If you run a factory or some sort of output business, you’d understandably want it to run as long as possible — 24/7, if that can be done. In practice, this translates to shift work. Shift work is very common, with 1 in 5 US employees working shifts.

Previous research has linked shift work to a number of health problems starting with insomnia and excessive sleepiness, and escalating to severe issues like increased risk of diabetes and even some types of cancer. Basically, shift work forces people to change their sleeping patterns, which in turn, seems to cause various health problems. Cardiovascular disease, obesity, and substance abuse are also linked with shift work.

But the potential impact of shift work on higher brain functions, such as mental processing speed and working memory, has been less explored. Now, a review of multiple studies found that shift working is also associated with a number of cognitive changes.

The researchers analyzed 18 studies published between 2005 and 2020. In total, 18,802 participants (average age 35) were included.

Five out of the 18 studies compared workers in shift studies to those working normal hours, while 11 compared workers in rotating shifts with those doing normal office hours; two studies didn’t specify the shift type but were included anyway. The studies also included various professions, including healthcare professionals, IT staff, police officers, etc.

Although the literature isn’t comprehensive, when all the results were pooled together, the researchers found that shift work seems to significantly affect working memory, processing speed, impulse control, the ability to filter out unimportant visual cues, and the ability to shift between tasks. In addition, all studies found that workers in shift jobs have worse performance.

The findings are unsurprising — working outside our natural sleep pattern forces our brain to do things it’s not comfortable with. In particular, operating outside the day-night cycle interferes with the expression of cortisol and melatonin, two hormones associated with a number of vital health processes.

If you do work shifts, it’s important to be aware of these issues and monitor any medical conditions. In addition, having a good recovery plan and paying extra attention to getting rest can make a big difference. Researchers also call for more studies on these issues, especially given how many people work shifts around the world.

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

“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.”

The research has been published in BMJ.