Night Shifts Disrupt Genes' Daily Rhythms

Reversing one's sleep cycle disrupts genes' daily rhythms, a new study published in the journal Proceedings of the National Academy of Sciences found.

The researchers, from the University of Surrey, ran an experiment in which they placed 22 people on a 28-hour day in a controlled environment that lacked a natural light-dark cycle. The result was a four-hour delay in the participants' sleep-wake cycle every day.

This continued until the participants were sleeping in what would normally have been the middle of the day.

Blood samples taken during this period revealed a six-fold reduction in the number of the participants' genes displaying a circadian rhythm, the roughly 24-hour internal cycle often referred to as the "body clock."

Among those affected were regulators involved in transcription, or the process in which an RNA copy of a gene sequence is created, and translation, involved in protein synthesis.

"Over 97 percent of rhythmic genes become out of sync with mistimed sleep and this really explains why we feel so bad during jet lag, or if we have to work irregular shifts," said co-author Dr. Simon Archer, from the School of Biosciences and Medicine at the University of Surrey.

By identifying those genes that may be regulated by the sleep-wake cycle and those regulated by central body clocks, the study offers insights into sleep's function separate from the circadian clock, the scientists said.

"This research may help us to understand the negative health outcomes associated with shift work, jet lag and other conditions in which the rhythms of our genes are disrupted," said senior author Derk-Jan Dijk, from the Sleep Research Center at the University of Surrey.

"The results also imply that sleep-wake schedules can be used to influence rhythmicity in many biological processes, which may be very relevant for conditions in which our body clocks are altered, such as in [aging]."