I used to work with one of my roommates and getting up in the morning and heading to our job proved to be one of the most trying times in our friendship. I was up with the alarm clock and onto my morning routine, whereas she would stay in bed well past the ringing. Convinced we would be late, I’d go in and give her some gentle nudging, which never went over well. She’d grumble and complain; sometimes she’d hurl insults like “Leave me alone,” or “I hate you,” or simply, “Die.” Offended, I’d sulk away, even more convinced of our impending tardiness. Later on, over a strong cup of coffee, she’d apologize and we’d have a good laugh, only for the same routine to be repeated the following morning.
Get Up by Your Own CLOCK
As it turns out, our sleeping preferences weren’t just due to the fact that I responded better to the alarm. The circadian rhythm, a 24.1-hour period that dictates the sleep-wake cycle, differs among people and can influence whether we are a night owl or a morning lark.
Studies have indicated that self-described morning people have shorter circadian rhythms than self-identified night owls. This means that morning people sleep through their peak hour of sleepiness, so they wake up feeling refreshed. Evening types usually wake up right around their peak hour of sleepiness, so they may have high levels of melatonin and feel groggy. No wonder it’s tough to rouse them.
Hormones and body temperature also differ between the sleep groups. Early birds have higher levels of cortisol in the morning, which may give them the perky edge. Body temperature tends to be low in the morning, peaks in the late afternoon, and decreases until bedtime. Early risers have a body temperature peak around 3:30 p.m., while night owls are hottest around 8 p.m.
Our sleep preferences are at least in part hereditary. Differences in the CLOCK gene (short for Circadian Locomotor Output Cycles Kaput), for instance, may contribute to differences in our favored times of activity. Sleep researchers at Stanford University found that people with one genotype had an increased preference for eveningness, while the other genotype had an increased preference for morningness.
Biology and Behavior
Though our sleeping and waking preferences may be partially innate, some are due to what we’re used to from childhood, the seasons, or what we’ve adapted to. This means we can—and do—change our sleeping patterns.
For instance, during the summer, when daylight hours are plenty, we may stay up later but rise earlier with the sun. In the winter, darkness and cold sets in early, making our beds all that much more alluring. It’s also harder to wake early in the winter when it’s dark out.
Age also alters our sleeping patterns. Different times in our lives lend themselves to different sleeping patterns. During the teens, for instance, hormones may change the sleep and wake patterns, and this is one explanation as to why so many teens tend to shift to a night owl schedule. (Socializing, studying, and busy schedules also contribute.) Alternatively, as people get older, work and familial demands tend to make people more morning focused, regardless of their preferences. Later in life, in the sixties and seventies, people tend to need less sleep altogether.
In Sleep as in Life?
In reality, however, few of us are true morning people who can effortlessly bound out of bed at five or six in the morning; likewise die-hard night owls are also rare. Researchers estimate that extremes comprise about 10 to 20 percent of the population, with the rest of us falling somewhere on the intermediate spectrum. And in fact, the majority of us prefer a common point in the 24-hour continuum: daytime.
