After a night of only a few hours of sleep, some people seem to cruise through the next day unaffected, while others struggle all day long to hold their bleary eyes open. Now, scientists have identified a gene that may help explain why.
The gene, known as DQB1*0602, is found in most people with narcolepsy, a condition in which individuals are excessively sleepy during the day. About 12 percent to 38 percent of those with the gene do not have narcolepsy, and are thought to have healthy sleep patterns.
The hew study showed when "healthy sleepers" who have the DQB1*0602 gene were deprived of sleep , they felt more sleepy and fatigued than those without the gene. They also experienced changes in their sleep patterns that, in a sense, made them behave more like people who have narcolepsy.
"These are normal healthy people who respond a lot like narcoleptics do," to sleep deprivation, said study researcher Namni Goel of the University of the Pennsylvania School of Medicine in Philadelphia.
However, sleep deprivation worsened performance during attention and memory tests in those with and without the gene.
One day researchers might be able to use this gene, and others that have been identified, to predict how individuals will respond to a lack of shut-eye, Goel said. This information might be important to those who work night shifts, travel often or frequently lose sleep, she said. However, more research is needed to confirm the findings.
The study involved 92 adults without the DQB1*0602 gene, and 37 "healthy sleepers" with the gene. For their first two nights in a sleep laboratory, participants got a full 10 hours of sleep per night. During the next five nights, their sleep was restricted to just four hours each night.
Even without sleep deprivation, those with the DQB1*0602 gene had some differences. They reported being more sleepy and fatigued when they were fully rested than those without the gene. After sleep restriction, this sleepiness and fatigue got even worse.
And on the nights of limited sleep, those with the gene had more fragmented sleep. For instance, on the final night of sleep restriction, those with the gene woke up four times on average, while those without the gene woke up twice.
Those with the gene also entered the REM stage of sleep faster during sleep deprivation, a response that is characteristic of people with narcolepsy.
The researchers hope future work will reveal more genes involved in the response to sleep loss, Goel said.
The study will be published Oct. 26 in the journal Neurology.