The results are in from a large four-day work week trial in the UK, and the responses from employees who participated highlight several reasons why it could be a preferable alternative to the status quo – including better sleep.

40 percent of the around 2,900 employees who participated in the trial said they had fewer sleep issues or insomnia, according to the trial's findings. Forty-five percent saw no change in their sleep, and 15 percent reported an increase in sleep issues.

The UK's four-day work week trial, one of the largest in the world, saw 61 companies participate in the trial. A total of 56, or 92 percent of the companies, said they will continue with a four-day work week now that the trial is over. Eighteen of the companies confirmed that the four-day work week is going to be a permanent policy.

The trial was organized by 4 Day Week Global in collaboration with research teams at Boston College, University of Cambridge, and Autonomy. It went from June to December last year.

It's no secret that sleep is important for health, but over a third of American adults don't get the recommended 7 hours or more of sleep each night, according to a 2016 report from the Centers for Disease Control. Being overworked probably isn't the only reason, but the CDC suspects that plays a role.

"Employers can consider adjusting work schedules to allow their workers time to get enough sleep," the agency wrote when it released the report.

Much of the US government's work-sleep research focuses on the long overnight shifts that are often required of nurses or truck drivers. But even with a standard 40-hour work week, stress on the job can bleed into bedtime.

A 2007 study in Sweden linked insomnia to work stressors like high work demands. Further Swedish research in 2019 strengthened that link using health-survey data from over 3,700 people. A meta-analysis by State Farm Insurance in 2017 found that job stressors such as workload impacted both sleep quality and quantity. The US National Institute for Occupational Safety and Health lists sleep disturbances as an early warning sign of job stress.

Poor sleep is a health risk for workers. But it can also affect employers by diminishing job performance. A 2010 study estimated that fatigue-related productivity loss cost $1,967 per employee annually, at four US corporations. A study in 2007 showed that almost 38 percent of employees in the US experienced fatigue at work.

In the 4-day work week pilot, 46 percent of employees reported experiencing less fatigue than usual, and 14 percent said they experienced more.

4-day work weeks are good for business too, study suggests

The companies who participated also said they saw benefits, with revenue increasing by 1.4 percent on average during the trial. Compared to a similar amount of time during a normal five-day work week in the past, participating companies saw revenue increase on average by 35 percent, according to the trial results.

The marketing and advertising industry made up the largest sector of companies that participated in the study, with professional services making up the second largest group, and charities and nonprofits being the third largest. Sixty-two percent of employees in the trial self-identified as women, 37 percent identified as men, and 1 percent identified in the "other" category.

Fewer employees said they felt compelled to leave their jobs during the trial, with the number of employee departures dropping by 57 percent, according to the results. Fifteen percent of employees who participated in the trial "said that no amount of money would induce them to accept a five-day schedule over the four-day week," per the findings.

The results of the survey are telling of the current mood in the workplace, not just in the UK, but also in the US and around the world. Four in ten employees said they dealt with burnout in the last year, according to a survey from the Adecco Group.

In addition to better sleep, participating employees reported other benefits of working 32 hours instead of 40 for the same amount of pay. Thirty-nine percent of employees reported feeling less stress, and 71 percent felt less burnout by the end of the trial.

This article was originally published by Business Insider.

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