In addition, alertness, visual attention, impulse control, and situational responsiveness are all reduced. This could also increase the likelihood of occupational injuries and mishaps.

A pooled data analysis of the available evidence published online in Occupational & Environmental Medicine indicates that shift employment is connected to poorer working memory and slower mental processing speed.

It’s also linked to decreased levels of attentiveness and visual focus, as well as the ability to manage impulses and situational response, suggesting that it could increase the likelihood of job injuries and errors.

If your internal body clock (circadian rhythm) isn’t in sync with the normal light-dark cycle, shift work can be dangerous. Among the most common are issues with sleep disorders, heart disease, weight gain, type 2 diabetes, depression, and substance abuse.

There’s still a lot we don’t know about how it might affect things like mental processing speed and working memory.

In order to clear up these doubts, the researchers combed through research databases seeking studies on the influence of shift work on working adults’ cognitive ability.

In total, 18 studies were selected, with 18,802 individuals (average age 35) and six different outcomes determined by formal tests, published between 2005 and 2020.

This study looked at the following: processing speed and working memory; alertness (psychomotor vigilance); impulse control and situational response (cognitive control); the ability to filter out unimportant visual cues (visual attention); and the ability to switch between tasks without thinking about it (task switching).

Five of the studies compared workers who worked fixed shifts to those who worked regular office hours, whereas 11 compared workers who worked rotating shifts to those who worked regular office hours. The shift-type was not specified in two of the studies.

Half of the research involved healthcare workers, while the other half focused on a variety of other occupations, such as police officers and information technology experts.

When the results of the studies were combined, they revealed that shift workers performed significantly worse than other types of workers in five of the six outcomes studied.

Impulse control and situational reaction had a substantial and significant effect, but processing speed, working memory, alertness, and the ability to filter out irrelevant visual signals had a minor but significant influence. Task switching had no effect.

Working outside the regular day-night cycle affects the circadian rhythm and the expression of the hormones that regulate it–cortisol and melatonin–destabilizing the sleep-wake cycle, the researchers say.

Although this is the first study to look at the influence of shift work on many areas of brain function in working people using pooled data, the researchers recognize that their findings have certain limitations.

These include a wide range of cognitive tests and different definitions of shift work in the studies that were included.

They warn that because jobs differ in terms of demands and workloads, the findings may exaggerate or underestimate the impact of shift work in individual professions. They also point out that because the research included were of a cross-sectional design, it’s impossible to establish that shift work affects higher brain function performance.

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

They conclude: “Protective countermeasures (eg: naps, recovery plans, regular monitoring) for reduction in neurobehavioural performance of shift workers should be promoted to minimise the risk of adverse health and work-related outcomes. 

“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.”

Source: 10.1136/oemed-2021-107847

Image Credit: Getty

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