Are You an Owl or a Lark?

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Author:

Christine Haran

Medical Reviewer:

Qanta Ahmed, MD

Medically Reviewed On: March 29, 2004

Do you find that you?re most alert after everyone else has turned in for the night? Or are you the type to hit the deserted streets for a run at 5:30 a.m.? While all humans are essentially programmed to sleep at night and be active during the day, some people have a marked morning or evening preference.

"There?s really a spectrum from morningness to eveningness," says Dr. Jamie Zeitzer, a fellow in the Sleep Research Center at Stanford University in California. "Most people fall in the middle, but there are people who are on each extreme."

Researchers believe that owls?a term for people who like to stay up late?and larks?people who like to get up early?have their body clocks set to different schedules. The body clock, also described as the body?s circadian rhythm, controls sleep-wake patterns by regulating body temperature and hormones such as melatonin and cortisol.

"In most people, melatonin rises just before you go to bed and drops just after you wake up," Zeitzer says. "The stress hormone cortisol peaks just before you wake up, and the body temperature hits the lowest point around the middle of a night?s sleep." In larks, for example, these hormonal fluctuations and temperature rhythms occur earlier than they do for most people, so they get tired earlier in the evening and perform best in the morning.

Although many sleep researchers believe there is a genetic basis for a morning or evening preference, an associated genetic mutation has not yet been found. Zeitzer points out that social factors, as well as biology, can influence one?s preference. For example, college students are often temporary owls, staying up until 3 or 4 a.m. because of academic and social pressures. Other people may become lark-like because they have a two-hour commute to work. While most people can revert back to regular schedules it can be a difficult habit to break.


People who are owls, but have to function on a "normal" schedule can end up sleep deprived due to insomnia. Larks tend to have fewer problems due to their sleep habits, though their social lives may suffer. And larks who have to work at night, such as medical residents and other shift workers, find that they tire out much earlier than their peers.

Still, most owls and larks can reset their body clocks although it might take a bit of doing. Zeitzer suggests that owls begin gradually going to bed earlier. "You may say ?Well, I?ll try to go to sleep at midnight. I won?t get eight hours of sleep, but I?ll just try to get six.?" He also advises that owls sleep in a dark, quiet and temperate room. Likewise, he recommends that larks who have to be up late at night minimize their light exposure in the morning and create good sleep conditions.

"The most potent thing to affect circadian rhythms by far is light," says Zeitzer, who adds that exercise in the morning may help owls stay awake and that taking a melatonin supplement before going to sleep in the morning may assist larks who work at night.

People with an extreme sleep preference, however, are classified as having a sleep disorder: Extreme morningness is referred to as advanced sleep phase syndrome (ASPS) and extreme eveningness is called delayed sleep phase syndrome (DSPS). "While being a ?lark? or an ?owl? will change your social, work or life structure to a degree, having ASPS or DSPS can have a significant impact on your ability to have normal interactions with society," Zeitzer says.

Older people sometimes develop ASPS, possibly because they tend to nap during the day and are less able to filter out sensory information such as light and noise. In certain cases, people with ASPS or DSPS may require light therapy or medication to help them get the sleep they need.

Most owls and larks, though, are able to work within society?s schedule. Friends and family just need to remember that calls to a lark after 10 p.m., or to an owl before 10 a.m., might not be welcome.