That morning light shining through the bedroom blinds does more than trumpet the start of another day. It triggers our circadian rhythms, telling the body’s systems when to gear up for a new day and when to shut down.
This biological clock stands under pressure from a technological age that often demands people work nontraditional hours.
Others run into clock disorders for less obvious reasons, like hitting puberty.
No matter the cause, getting the body back in rhythm can be an important component of overall health. With the annual “fall behind” clock change scheduled for this weekend marking the end of daylight-saving time, that rhythm might be a little harder to find.
District neurologist Dr. Marc Schlosberg says humans take their cues from the light and the dark but that biological clocks tick a bit longer than the standard, 24-hour day.
Isolation experiments conducted on both humans and animals, in which someone or something is put in a room with no lights or environmental cues, reveals “the body cycles in somewhere around a 25-hour rhythm,” Dr. Schlosberg says.
“The rest of us cycle on a 24-hour cycle. When the light hits the retina, it resets the circadian clock,” he says.
That’s why odd-shift workers, who toil into the morning hours, have trouble sleeping when their day is done even if physically exhausted.
“You’re exposed to sunlight on the way home,” he says. “Shift-work disorder is really a condition in which you’re trying to squeeze your own normal cycle into an abnormal environment.”
Dr. Schlosberg, co-director of the Washington Hospital Center’s sleep disorders center, says getting out of one’s circadian rhythm can result in slower reaction times and other symptoms common to sleep deprivation.
Not everyone crumbles under the weight of an unconventional work schedule.
“Some people just tolerate this sort of thing better than others,” he says. “But the shift should change so that you’re not doing a night shift absolutely all the time.”
Some shift workers maintain unconventional hours to pay the rent, which puts them at odds with their circadian clocks.
Jim Dillingham, a partner at Shiftwork Solutions in San Rafael, Calif., says such work can lead to moodiness and sleep loss but also less obvious conditions like automatic behavior syndrome.
“You drive home but don’t remember it,” says Mr. Dillingham, whose company helps organizations and workers cope with irregular schedules. “You’re asleep, but you’re doing a routine task over and over again.”
“The problem is you don’t respond to surprises,” he says, recalling a story about a Marine who went on a night march and woke up two miles later in a ditch with a broken leg.
A fully alert person, Mr. Dillingham says, shouldn’t be able to fall asleep in under 18 minutes, he says, adding that as we’re awake our core body temperature rises slightly to help keep us alert.
Workers who want to supplement their sleep time can opt for a quick nap or just 20 minutes of rest.
“Take a 10-minute nap, and you’ll be awake for the next two or three hours,” Mr. Dillingham says, adding an extended shut-eye period could reset the body’s biological clock. “If you sleep too long, the recovery period for a nap is long.”
Dr. Helene Emsellem, director of the Chevy Chase-based Center for Sleep and Wake Disorders, says adolescents often get caught off their circadian rhythms.
Studies show more than two-thirds of teens — Dr. Emsellem says she thinks that figure could be as high as four-fifths — suffer circadian clock shifts during puberty.
“This is why adolescents have such a hard time getting up in the morning,” Dr. Emsellem says. “A lot of kids are sleep-deprived during the school weekday. They simply can’t fall asleep till 1 in the morning.”
Making matters worse is how often teens try to make up for lost sleep by waking up around noon come Saturday and Sunday.
That, she says, only perpetuates the problem.
Dr. Emsellem advises teens shut off their cell phones, computers and other distracting doodads before bed time to prepare them for sleep, and on weekends, not sleeping longer than two or three hours past the time they normally wake up on a school day.
One way to adjust a sleep cycle is to take melatonin. The chemical, produced naturally in the pineal gland, is secreted when the body is exposed to darkness. As night falls, the melatonin levels rise, and we become less alert and more sleepy.
The next day, when the sun rises once more, those melatonin levels begin receding.
The District-based National Sleep Foundation says a synthetic supplement featuring melatonin is the only hormone sold in this country without a prescription.
For questions on how much, when or whether to take melatonin, check with your physician.
People who have trouble sleeping often take melatonin to help them sleep, according to the foundation’s 2002 sleep study. It showed that 74 percent of all Americans fall into that category.
The foundation also says its Web site page featuring melatonin information is one of its most frequently visited pages.
If taken at the appropriate time, melatonin can advance or delay the sleep/awake cycle, the foundation says.
Dr. Al Lewy, vice chairman of the Oregon Health & Sciences University’s psychiatry department in Portland, says circadian rhythm study isn’t reaching a wide audience yet.
“It’s not yet to the point where it’s in the lexicon of the clinician, let alone the patients,” he says.
Frequent fliers, on the other hand, shouldn’t wait for the rhythms to gain mass exposure.
“If you’re going six times zones to Frankfurt without paying much attention it, it’ll take a whole day to adjust for every time zone you’ve crossed,” Dr. Lewy says. “If you pay attention to your lighting environment and take melatonin, you can cut it down to a day or two.”
Circadian rhythm study began roughly 25 years ago, he says, with a published paper showing bright light suppressed melatonin production.
That discovery led to advances in diagnosing, and treating, winter depression, a common form of seasonal affective disorder that can cause fatigue, weight gain and fluctuating appetite levels.
Using an understanding of circadian rhythms to study and treat depression is another matter. Researchers are grappling with the concept with published reports coming soon, Dr. Lewy says.
“In depression, the theory has always been that it’s an internal mismatch between different sets of circadian rhythms,” he says.
“It’s like a symphony orchestra. They all have to keep their beat to the conductor. If some of the instruments are not keeping up, there’s this cacophony. … We haven’t figured out which rhythms are key that have to be in phase with each other, but we’re making progress.”
One group for which circadian rhythms play a more pertinent role is the blind, Dr. Lewy says.
“Without light coming in, their rhythms drift another hour each day,” he says. “A daily dose of a small amount of melatonin can cure that disorder … help them sleep better and feel better.”