MONDAY, Oct. 25 (HealthDay News) -- Why is it that two people
can be equally sleep-deprived, and yet the next day one person ends
up feeling more tired and listless than the other?
The answer could be in their genes, a new study suggests.
Researchers at the University of Pennsylvania School of Medicine
found that healthy individuals who test positive for a common gene
variant are sleepier and more fatigued after being sleep-deprived
than people who don't. The variant is related to narcolepsy, which
causes excess daytime sleepiness, but previous studies have shown
that up to one-third of people who test positive for the gene are
considered normal, healthy sleepers.
"This particular gene, which is carried by roughly 30 percent of the population, may be a biomarker for predicting how someone will respond to getting too little sleep," said study author Namni Goel, an assistant professor of psychology and psychiatry at the University of Pennsylvania School of Medicine in Philadelphia.
"This study provides hard evidence that genes can play a key role in determining how we respond to sleep deprivation," said Dr. Jeffrey Ellenbogen, chief of sleep medicine at Massachusetts General Hospital. "Keep in mind that the kind of sleep deprivation examined in this study, so-called 'partial sleep deprivation,' is not just a lab technique, it's something that happens to millions of people, for a variety of reasons," he added. "And this genetic marker is common. So we're talking about a lot of people that this study potentially describes."
For the study, which was published in the Oct. 26 issue of
Neurology, Goel and her colleagues studied 92 healthy adults without the gene variant and 37 healthy adults who had the gene variant but did not have any sleep disorders. For the first two nights, they spent 10 hours in bed and were fully rested. The next five nights they underwent chronic partial sleep deprivation, where they were allowed four hours in bed per night. During the remaining time, lights were kept on and participants could read, play games or watch movies to help them stay awake.
During the study, the researchers measured the participants'
sleep quality and self-rated sleepiness, and also tested their
memory, attention and ability to resist sleep during the daytime.
The people with the gene variant were sleepier and more fatigued
whether they were fully rested or sleep-deprived, and their sleep
was more fragmented. For example, during the fifth night of sleep
deprivation, those with the gene variant woke up, on average,
almost four times, while those without the variant woke up, on
The people with the gene variant had a lower desire to sleep
during the fully rested nights. And they also spent less time in
deep sleep than those without the variant, during both the fully
rested and sleep-deprived nights, the investigators found.
There was no difference in how the two groups performed on tests
of memory and attention after being sleep-deprived, and there was
also no difference in their ability to resist sleep during the
daytime. One possible explanation for these particular findings is
that "there might be different genetic variants that regulate
physiological responses to sleep deprivation versus how people are
able to perform," Goel said.
"Sometimes, people rate themselves as feeling fine and yet their performance is terrible, or vice versa," Goel explained. She added that more studies are needed to replicate these findings in other populations, as well as to identify other possible biomarkers that can explain why some people seem to be particularly resistant to the ravages of sleep deprivation.
The authors of an editorial accompanying the study said the
findings "are particularly important in individuals involved in
shift work and transcontinental travel," and noted that they hoped
the research would lead to new treatments to minimize or eliminate
the effects in people who respond poorly to sleep deprivation.
"There's always a tendency for people to make judgments about someone who sleeps until noon, and say they're lazy or something," said editorial co-author Dr. Amit Verma, medical director of The Methodist Hospital's Sleep Disorders Center in Houston. "But what this study highlights is that if you're sleepier than your friend or your spouse after being sleep-deprived, there may actually be a genetic reason."
For more on sleep disorders, visit the
U.S. National Library of Medicine.