(HealthDay News) – Delaying sleep by just a few hours for several days reduces circadian gene expression in the blood six-fold without affecting centrally-driven melatonin circadian rhythms, according to a study published online Jan. 20 in the Proceedings of the National Academy of Sciences.

Simon N. Archer, PhD, from the University of Surrey in Guildford, UK, and colleagues analyzed changes in gene expression in the blood of 22 healthy volunteers who were placed on a mistimed sleep cycle, where sleep was delayed by four hours for three consecutive days.

The researchers found that mistimed sleep led to a reduction in circadian transcripts in the blood, from 6.4% to 1%, without affecting the centrally-driven circadian rhythm of melatonin. The genes affected included those associated with chromatin modification, transcription, translation, temperature-regulated transcription, and core clock genes.

“The data show that mistimed sleep affects molecular processes at the core of circadian rhythm generation and imply that appropriate timing of sleep contributes significantly to the overall temporal organization of the human transcriptome,” Archer and colleagues conclude.

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