New studies in the United States may explain why some people can function on just a few hours of sleep per night. The study examines specific genes and whether or not sleepiness may be genetic.
Researchers discovered, healthy adults carrying DQB1*0602, a sleep gene, were more tired after experiencing multiple nights of poor sleep. This gene has been linked to narcolepsy, a disorder causing people to feel tired throughout the day. However, carrying this gene does not mean a person has narcolepsy. In fact, about 25 percent of those carrying the gene actually have no sleep problems, and those without the gene can develop the disorder.
The study was published in Neurology in the October 26 online edition.
If researchers confirm their findings, recommendations including naps or caffeine intake may be recommended for carriers of this gene, when experience sleep deprivation.
Researchers analyzed healthy adults who did not have sleep disorders in a sleep laboratory. Selected for the study were 37 adults who have the gene, and 92 adults who do not.
All participants spent 10 hours in bed for the first two nights and were completely rested.
For the following five nights, sleep restriction occurred. Participants were allowed only four hours in bed each night. No food or drink known to affect sleep was allowed, such as bananas, turkey, caffeine or alcohol.
During the week, researchers analyzed participants on sleep quality, memory function, and how well they could remain awake and alert throughout the day.
Researchers found carriers of the gene to be less likely to want additional sleep after being completely rested. On the second night of complete rest, carriers averaged less than 35 minutes of stage 3 sleep and non-carriers about 43 minutes.
On the fifth night of sleep restriction, gene carriers received 29 minutes of stage 3 sleep on average, and non-carriers spent 35 minutes.
Also, carriers were more tired and fatigued than non-carriers, and spent less time in deep sleep on sleep restricted nights. However, no evident differences existed between carriers and non-carriers in terms of memory function and attention.