The Mystery of Sleep: Why a Good Night's Rest Is Vital to a Better, Healthier Life


Sleep Requirements in the Life Stages


THE MYSTERY. Why do humans have different sleep needs at different stages of life? Unless they understand what to expect, they can place themselves at risk for sleep deprivation, with its potential to impair school and work performance, and to disrupt the family.

The Case of the Sleepy Teenager

I can always recognize a patient who doesn’t want to be in the sleep clinic where I work. It was 8:00 A.M. The thin young man, about seventeen years old, was sitting slouched in the waiting room wearing a hoodie, sunglasses, and earbuds connected to a smartphone, sound asleep. Sitting next to him, looking very concerned, was a well-dressed woman, presumably his mother. Minutes later in the exam room his story came out, with his mother doing all the talking. The young man had been a straight-A student, and now he was failing high school. His teachers were worried that he might have attention deficit hyperactivity disorder (ADHD) or a disease because he continually daydreamed or fell asleep in his classes. His mother explained that it was a struggle every morning to get him out of bed; he could sleep through the ringing of two alarm clocks.

The whole time his mother was speaking, the young man sat texting. (I was amazed that he could see the screen since he still wore his sunglasses.) When she finished, I asked him about whether he snored, had vivid dreams as he was falling asleep, ever awoke paralyzed, or used street drugs, along with a number of other questions that would help me rule out various diseases. The answer was always one annoyed word: “No.” I then asked him whether he thought he had a sleep problem. “No!” His mother looked angrily at him. I asked him to remove the hoodie and the sunglasses, so I could examine him. The high school football insignia on his T-shirt and bags under his eyes told me almost all I needed to know, and when he described his daily schedule, it confirmed my suspicions.

Sleep Needs of Children

From birth, every child has individual sleep needs and patterns. These patterns change with time, and the way the patterns change is also individual. If a couple’s first baby is a great sleeper, this does not mean that future children will be great sleepers. Yet despite individual idiosyncrasies, children tend to have similar sleep needs and patterns at the same ages, and parents who understand what to expect and learn their child’s sleep pattern can recognize when problems arise and when to seek help. In 2015 the National Sleep Foundation published a report (summarized in the figure below) listing recommended hours of sleep for nine age groups, from infants to the elderly.


Sleep patterns change tremendously in the first few months of life. At first, neither the baby nor the parents sleep through the night and the parents experience sleep deprivation. This can be a difficult time for all. It is also the time when a small number of mothers may experience postpartum depression, which can be very serious and often requires treatment. Most parents find relief only after the baby begins to sleep through the night.


Hours of Sleep Needed a Night, by Age

Newborn babies have many sleep periods over the course of a twenty-four-hour day, most of which last between a half hour and three hours. As the newborn does not distinguish between day and night, it awakens many times throughout a typical night. By six weeks, nighttime sleep episodes have become longer, and a more regular sleep pattern usually begins. The baby will sleep a total of fourteen and a half hours on average, with the range being between ten and eighteen hours. Newborns spend about 50 percent of their sleep time in REM sleep, during which they twitch and grunt and boys may have erections. All of this is normal.

Parents who want to help their baby get the sleep it needs must learn the baby’s language—that is, how he or she communicates signs of sleepiness. For instance, certain cries, fussiness, and rubbing of the eyes signal that the baby is sleepy. Parents should recognize that the baby is tired when they see those signs and put the child to bed. (This would also be a good time for the parents to sleep, unless there are other children who require attention.) Early on parents might rock the baby to sleep, but by the end of the second month, most babies should be learning to fall asleep on their own.

Between two and twelve months, the baby’s nighttime sleep episodes gradually become longer. By four to six months of age he or she will temporarily wake up during the night but should begin to fall back to sleep without intervention from the parents. At two months a baby will take three or four naps over the course of twenty-four hours. By the end of the first year, most babies take two naps a day.

Babies at this age should be put to bed on their back when they are ready to sleep. Do not put a baby to bed every time the baby yawns—not every yawn means the baby is ready for sleep. Parents should learn when their baby will be sleepy and follow that schedule so that they won’t have to wait for the baby to show signs of sleepiness before putting her or him to bed. After the baby is in bed, parents should fight the impulse to check on the child every time she or he awakens, as babies need to fall asleep on their own even in the middle of the night. If the baby begins to associate falling asleep with being held or rocked by a parent, he or she might not fall asleep without this assistance—babies quickly learn that if they cry, the parent will come and rock them. Parents, meanwhile, are thinking, “If I don’t go, the baby will never fall asleep and I’ll never get to sleep. I’d better go.” Parents and baby are now trapped in a vicious circle. This is the time when it is natural for babies to learn to fall asleep on their own; parents should help them achieve this (see Chapter 7).

Babies who sleep more than eighteen hours or fewer than ten, are excessively sleepy or nonresponsive while awake, or exhibit loud snoring or obstructed or stopped breathing during sleep may have apnea. Causes at this age include various abnormalities of the anatomy of the breathing passage or something as simple as enlarged tonsils. Parents who suspect their child has a disorder should contact a doctor. If the baby turns blue, or gray, get medical help immediately as this is a sign of low blood oxygen.


At one year of age, children are still napping, but they do most of their sleeping at night. Naps are generally quite regular. Their sleep time will usually be eleven to fourteen hours a day. By the age of three, they are taking shorter naps. It is during these years that children need to learn good sleep habits.


By the time the child is five, he or she generally will not need a nap. Children age four to thirteen need at least two to three hours’ more sleep than adults. Over the years, I have seen several families whose children were falling asleep in class; the parents could not understand why this was happening because the child was getting as much sleep as they were. But although seven or eight hours of sleep a night is fine for the parents, it is inadequate for a child. All parents and educators should understand that children, from birth through adolescence, need more than the average amount required by adults.

Several sleep problems that can begin when the child is younger can become important issues in the years before adolescence. These include sleepwalking and bedwetting (enuresis). As we shall see in Chapter 14, sleepwalking is common among children, and as among adults, it can be made worse by sleep deprivation. Sleepwalking may be present from the time a child can walk but often becomes an issue later, for example when the child is invited for a sleepover. Sleepwalking generally becomes less frequent as the child grows older. If the sleepwalking episodes do not involve dangerous activity such as going downstairs or leaving the house, treatment is usually not required. Similarly, bedwetting often becomes a problem between ages five and ten. Parents of bedwetters should consult a pediatrician.


Many adolescents go to bed late and wake up late. Before bed, many spend their time in activities such as talking on the phone, playing video games, surfing the internet, or texting that tend to stimulate the brain and make it harder to sleep. The light from the screens of electronic devices may disturb sleep in part by suppressing the production of melatonin.

As a result of these habits as well as the natural tendency of adolescents to go to sleep later in the evening during their teenage years, American children are severely sleep deprived. The 2006 Sleep in America poll found that between the sixth and twelfth grades, teenagers’ sleep time drops from 8.2 to 6.9 hours. Adolescents should sleep more than 9 hours. By the twelfth grade 95 percent of American children are sleep deprived!

The 2011 Sleep in America poll found that texting had become pervasive among adolescents: 72 percent of children ages thirteen to eighteen brought their smartphones into their bedrooms, and 56 percent texted during the hour before they went to bed.


Percentage of Children Who Are Sleep Deprived, by Grade

In most school districts the yellow school buses appear at a time the children should be sleeping. If the child’s schedule results in his or her falling asleep in class or performing poorly, parents should step in and make sure the child does not stay up late, does not participate in stimulating activities right before bedtime, and limits his or her caffeine intake. Parents who find it hard to keep their teenagers away from electronic screens might want to explore other options: some devices allow the user to change the colors of the screen to reduce blue, the wavelength of light that is the most disruptive.

Certain symptoms in sleep-deprived adolescents deserve special attention. Besides the sleep deprivation caused by a lifestyle that interferes with sleep, adolescents may find that their circadian clock changes, so that they are no longer on the same sleep schedule as adults, and this can cause problems (see Chapter 8). When the circadian clock runs late, teenagers go to bed late, have trouble getting out of bed to go to school, and sleep much later on weekends to catch up on sleep.

Teenagers who are extremely sleepy during the daytime and fall asleep at inappropriate times in spite of getting normal amounts of sleep may have a significant sleep disorder, and parents should consult a doctor. At this age, the possibilities include narcolepsy, which classically begins during the teenage years (see Chapter 13), sleep apnea (in a child who snores, the most common causes are enlarged tonsils and obesity; see Chapter 12), and some movement disorders (see Chapter 11). Teenagers who have an iron deficiency can also experience severe insomnia and daytime sleepiness, conditions that improve once the iron deficiency is treated.

Sleep Problems That Start in the Teenage Years

Sleep deprivation

Abnormal circadian clock

Sleep apnea


Movement disorder

Sleep Needs of Adults

YOUNG ADULTS, EIGHTEEN TO TWENTY-FIVE YEARS Young adults, especially college students, are notoriously sleep deprived. They need seven to nine hours of sleep. They stay up late because of their lifestyle (spending time on social media, partying, studying) or because their circadian clock is running late (see Chapter 8) and may have to get up early to go to class. They pull all-nighters to finish projects and prepare for tests. In college classes, especially when there are hundreds of students in the room, as soon as the lights dim, many start to nod off. Students who learn about the importance of sleep and practice healthy sleep habits even during the college years can significantly improve their ability to have a healthy and productive lifestyle. Their success in life depends on these years.


Adults tend to need less sleep than children, teenagers, or young adults. But they do need on the average seven to nine hours a day. Generally the amount of sleep an adult gets is affected by his or her lifestyle, including family, social, and work obligations. Commuting, nontraditional work hours, and late-night time spent on social media chip away at sleep time. The quality and quantity of sleep can be affected by the development of diseases. For example, sleep apnea, discussed later in the book, first becomes symptomatic in people in their forties or fifties.


Percentage of Individuals Texting at Bedtime, by Age


The majority of people in this age group are women, who on average live longer than men. The U.S. Census reported in 2013 that for every hundred women older than age sixty-five there were only seventy-eight men of the same age; for every hundred women age eighty-five or older there were only fifty-one men of the same age. It has been estimated that by 2060 the United States will have a population of 417 million. Of the total it is estimated that there will be 53 million women and 45 million men above age sixty-five. About a quarter of the entire population will be people over sixty-five.

But measuring age only in terms of years can be misleading. When I was a medical student, the average man was dead by the age of sixty-nine, and the average woman by age seventy-four. A person over sixty-five who became critically ill would not even be admitted into the intensive care unit because hospitals were unwilling to expend their resources on patients who were likely to die. Few Americans lived into their eighties, nineties, or hundreds. Today, in spite of air and water pollution, exposure to toxins in food, climate change, and other ills endangering life on our planet, people in the developed world are living longer and are healthier than at any time in the past. We have therefore had to rethink many of our guidelines with regard to best practices for “older” people.

Most important, we need to recognize that aging—deterioration in function related to time—varies from individual to individual. Within any given person, organ systems will age at different rates. Joints and muscles might age more quickly than the mind. Some people in their nineties use computers to trade stocks on the internet, and read several newspapers a day, yet have trouble climbing stairs or going for a walk. For other people, intellectual abilities begin to plummet in their early sixties while their bodies remain active. Some people contract diseases that seem to accelerate the aging process, such as diabetes.

Healthy older people can have normal sleep patterns—they fall asleep quickly, sleep through the night, and are wide awake and alert the next day. A 2003 poll concerning sleep in older people found that many are sleeping better and longer than younger people, and the better the health of older people, the better they slept. Like younger adults, older people need seven to eight hours of sleep every twenty-four hours, but some will start to take naps in the afternoon once they retire from work. They might then have trouble falling asleep at night or they might find themselves awakening very early in the morning. Some of my patients complain about these very early awakenings and ask what they can do to stay asleep until the time they want to wake up. They are surprised to hear that early awakenings need not be a problem if they are alert and functioning during the daytime. They can stay on their current sleep pattern, or, if they would rather change their nighttime sleep, they can try omitting the nap.

Napping can have risks, however; some recent studies have shown that there is an association between napping and long sleep duration with increased heart disease and diabetes. In fact, a tendency to fall asleep in the daytime or at inappropriate times and places can be an important clue that there is something abnormal about a person’s sleep. An eighty-five-year-old woman brought her eighty-nine-year-old husband to see me. He still had his driver’s license, but she was increasingly terrified to drive with him because he could not stay awake while driving. He had to take a fifteen-minute nap halfway through a thirty-minute drive from home to their country club. His excessive daytime sleepiness turned out to be a sign of sleep apnea.

Napping is particularly common in nursing homes. If you visit a nursing home during the daytime, you will often find lines of wheelchair-bound people who have nodded off. The residents of these homes seem to spend a great deal of time asleep. This may be due in part to the fact that they are not provided with enough exposure to natural sunlight, or the rooms may be poorly lit, which causes their circadian clocks to stop working.

Other abnormal sleep patterns may result from a variety of medical conditions, including high blood pressure, heart disease, diabetes, cancer, and depression; some people have one or more of these conditions. The more conditions a person has, the poorer the quality of his or her sleep. For example, people with four or more of these conditions are five times more likely to complain of daytime sleepiness than healthy people are. These diseases are covered in greater detail in Chapter 15. Women become menopausal in their late forties and early fifties, which causes sleep problems. They may also develop medical conditions that affect their sleep. I discuss these issues more fully in Chapter 5.

In addition to the common medical conditions of older people that can lead to sleep problems, many of the drugs used to treat those medical conditions can cause sleep problems. (In Chapter 17 I discuss which drugs cause sleep problems.) Older people are more sensitive to the main effects and side effects of medications than younger people, and both the health care provider and the patient should be informed about the side effects of every medication being considered.

It is also important for older people to be instructed about both the dosage and the regime of any medications prescribed. Sometimes aging patients’ memories are not capable of tracking all this information, so they should make sure that it is written down and accessible. A particular worry is patients who continue to take old prescriptions because the bottles are still around, while also taking updated prescriptions of the same drug. Since many drugs have sleepiness as a side effect, such an unintended overdose of prescribed drugs can cause dangerous sleepiness or even coma.

Back to the Sleepy Teenager

The young man did not have a disease; he simply was not getting enough sleep. When I asked him to describe his schedule over a twenty-four-hour day, he told me that his mother woke him up every school day at 6:30 A.M. He would shower and dress quickly, but he never had time for breakfast before the school bus came at 7:00. School started at 7:30 and finished in the afternoon at 2:30. Then came football practice, from 3:00 to 5:00. His mother would pick him up from practice, and dinner was at 7:00. He often nodded off before dinner, then spent the rest of the evening rushing through homework on a big computer. At 11:00 P.M. he would start preparing for bed, but usually would not be in bed until midnight—and would fall asleep every night holding his smartphone, on which he had been texting. On weekends he would sleep until noon. Like most teenagers, this young man needed nine to ten hours of sleep a night, but his schedule was allowing him to sleep just over six hours. Because his mother, a mature adult, did not need as much sleep as her son, she did not realize that six and a half hours of sleep was simply too little for this stage of his life.

The solution to his problem turned out to be simple: no electronics after 10:00 P.M. and in bed by 11:00. The new schedule did not solve all his problems in school, but it helped. He was more alert throughout the day and his grades soon improved.

At different stages of life we need different amounts of sleep and follow different sleep patterns. Babies need to sleep most of the time, but parents can help them develop sleeping schedules that minimize their own loss of sleep. Teenagers who need to get up for the school bus must be ready for bed earlier than their parents. Older people might begin napping. At any age, failure to get the appropriate amount of sleep can lead to a variety of problems, from poor performance to serious illness. We all need to know how much sleep we need at each age, and this is something that parents, in particular, need to learn so they can help their children have healthy sleeping and waking lives.