Popular strategy for adjusting to “vampire hours” throw off human circadian clocks

Going without sleep for at least 24 hours in order to adjust to night-time schedules is the least effective of five distinct strategies humans use to adjust their circadian clocks. Yet it is a strategy employed by 25 percent of more of those participating in the first study of strategies used to adjust between day and night sleep cycles.  The most common strategy, used by about half of the participants was to sleep in late on the morning prior to their first night shift. The least popular method was to maintain a night schedule at all times.

It’s not often that you identify and characterize a human behavior for the first time, let alone on that has an effect on human health, ” stated Chris Ciarleglio, a graduate student at Vanderbilt University and co-author of the study.

In addition to examining the strategies used, the researchers also took DNA samples to investigate the extent of the influence each participant’s circadian clock had on their adaptation. Results indicate that variations in the circadian clock genes have a discernible impact on adaptation to and from the night shift. This finding raises concerns and requires additional investigation because previous studies have shown that repeated incidence to circadian misalignment has been associated with increased risk of developing cardiovascular, metabolic and gastrointestinal disorders as well as some type of cancer and several mental disorders. In other words, continuously switching his sleep cycles may have made Renfield ever crazier than blood loss and Dracula’s brainwashing.

Using the DNA samples, researchers were able to determine each participant’s “chronotype” as well as which of the seven well-known variations or polymorphisms in the human circadian clock each possessed. This information allowed researchers to determine that larks, those who are naturally early risers,  adapt particularly well to day shifts and poorly to night shifts. Owls, or those who are naturally late risers, do not adapt particularly well or poorly to either the day or the night shift.

Further, researchers found that variants in one gene, called PER3, appears to have a major impact n the effectiveness of the no sleep strategy. Individuals with one variant of this genotype appear to respond more poorly than average to the strategy while those with the other genotype appear to respond better than average.

The results of the study were published in the 13 April, 2011 issue of the scientific journal, Public Library of Science One.

Five Sleep Strategies
Strategies for adapting to "vampire hours"

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