Do you toss and turn in bed, awaking every few hours, while your partner slumbers soundly and peacefully?
Do you find it impossible to go to sleep before midnight while others you know stumble off to bed and fall deep into dreamland at 10 p.m.?
There may be a biological reason for all this.
In two studies released this week, researchers say they have discovered variations in genes that may explain why some people have trouble sleeping and other people are so-called “night owls.”
Still, the researchers say, a lot of questions remain unanswered.
Discovery of the “sleep gene”
The first study was published Wednesday in the journal Science Advances.
In it, researchers focused on genes that change expression in the sleep-wake cycle.
The researchers studied mice and discovered the expression of the gene FABP7 changed during the day in the brains of small rodents.
They noticed mice with a “knocked out” FABP7 gene slept more fitfully. The researchers concluded that particular gene is necessary for normal sleep in mammals.
The researchers also checked the FABP7 gene in humans.
They combed through the data from nearly 300 Japanese men who participated in a sleep study that included DNA analysis.
In 29 of the men, the FABP7 gene did not appear to function properly and those men slept fitfully. The researchers said the men got as much sleep as other participants, but they experienced more waking moments and they didn’t sleep as soundly.
Finally, the researchers made transgenic fruit flies, inserting mutated and normal human FABP7 genes into the insects.
Researchers said they noticed fitful sleep in the flies that had the mutated gene.
“Sleep must be serving some important function,” Jason Gerstner, PhD, research assistant professor at Washington State University's College of Medicine, and lead author of the paper, said in a press release. “But as scientists we still don't understand what that is. One way to get closer to that is by understanding how it is regulated or what processes exist that are shared across species.”
Gerstner said other genes are almost certainly involved in the sleep process. He and his team hope to find those biological links, too.
Why people are “night owls”
The second study was published today in the journal Cell.
In it, researchers say they have discovered a variant in the gene CRY1 that slows a person’s biological clock.
This so-called “circadian clock” dictates when a person feels sleepy each night and when it’s time to wake up.
People with the “night owl variant” have a longer circadian cycle, causing them to stay awake later, the researchers said.
For their study, Michael W. Young, PhD, head of The Rockefeller University Laboratory of Genetics, and research associate Alina Patke, collaborated with sleep researchers at Weill Cornell Medical College.
They observed volunteer participants for two weeks in a laboratory apartment that was isolated from any clues as to what time of day it was. Participants were allowed to eat and sleep whenever they wanted.
Young said most people followed a typical 24-hour sleep/wake cycle. However, one person with delayed sleep phase disorder (DSPD) did not follow this pattern.
Among other things, the researchers noticed this person’s release of melatonin was delayed. That chemical helps bring on sleep.
“Melatonin levels start to rise around 9 or 10 at night in most people,” Young said in a press release. “In this DSPD patient that doesn't happen until 2 or 3 in the morning.”
When researchers checked the DNA of the DSPD participant, they said the mutation in the CRY1 gene stood out.
They said this gene mutation made the CRY1 protein more active, keeping other clock genes switched off for a longer period of time.
“This is a fairly impactful genetic change,” said Young.
No small matter
The researchers said sleep abnormalities are nothing to shrug off.
Someone with a “night owl” variant can go to bed later but needs to get up before their body is ready to return to waking status.
The Centers for Disease Control and Prevention (CDC) estimates that at least 50 million Americans have a sleep disorder.
They characterize insufficient sleep as a public health problem.
Young and his team plan further research. Part of that endeavor will be looking for solutions.
“Just finding the cause doesn't immediately fix the problem,” Patke said in a press release. “But it's not inconceivable that one might develop drugs in the future based on this mechanism.”
For now, people with sleep disorders can help ease the problem by adhering to strict schedules.
Young added they can also get strong light exposure during the day.