Headlines

As reported by The Hartford Courant, January 7, 2006.

Restful Sleep in Two Shifts

By William Hathaway

When you wake up in the dark of night, don't fret. You are doing just what your body was designed to do, some scientists now say - to sleep in a split shift.

Countering the conventional wisdom of some sleep doctors, a few sleep experts say that when you wake up, you shouldn't jump out of bed and read but lie there and enjoy the nocturnal idyll.

This new view of a natural night's sleep in two phases is based on an old view of human behavior - pre-Edison. Before the invention of electric lights, darkness was mankind's companion during long nights, and sleep was typically punctuated by an hour or two of what sleep experts call "quiet wakefulness."

"We come from an environment molded from 3 billion years of evolution, and when we change our behavior, there may be problems," says Richard Stevens, an epidemiologist at the University of Connecticut.

Other sleep experts argue that a two-hour wakeful interlude at midnight might have been fine for Stone Age man, but it ignores the realities of hectic modern life - when people are lucky to get anything close to eight hours with their heads on a pillow.

"It's a great theory, but if you try to apply it today, you could set yourself up for more trouble," says Dr. Daniel McNally, director of the UConn Sleep Disorders Center. "People get up in the night and say, `Well, I should just lie here and go back to sleep.' But in most cases, that is not what is going to happen. People find themselves awake; they worry about it, focus on it, and it goes from a calm experience to anxiety-inducing stress."

Some of the few anthropological studies that have examined sleep behavior in more primitive cultures suggest that we may be designed to sleep in two shifts, broken by a short interlude of wakefulness. And modern-day folks can revert to that default sleep-setting easily.

Researchers at the National Institute of Mental Health asked 15 subjects to rest and sleep in darkness between 6 p.m. and 8 a.m. for several weeks. For a few days, the subjects slept for 11 hours at a stretch, apparently catching up on lost sleep. But then they fell into a pattern of lying awake quietly for a few hours before falling asleep for three to five hours and then waking for about an hour. Then they slept for another four hours.

During the quiet but wakeful times, the subjects also secreted elevated amounts of the hormone prolactin, which promotes a state of calmness.

Some sleep experts paint a portrait of nocturnal bliss, when our ancestors - sans Jay Leno or the Internet - hit the sack early and awoke for a midnight chat or reflected upon their dreams or indulged themselves in a late-night dalliance before slumbering toward morning.

In the last few decades, scientists have shown that a proper night's rest, usually considered seven to nine hours a night, is important for maintaining the immune system and avoiding obesity and diabetes.

Stevens suggests that "biphasic" sleep patterns may also promote the production of other beneficial hormones.

"The whole process of going in and out of sleep may be natural and important," says Stevens, who has conducted studies that suggest the prolonged exposure to the electric lights of modern life may be one reason why the incidence of breast cancer has increased slowly and steadily during much of the past century.

So, is waking up in the middle of the night part of our biological history?

"It very well might be, but I don't think the evidence is convincing," says Dr. Daniel Kripke, a sleep researcher and psychiatrist at the University of California, San Diego.

On the other hand, "I don't think there is any evidence that it is harmful."

McNally says he is willing to accept the theory of biphasic sleep, and in fact he tells his patients that waking up in the middle of the night is natural. But he also says that for most people with sleep disorders, that isn't very helpful.

For both practical and cultural reasons, most Americans define a good night's sleep as an uninterrupted one.

"The dilemma for us in the real world is that it is all too easy to fall into irregular sleep habits and not respond to our body's needs," McNally said. "The big problem is that there is such a strong expectation that to sleep through the night is good, and to wake at night is bad. People feel like they have a right to a good night's sleep, and if they have a problem, there is an advertisement right there on television with someone saying you don't have to lie awake at night. And when you are lying there suddenly wide awake, the bed seems to tell you to be tense. You worry about it and become stressed."

McNally suggests a compromise for those folks. Get up, but avoid bright lights. And don't go back to bed until you are sleepy.