When the alarm goes off at 6:30 a.m., are you the type of person who leaps to their feet, goes for a brisk run and then whistles in the shower? Or do you wince, flip over in bed and pull the sheets over your head, hoping for a few extra minutes of shut-eye?
Whether you're a morning person or a night person depends on your genes, new research suggests. That means that despite your best efforts to rise and shine — or stay up to watch that late movie — your genetic makeup may be working against you.
It also means that when daylight time kicks in, it can be a painful adjustment for people — regardless of which category they fall into. That's because the body's internal clock, the circadian rhythm, is disrupted.
Circadian rhythm
Sleep is regulated by two mechanisms: circadian and homeostatic. Circadian regulation affects the timing of sleep, while the homeostatic mechanism affects a person's need for sleep.Circadian rhythm can be changed during periods of daylight time. However, it is only able to change slowly.
When German researchers examined people during daylight time in both the fall and spring, they found that moving a wakeup time by an hour forward or back had significant effects.
"When we implement small changes into a biological system which by themselves seem trivial, their effects, when viewed in a broader context, may have a much larger impact than we had thought," said Till Roenneberg of Ludwig-Maximilian-University in Munich, Germany, an author of the 2007 study, in a release.
"Our results show that the human circadian clock does not adjust to the daylight saving time transition," Roenneberg said, adding that this is most pronounced in the spring.
Sleep gene found
The idea that someone can change his or her morning or night person status is pretty widespread. People who couldn't get up in the morning are often seen as lazy, while those who go to bed "with the chickens" are seen as boring — the types who can never last during a night on the town.In 2001, however, that thinking was turned upside down — at least scientifically. That year, researchers at the University of Utah zeroed in on a sleep gene called hPer2, found only in people who chose to go to bed at 7 p.m. and slept until 4 a.m. It was a finding that brought to light the fact that genes are responsible for a person's sleep preferences, rather than conditioning or adaptation to one's environment.
The genetic links kept coming. In 2003, British scientists identified a gene called Period 3 which is involved in regulating a person's internal clock. In early-morning types, the gene is longer in length, while in people who prefer to stay up late, the gene is shorter. Then in 2009, the same Utah research group that found the hPer2 gene discovered the first circadian rhythm sleep gene implicated in short sleep, called DEC2-in "short" sleepers. People possessing this gene require only six to 6.6 hours of sleep per night.
Recent research out of the Center for Narcolepsy at Stanford University suggests narcolepsy — a chronic sleep disorder that causes sufferers to be extremely tired during waking hours and often fall asleep instantaneously at inopportune times — is caused by the lack of two brain-related chemicals called hypocretin-1 and -2.
The cells that create those chemicals are missing in the brains of narcoleptic patients. The most likely explanation may be that those cells are destroyed in some sort of auto-immune attack, the school suggests, but more research is needed. Most people with narcolepsy have a gene called HLA-DQB1*0602. It's unclear whether it's a causal relationship or whether it may one day lead to treatment, but still an encouraging sign for the one in 2,000 people who suffer from narcolepsy.