Mistimed sleep disrupts human molecular clock

A new study, conducted by sleep and systems biology researchers from the University of Surrey, has found that the daily rhythms of many genes are disrupted when sleep times shift.

The research, funded by a grant from the BBSRC and conducted in the University of Surrey's Clinical Research Centre, saw 22 participants placed on a 28-hour day schedule, with their sleep-wake cycle delayed by four hours each day until sleep occurred during the middle of the day. Researchers then collected blood samples to measure the participants' rhythms of gene expression.

Results revealed that during the disruption of sleep timing, there was a six-fold reduction in the number of genes that displayed a circadian rhythm - the clock that regulates the daily cycles of our bodies as we transition from day to night and wakefulness to sleep. This included many regulators associated with transcription and translation, indicating widespread disruption to many biological processes.

The study, published in the journal PNAS (Proceedings of the National Academy of Sciences), also revealed which genes may be regulated by sleep-wake cycles and which are regulated by central body clocks. This finding provides new clues about sleep's function as separate from the circadian clock.

Professor Derk-Jan Dijk, who led the research, says, ''The results suggest that sleep-wake cycles affect molecular mechanisms which are at the core of the generation of circadian rhythms of gene transcription.

''This research may help us to understand the negative health outcomes associated with shift work, jet lag and other conditions in which temporal organisation is compromised.

''The results also imply that sleep-wake schedules can be used to influence bodily processes, which may be very relevant for conditions in which circadian rhythmicity is altered, such as in ageing.''

Dr Simon Archer, one of the leading authors of the research, adds, ''Over 97 per cent of rhythmic genes became arrhythmic with mistimed sleep and this really underlines why we feel so bad during jet lag, or if we have to work irregular shifts.''

This research complements the findings of a Surrey study published last year which revealed that as little as one week of inadequate sleep is enough to alter the activity of hundreds of genes. Read more about this research here.