Anatomy of a Lullaby

In Emory's growing sleep research program, scholars encounter mystery and paradox


Vol. 7 No. 4
February/March 2005

Anatomy of a Lullaby
In Emory's growing sleep research program, scholars encounter mystery and paradox

Stealing breath and life
Sleep Apnea

We do have some very good people [in sleep research], and we’re gaining a critical mass to do this kind of work.
Donald L. Bliwise, Professor of Neurology, Program Director, Sleep, Aging and Chronobiology


I think there are valuable things we can learn about how plastic or mutable the circadian system is by looking at people who travel abroad and contend with jet lag, or people from different cultures.
Hillary Rodman, Associate Professor of Psychology


The Power of Sleep
Exploring disorder and disturbance
Kathy P. Parker, Edith F. Honeycutt Professor of Nursing

What’s A Few Drinks Between Friends?
Exploring the ancient drinking party with students
Peter Bing, Associate Professor of Classics

Transforming
and Transformative Knowledge

Practicing what we profess
Karen D. Scheib, Associate Professor of Pastoral Care and Pastoral Theology

Further reading

Endnotes

Return to Contents

In Henri Rousseau’s painting The Sleeping Gypsy, a dark-skinned figure clad in a multi-colored robe rests amidst a barren landscape. In the light of a full moon, a lion warily sniffs the gypsy’s hair, but the gypsy dozes on, unaware of his peril. The image, a concurrence of peaceful solitude and potential danger, mirrors the mysterious nature of sleep itself.

Emory is a relative newcomer to sleep research compared with pioneering centers such as Stanford and the University of Chicago, where rapid eye movement (rem) sleep was identified in 1953. But the scope and breadth of its research and clinical programs have grown steadily over the past dozen years. At the four-bed sleep disorders clinic in Emory Hospital, patients undergo diagnosis and assessment for various sleep-related problems, including sleep apnea, narcolepsy, insomnia, and restless leg syndrome. Another four beds are located at the Wesley Woods Sleep Lab, the country’s only sleep research center based in a dedicated geriatric hospital.

That’s no coincidence. Poor sleep is among the most common complaints of the elderly, and there’s a plausible biological explanation, according to Donald L. Bliwise, professor of neurology and program director of Sleep, Aging, and Chronobiology. With age, the circadian rhythms gradually shift, becoming more at odds with the twenty-four-hour clock by which we order our daily lives. Circadian rhythms are the internal biologic clocks that hold sway over numerous physiological processes and which cycle through slightly more than twenty-four hours. (“Circadian” derives from the Latin circa diem, meaning about a day.) Blood pressure, glucose metabolism, and even physical strength and fatigue wax and wane in lockstep with our circadian cadence, which is orchestrated by a tiny shred of the brain called the suprachiasmatic nucleus, located at the base of the hypothalamus. Anyone who has felt sluggish in the middle of the day, even following a good night’s sleep, has been under the influence of a predictable circadian dip.

The age-related circadian shift and the insistence of the circadian clock was demonstrated in an Emory study in which subjects repeatedly stayed awake for an hour then slept for half an hour over forty-eight consecutive hours. This “disentrainment” from the normal daily routine allowed researchers to isolate the body’s physiological cycles that environmental variables would have otherwise masked. The results confirmed that the circadian cycle gradually changes as we age, indicated by a shift of the body’s daily peak core temperature toward earlier clock times. That’s important because we tend to fall asleep faster and sleep more soundly on the descending curve of the circadian temperature cycle. College students who remain awake and alert deep into the night may simply be responding to their circadian cues. But they pay the price when the inevitable circadian downswing collides with morning classes. Over time, the pattern of disrupted sleep creates a deficit, which eventually must be repaid, regardless of how much coffee is consumed.


Culture versus biology


Researchers do not entirely agree on the degree to which our sleep patterns are hard-wired into our anatomy or are influenced by environmental factors. From an anthropological view, age-related variations in circadian rhythm may help us survive, according to Carol Worthman, Samuel Dobbs Professor of Anthropology. While some members of a group sleep, others remain awake and vigilant. Other cultures Worthman has studied do not impose fixed bedtimes and routinely sleep in groups. Besides napping during the day, individuals may wake at random during the night to chat or sing. In fact, our own cultural notions of sleep are insular, says Worthman, who has recorded an astounding diversity of sleep habits among traditional societies, such as the Gabra of Ethiopia (studied by Emory graduate John Wood), the !Kung of the Kalahari (studied by Emory anthropologist Mel Konner), and the Gebusi of New Guinea’s rain forests (studied by Emory anthropologist Bruce Knauft).

“It’s truly stunning that anthropologists, including me, claim to represent the human condition, yet there’s a third of life that we haven’t studied,” says Worthman. She argues that our own, “lie down and die,” dichotomous and solitary pattern of what we call “normal sleep” may be in part an invention of Western culture that ultimately interferes with the body’s demands. “We may have too narrow a view of what constitutes normal sleep in humans,” she says. “The notion that you have a problem if you don’t sleep in a single, consolidated block of time may be counterproductive.” In other words, sleep problems that plague so many Americans may spring in part from the imposition of rigid schedules onto a biological template ill-designed to accommodate our idealized sleep pattern. “Our own boundary of ideal sleep conditions—solitary, silent, padded—tends to be rigid and therefore makes us more vulnerable to sleep disturbances,” she adds. “That has implications for the study of sleep from a neurophysiological standpoint as well as clinical formulations of sleep pathology and possible treatments for sleep disturbances.”

“This notion that you sleep in an unbroken spell through the night is not necessarily correct,” adds Hillary Rodman, associate professor of psychology, who studies the influence of light on animal and human behavior. In courses she has taught on sleep, she learned that some students adapted well to working through the night, while others stumbled through their days in a constant state of sleep deprivation. “I hadn’t appreciated just how variable, creative, adapted, and
maladapted student and faculty schedules are.”

Rodman hypothesizes that access to round-the-clock stimuli—the Internet, for example—may actually coincide more closely with individual differences in sleep/wake preferences. “The affordances we have nowadays of doing something interesting in the middle of the night could be more in line with the way our brain and behavior evolved,” she says. “What we don’t know is if there are absolutes with regard to sleep. All of a sudden you see that sleep differs under different environmental conditions, and that makes you think that the eight-hour rule is just a stereotype.” Rodman has even considered holding classes in the early evening, when students, as well as researchers, report a resurgence of alertness.

But there’s also evidence that humans are predisposed to sleep for long, unbroken periods, according to Bliwise. In studies in which subjects spent weeks in a controlled environment devoid of environmental cues or clocks, they typically fell into sleep-wake patterns wherein they slept for continuous spells that amounted to a third of their day—though the length of an individual’s day often varied from the twenty-four-hour norm.


Essential for survival, fraught with danger

Sleep is a life force as important as food, water, and shelter. Prolonged sleep deprivation can literally kill us. Yet despite the Western tendency to romanticize sleep as a time of safety and security, it is truly a vulnerable state. In sleep, we detach from the external environment. Heart rate, breathing, and blood pressure decrease, as does core body temperature. Brainwaves slow and become more regular—except during REM sleep, when our eyes flick and twitch rapidly and breathing, heart rate, and brain activity quicken. So strong is the sleep drive that we sometimes cannot stay awake to save our lives, as evidenced by drivers who fall asleep behind the wheel.

“It’s not a great mechanism in terms of survival,” says Jeffrey Durmer, assistant professor of neurology and director of the Sleep Laboratory. “You’re out of touch with the environment and therefore vulnerable to attack.” Some species have developed remarkable defense mechanisms. Mallard ducks, for example, can sleep with only half their brains and with one eye open, allowing them to watch for threats to the flock. Dolphins and whales can do the same. But humans aren’t so equipped. Instead, we build structures and lock doors, or, in communal societies, sleep in groups, where individuals are likely to be more easily roused in an emergency.

Surrounding the uncertainties of how and when we sleep hovers the insistent question of why we must sleep at all. Sleep has been linked to myriad functions essential to survival, including immune protection, growth, and energy production. Sleep also appears to be crucial for learning, consolidating memories, and facilitating lateral associations that don’t otherwise occur; we’re more creative and able to solve problems more readily when we are well rested. Yet no one has come up with a clear answer as to why we sleep.

“Sleep may have something to do with the immune system,” says Durmer. “It may encourage recuperative biological processes through hormonal secretion during certain stages of sleep that are important for growth and healing. But why we have maintained this need for sleep, this quiescent period—one which may have been preserved from worms and flies all the way up to humans and other primates—remains an unanswered question.”
—S.F.