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Sleeping Like a BabyA PEEK INTO BABY'S NIGHT LIFE
By Avi Sadeh
Yale University PressCopyright © 2001 Abraham Sadeh
All right reserved.
Chapter One"Why do we sleep?"
The Significance and Role of Sleep
The newborn, in the first days of life, spends approximately two-thirds of each twenty-four-hour period asleep. Over the course of a lifetime, the length of sleep decreases until old age, when humans spend only about a quarter of a twenty-four-hour period asleep. Over the course of our lifetime we spend about one-third of our time sleeping.
There are those who view sleep as a waste of time and those who view it as an unfettered pleasure. Some sleep many hours, and others, few. There are those who awake early and go to sleep early and others who are night owls. It doesn't matter to which camp we belong-sleep is an integral part of our lives.
It often seems that the question of why we sleep is utterly unnecessary, for we all know what happens when we try or are forced to shorten or refrain from sleeping for one reason or another. The primary and strongest expression of lack of sleep is a growing desire to sleep, which becomes increasingly hard to fight. If we refuse to respond to the subtle signals that it's time to sleep, the physiologic need canoverrule our resistance. The need to sleep is so strong that sleep deprivation is often considered to be the most excruciating form of torture. Indeed, many parents begin to relate to their sleepless baby as an Inquisitor who intentionally prevents them from sleeping in order to make them suffer.
But the irresistability of sleep doesn't explain its role. Many years of research in the field of sleep and the ramifications of sleep deprivation have left many questions unanswered. We know that animals that are deprived of sleep for an extended period of time become exhausted and die. We know that sleeplessness gradually damages our subtler mental functions of attention and concentration, and then wider functions of information processing, learning, and memory. We know that in cases of continued sleep deprivation the immune system's ability to respond weakens and physical health is damaged. On the basis of hundreds of studies we can conclude that sleep is a physiologic need analogous to the need for nutritious food. Just as one can go on a diet and control, to some extent, the amount of food ingested, it is possible to change sleep patterns to a certain degree. But severe sleep restriction, like a severe diet, will lead to significant functional damage.
All animals known to us must sleep, or at least spend some of their time in what resembles a state of rest or sleep. Modern research has revealed essential differences in the sleep of various animals and has shed light on brain activity during sleep. Many species of bat, for example, sleep nineteen hours out of twenty-four, as opposed to the giraffe, which sleeps a mere two hours per day. Dolphins sleep in a surprisingly clever way. At any given time, only one hemisphere of the animal's brain is asleep, while the other half is awake. In this way, a certain level of alertness and attention to the environment is always maintained, even during sleep.
The sleep pattern of dolphins illustrates that sleep is adapted to both the physiologic and the environmental needs of an animal. Sleep is precarious for helpless animals who are unable to hide or protect themselves. They live in fear of unpredicted predators. Nonetheless, field studies reveal that some sleeping animals succeed in escaping from seemingly imminent destruction by using senses that remain active. Certain characteristics of sleep, such as the amount of dream-sleep (a dangerous state for an animal), change fundamentally when a high danger of predation exists.
The fact that babies need so much sleep is evidence, perhaps, that they have a limited ability to be awake, or that they have heightened needs for rest and recuperation from wakefulness. Many theories have been proposed to explain the different sleep needs among diverse animals over the course of development. For instance, research on animals provides evidence that an animal's physical size is directly related to the amount of time it spends sleeping. As the animal's physical size increases, its need for sleep decreases. In addition, animals that sleep less live longer. Finally, some theories relate amount of sleep to the body's hormonal status, to the maintenance of body temperature, to energy conservation, and so on. Without attempting to explain these complex theories, we can say that when a baby sleeps, she disconnects, to a certain extent, from the environment that bombards her with stimuli. She sinks into a state that resembles, in many ways, her former fetal state. This protected state simultaneously allows physical rest and brain activity that aids in brain maturation and develops functions of processing and storing information received during wakefulness and recorded in memory.
We might fancifully speculate that evolution was considerate of parents: it treats them to a grace period so that they can gradually get used to their baby. The baby's abundant sleep in the first months gives parents some free time in which to recuperate from the demanding and all-encompassing job of caring for baby.
Chapter Two"What's so interesting about a sleeping baby?"
What Sleep Is and How We Can Peek into a Child's "Night Life"
What is simpler than looking at a sleeping baby? Parents do so day and night, to ensure that baby is well, or purely for the pleasure of it. Every experienced parent can report interesting impressions of baby's sleep: "He doesn't stop moving," "She smiles so that you can see the whites of her gums," "She starts the night on one side of the crib and ends up on the other side," "He snores louder than his father," and so on.
When scientists look at sleeping babies, they do so to understand normal child development and early childhood sleep disturbances. In the first year of life, the baby is limited in her ability to demonstrate her mental abilities and talents. Hence researchers need sophisticated research methods in order to ascertain this information. Using these methods, we can witness more and more abilities of young babies that we knew nothing about in the past. The perceptual and intellectual abilities of the baby, for example, were discovered via such methods. These abilities exist from the first few weeks of life and, among other things, enable the baby to relate to one significant figure who cares for her, usually her mother.
Many studies show that the human baby is visually perceptive and selective. The baby focuses on characteristics of stimuli that resemble human facial characteristics more than those that do not. It has also been found that attention to sounds is selective and that babies only days old prefer human voices to other sounds. These preferences, which exist for other sensory systems as well, show that the baby is "programmed" to home in on human contact. A baby's sleep-wake patterns result from one of his world's most complex systems, which can be studied in a simple and direct fashion from the baby's first few days of life. As with patterns of eating, attention, social behavior, and movement, sleep patterns are an important sign of nervous system maturation and of the child's behavioral organization. The study of sleep in childhood facilitates our understanding of the importance of sleep in the developmental process and the relation between sleep-wake patterns and various other functional systems. Sleep patterns are influenced by neural and bodily systems, by environmental stimuli, and by family patterns. They offer a vast field for the study of the relations among all these complex systems. As a result, the study of sleep is a major subject in interdisciplinary research, involving biologists, physiologists, pediatricians, neurologists, heart and lung specialists, digestive system specialists, and developmental and clinical psychologists.
One of the central fields for understanding sleep in childhood is research that investigates the sources and reasons for common sleep disturbances. Approximately 20 to 30 percent of all babies and their parents cope with sleep disturbances, especially difficulties falling asleep or frequent and lengthy awakenings during the night. In order to assess sleep disturbances and to treat them, we must study and understand normal developmental processes. This understanding of sleep helps us answer basic questions related to sleep disturbances: What is abnormal, and at what age? Are sleep problems solved by the passing of time? Is treatment intervention necessary? Is treating sleep problems effective, and which treatments are most appropriate and effective?
In a typical discussion parents talk about when the baby falls asleep, when she awakens, when she naps, and how she refuses to sleep at night. The most basic common discrimination in these discussions is between sleep and wakefulness. Parents usually relate to the length and frequency of each condition over a twenty-four-hour period. However, are these two conditions all-inclusive?
The breakthrough that made the study of sleep a unique scientific field was also a result of looking at sleeping babies. In the early 1950s Eugene Asrinsky, a young student who worked with a professor of philosophy named Nathaniel Kleitman, observed the appearance of rapid eye movements that could be easily identified even though the babies' eyes were shut. Asrinsky and Kleitman found that while a baby sleeps, cycles of two distinct patterns alternate over the course of a night: quiet sleep, with steady and deep breathing and relatively no body movements, and "active" sleep, characterized by rapid eye movements, rapid body movements, and twitches, mostly of the fingers, toes, and face muscles.
This discovery of active sleep-also called stormy sleep or dream sleep or REM sleep, for "rapid eye movements"-as opposed to quiet or non-REM sleep, was a breakthrough in the understanding that sleep is not a homogeneous process which takes place over the course of a night. Rather, the process comprises a series of distinct physiological states. When adult REM sleep was studied in the laboratory, people who were awakened from this state of sleep tended to remember dreams and to report them (hence the term "dream sleep"). It became clear that the activities of both brain and body in this type of sleep physiologically more closely resemble wakeful activity than quiet wakefulness or quiet sleep.
Parents of babies can easily discern dream sleep, which frequently is evidenced immediately after the baby falls asleep. Her eyes dart about, her fingers or toes twitch rapidly or suddenly, and short smiles, grimaces, or other distortions appear on her face. Looking at a baby and the changes in the stages of sleep leads us to the more important aspect of sleep-the roles of internal biological clocks in the baby's brain. Here is where the appearance of each stage of sleep is determined, timed according to when the baby will feel tired and will be ready to sleep, as well as when he will awaken and feel alert.
Biological Clocks and Sleep Cycles
Many of our bodily functions have cycles or rhythms, according to which certain events recur. When we talk about a biological clock, we are actually speaking of these rhythms.
The term biological clock is, in fact, deceptive. Imagine a clock shop in which each clock was set at a different time, ticked at a different pace, and chimed or buzzed or cuckooed at a different interval. This is a fair analogy to our "biological clocks": our bodies contain many unsynchronized clocks that influence many events and are in turn influenced by them. Perhaps the best known are the sleep-wake clock, which completes a cycle approximately every twenty-four hours, and a woman's ovulation, which completes its cycle in approximately one month. It is important to recognize that these clocks are interrelated. Each is regulated by environmental stimulation, and the concurrent cycles are part of that environment. The day-night cycle, which is expressed in cycles of light and darkness, passes on information about the seasons of the year, according to the length of the day.
Two basic rhythms are related to sleep. The first is the sleep-wake cycle, which in an adult is a circadian rhythm-that is, approximately twenty-four hours. The span between one event of sleep and the next event of sleep is, more or less, twenty-four hours, and the events of waking from sleep are similarly spaced.
The second important rhythm in sleep is the ultradian rhythm between the various stages of sleep-between active sleep and quiet sleep, for example. This rhythm, which changes over the course of the night, is, on average, sixty minutes among babies and about ninety minutes among older children and adults.
Different Methods for Examining a Baby's Sleep
In order to understand how a baby's sleep is examined and measured, we must establish how we define sleep and what distinguishes sleep from different wakeful states. These definitions remain scientifically controversial. One widely accepted definition describes sleep as a state in which three conditions exist: (1) a significant drop in alertness and response to environmental stimuli; (2) a significant drop in the level of body activity; (3) the partial or absolute disappearance of rational thought processes and of consciousness. But contrary to the intuitive notion that sleep entails a cessation of response to the environment, research has shown that we are responsive to the environment even in sleep. Ultimately, the definition of sleep is largely dependent upon the instrument that is used to examine it.
The Method of Direct Observation
It is possible to study babies' sleep simply by observing it, as many parents do. Indeed, many studies were based on direct observation of a sleeping baby. These studies found that not only does a baby sleep less as he grows older, but he spends relatively less time in active sleep and more in quiet and deeper sleep. The observations, made in the baby's natural setting (usually the crib), allowed documentation of sleep in natural conditions. Because direct observations require great effort, they are usually limited to a few hours over the course of a twenty-four-hour period.
Examining Sleep in the Laboratory
The most detailed physiological data about what happens during sleep are gathered in the laboratory. In an examination of this nature, the child or baby is brought to the sleep laboratory in the evening. Electrodes are attached to specific areas on the body and especially on the head, and the subject sleeps in a secluded room. Young children usually have a parent in the room in order to ease the stress that may be fostered by the conditions of the examination. Sometimes when the child resists having electrodes attached to his head, they are connected after he falls asleep. The nighttime examination is relatively uneventful for most babies, but some exhibit a stress reaction sufficient to compromise the quality of the examination (as well as the quality of the baby's sleep). Because the examination is expensive, it is usually conducted for only one night, and therefore the information gleaned from it is limited because great changes can occur in a child's sleep from one night to another.
Tracking by videotaping, which documents the baby's sleep and parental intervention, is an additional type of sleep examination. The video camera is put above the baby's crib, and her state, movements, and behavior can be filmed. Usually, the recording is based on time-lapse video that condenses the night into one to two hours of recordings. The video also shows parental intervention because it is done in the baby's natural conditions. It supplies much information about his sleep, with minimal disturbance to the family.
Excerpted from Sleeping Like a Baby by Avi Sadeh Copyright © 2001 by Abraham Sadeh. Excerpted by permission.
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