Researchers placed 22 participants on a 28-hour day in a controlled environment without a natural light-dark cycle.
As a result, their sleep-wake cycle was delayed by four hours each day.
The team then collected blood samples to measure the participants' rhythms of gene expression.
During this disruption of sleep timing, there was a six-fold reduction in the number of genes that displayed a circadian rhythm (internal body clock with 24-hour cycle), said the study published in the journal Proceedings of the National Academy of Sciences.
