You know the types: the early bird who rises with the sun, clear-headed and eager to take on the day. And the night owl, practically comatose if roused before noon, but sharp in the evening.
Whether you’re a lark or an owl affects much more than the amount of coffee you need to start the day. Your circadian type affects cognitive functioning: “The part of the brain that regulates your ability to think clearly and solve problems is heavily influenced by the body clock,” says David Dinges, chief of the division of sleep and chronobiology at the University of Pennsylvania.
An increasing body of evidence also links one’s inner clock to mood fluctuations and fitness; it’s even linked to personality. Morning people tend to be introverts who are conscientious and driven, while night owls are more often impulsive extroverts. Owls also tend to score more highly on intelligence tests and are more likely to be depressed.
After waking up, early birds have higher levels of the stress hormone cortisol than do owls, which may explain their instantly chipper demeanor. Owls’ heart rates are higher in the afternoon than in the morning, which may be one reason why they are sharper mentally and physically as the day goes on. Most telling, many researchers agree, are peak body temperatures, which are linked to reaction time. An early bird’s temperature peaks at 3:30 p.m., while an owl’s rises until 8 p.m.
What sets the body’s clock? The determinants are neither entirely environmental nor entirely genetic. Scientists have pinpointed several genes that indicate circadian type is partially heritable.
An imprinting process after birth is also a factor: Studies show that babies born in autumn and winter tend to be early birds, while spring and summer babies often grow up to be owls. Chronobiologists believe exposure to sunlight affects one’s clock for life. Summer’s long days can set the clock a few hours later, leading to owlish behavior, and short winter days have the opposite effect.
Another factor in the owl-vs.-early-bird breakdown is age: Teens and young adults tend to be owls. But as a result of what researchers suspect is a mix of hormonal changes and cultural factors like uncompromising work schedules, most people steadily move toward early-birdlike behavior as they age.
The best way to make your inner clock work for you? Don’t fight it.
Quiz: Are you an owl or an early bird?
Modern life doesn’t allow most of us to be our true selves. Identify your own body clock.
Always: 5
Sometimes: 3
Never: 1
1. I have a good appetite 20 minutes after waking in the morning.
2. I would have a great workout at 7 to 8 a.m.
3. I find it easy to get out of bed in the mornings.
4. I wake up without an alarm clock on workdays.
5. If I worked between 4 a.m. and 6 a.m., I would choose to sleep beforehand rather than afterward.
6. I am at my very best when I start my day.
7. If I had to take an important test, I would prefer to take it at:
8-10 a.m. (5), 3-5 p.m. (3), 7-9 p.m. (1)
8. If I could choose my schedule, my core working hours would be: 5-10 a.m. (5), 10 a.m.-5 p.m. (3), 5-10 p.m. (1)
Scoring: Total your score and compare them with the scale that follows.
EARLY BIRD
35-40: Extreme early bird
You are among the 10 percent of people who naturally rise by 5 to 6:30 a.m., feeling fresh. You are most productive during the first half of your day, but in the afternoon your mental sharpness steadily declines.
27-34: Moderate early bird
You have many early-bird traits, but perhaps you set your alarm clock “just in case,” or sleep in on your days off. Nights are not off limits for you, but you don’t often stay out late.
DO use sunlight to your advantage. Spend some time outside in the afternoon to bolster your energy during the second half of the day.
DO engage in moderate evening activity – walking or socializing – rather than reading or watching TV.
DON’T accept a night job expecting that you’ll easily adapt.
DON’T exercise within four hours of bedtime.
HUMMINGBIRD
22-26: You are neither
Chronobiologist Michael Smolensky refers to your more flexible type as a “hummingbird.” You tend to be ready for action both morning and night, in sync with our culture’s demands.
NIGHT OWL
14-21: Moderate owl
While you don’t consider yourself nearly nocturnal, you do prefer evenings to mornings. Your mood increases steadily throughout the day. A job that starts at 7 a.m. is not appealing, but a fishing trip at dawn isn’t out of the question.
8-13: Definite owl
If you had it your way, you would sleep till noon. If you hold a 9-to-5 job, you rise as late as possible and usually skip breakfast. At night you find yourself busy, perhaps surfing the Internet, doing the laundry or socializing.
DO open curtains to let the sun wake you.
DO perform your morning routine in natural light.
DON’T stay up late on the weekends or you’ll suffer the effects on Monday, the equivalent of weekly jet lag.
DON’T start new projects or watch TV right before bed. Opt for reading or listening to music.
-Quiz adapted from “The Body Clock Guide to Better Health,” by Michael Smolensky and Lynne Lamberg
