Technicians work on a Toyota Corolla assembly line, Blue Springs, Mississippi, Feb. 12, 2015.
Technicians work on a Toyota Corolla assembly line, Blue Springs, Mississippi, Feb. 12, 2015.

People who walk around in a seemingly inexplicable fog of grogginess may suffer from “social jet lag,” and the solution could be an adjustment in their work schedules.

That's what a team of researchers at Ludwig-Maximilian University in Munich, Germany, are reporting in a study of workers at ThyssenKrupp Steel Europe. 

Researchers coined the term to describe that foggy feeling — that sense of being out of it — which affects many people. 

The problem, says biologist Till Roenneberg, who led the research, is that many people are working on schedules that don’t match their body’s natural sleep-wake cycle, called the circadian rhythm.

“... Meaning your body clock would give you the optimal window for sleeping — let’s say between midnight and eight o’clock [in the morning] or even later — but your social schedules would like you to fall asleep at ten o’clock and get up at six o’clock with the work times, for example," he said. "That discrepancy is very much like a jet lag situation.”

With jet lag, people feel extremely tired when they travel from one time zone to another, ending up in a place where the sleep-wake cycle is different from what their bodies are used to.

In the Roenneberg-led study, factory workers were assigned early or late shifts to match their natural sleep tendencies. So-called “night owls” were never forced to get up early for work, while "early risers" were not made to work late.

Roenneberg says the adapted schedules improved the workers’ sense of well-being.

“They sleep up to almost an hour longer on work days and therefore much shorter on their free days," he said. "Normally, people have to catch up on their sleep loss on their work-free days. And we have shortened sleep on work-free days and lengthened sleep on work days.”

In other words, with the extra hour of sleep, workers reported feeling more rested as well as finding slight improvements in their general wellbeing.

However, the study also found that night owls did not report the same level of benefit, suggesting that nighttime shift work is hard on everyone.

Roenneberg says employees who wake more refreshed are more productive.

“We still have to convince the employers that this is of financial benefits for them; and of course the workers, too, that it is [has] health benefits for them," he said. "And so this just the beginning and that’s why we went into a large industry to do this experiment to show that it works.”

Roenneberg’s team now plans to investigate a suspected link between “social jetlag” and health problems, including obesity, in experiments with mice.

Their latest study was published in the journal Current Biology.