Social Jetlag Improved by Altered Work SchedulesMost people are tired after work, but work is especially exhausting for people whose natural body rhythms do not match their work schedule. Working out of sync with one’s internal sleep preferences, called ‘social jetlag’, is measurable and, reports a new study, its effects can be reduced by flexible work schedules. The researchers tested their theory with workers in a factory. They found that matching a worker’s schedule to his or her preferred sleep type improved sleep quantity and well-being.

An initiative to lower stress and improve the health of the employees allowed the researchers to try a flexible working model in a real-world factory. They began by categorizing the workers by their chronotype, a term describing when a person’s natural rhythms would make her want to sleep. The three chronotypes—early, late, or intermediate—were organized into new work schedules. The early chronotype group, which consisted of morning people, was not made to work late. The late chronotype group, which consisted of night owls, was not made to work early. The intermediate group served as the study’s control.

Throughout the study, the researchers monitored the workers’ sleep duration and quality, social jetlag, well-being, subjective stress perception, and satisfaction with leisure time.

Schedules adjusted to a worker’s chronotype resulted in improvements in general well-being, less social jetlag, and greater satisfaction with sleep. Social jetlag, measured as the difference between the midpoint of an individual’s sleep on workday nights versus on free days, was reduced by one hour. Workers with a late chronotype did not have improvements as large as those in the early group, which suggests that night work is challenging for everyone.

“A ‘simple’ re-organization of shifts according to chronotype allowed workers to sleep more on workday nights. As a consequence, they were also able to sleep less on their free days due to a decreased need for compensating an accumulating sleep loss. This is a double-win situation,” stated Till Roenneberg of Ludwig-Maximilian-University in Germany.

The findings suggest that flexible schedules are not just a matter of convenience, but have real health implications for workers. The researchers state that they hope their study will encourage changes in work culture and in how people manage their time.

This research is published in the journal Current Biology.

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