Sleep During the Day May Throw Genes Into Disarray01/21/14
TUESDAY, Jan. 21, 2014 (HealthDay News) -- Sleeping during the
day -- a necessity for jet-lagged travelers and those who work
overnight shifts -- disrupts the rhythms of about one-third of your
genes, a new study suggests.
What's more, shifted sleep appears to disrupt gene activity even
more than not getting enough sleep, according to the research.
For the new study, which was published in this week's issue of
Proceedings of the National Academy of Sciences, British
researchers put 22 healthy, young volunteers in a dimly lit sleep
lab for three days.
During the first day, they disrupted the participants' sleep at
regular intervals to reset their body clock to its innate rhythm.
On the second and third days, the volunteers ate and slept on a
28-hour schedule, so their longest period of sleep was from noon
until about 6:30 p.m.
The researchers drew blood samples all three days so they could
watch what happened to the timing of gene activity.
During the first day, when the body reset its circadian rhythm,
nearly 1,400 genes -- about 6.4 percent of all genes that were
analyzed -- were in sync with that rhythm. On the days of shifted
sleep, however, the number of genes tied to the body's clock
dropped dramatically, to 228 genes, or only 1 percent of genes
The researchers estimated that the sleep disruptions would
ultimately impact about a third of a person's genes.
That's an even greater disruption than scientists saw in a
previous study when they tested the effects of sleep deprivation on
gene activity. In that study, which had study volunteers sleeping
about five and half hours each night, the number of genes that were
in sync with the body's clock dropped from about 9 percent to 7
"These are quite fundamental processes that are being affected," said senior study author Derk-Jan Dijk, a professor of sleep and physiology at the University of Surrey, in the United Kingdom.
"We think that may be related to the negative health outcomes associated with long-term shift work," Dijk said. Shift workers are at higher risk for many health problems, including obesity, diabetes, high blood pressure, heart disease, disrupted menstrual cycles and cancer, he said.
This study didn't directly connect health problems and
night-shift work, but experts said it does start to help them
understand why sleep might have such a powerful influence on a
"This study suggests that mistimed sleep can alter circadian rhythms, so the cycling of many, many genes is impaired," said Dr. Mark Wu, assistant professor of neurology, medicine, genetic medicine and neuroscience at Johns Hopkins University. "What this could cause, they can't really say -- except it's probably not good." Wu was not involved in the new research.
Genes carry the instructions for making proteins. Proteins make
up just about every kind of chemical signal, hormone and tissue in
the body, the researchers said.
The timing of when proteins are made is important because their
production should correspond to our behaviors, said Frank Scheer, a
neuroscientist at Harvard and director of the Medical Chronobiology
Program at Brigham and Women's Hospital in Boston.
When the body anticipates a meal, for example, the liver has to
stop releasing into the blood the carbohydrates it has stored and
the pancreas has to make more insulin, while the muscles have to
become more sensitive to insulin that's released so they can take
in blood sugar, Scheer said.
"If these processes are working in concert and they're synchronized to when you eat and when you fast, then the system is very efficient and effective at absorbing these sugars quickly and minimizing any adverse consequences of elevated blood sugar levels," Scheer said.
"If these are not rhythmic, then you can easily imagine that, during the nighttime, you have this machinery up and running without need," he said. "During the daytime, when you actually do need it, it's only running half speed."
U.S. Centers for Disease Control and
Preventionfor more on sleep.
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