participants was analyzed by the researchers. The studies compared workers in fixed and rotating shifts with those pulling normal office hours, although two did not specify what type of work.

Half of the studies looked at healthcare professionals, while the others focused on different professions like police officers or IT workers. In total, the studies measured six different criteria including the workers’ mental processing speed and their ability remember information. They also looked at their level of alertness and cognitive control, as well as their ability to filter out unimportant visual cues and shift between tasks.

Shift workers performed worse on five of the six outcomes, the researchers report. Especially in terms of cognitive control, a person’s ability to select information and change their behavior accordingly, shift workers lagged behind.

Only when it came to changing between tasks did shift workers step up to the plate.

Researchers say companies should therefore take steps to protect shift workers from the strains of their job, like allowing for naps and recovery time.

“Protective countermeasures for reduction in neurobehavioral performance of shift workers should be promoted to minimize the risk of adverse health and work-related outcomes,” they write.

The selected studies used different definitions of shift work and a wide range of tests to assess the workers’ cognitive abilities, the researchers warn.

“When a more consistent body of high-quality literature is available, we highly recommend replication of analysis to develop practical interventions to overcome neurobehavioral impairment,” the study concludes.

The findings are published in the BMJ.

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Steve Fink

Steve Fink is the Editor-in-Chief of, and He is formerly the Vice President of News Engagement for CBS Television Stations’ websites, and spent 20 years with CBS.

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