Can you read me one more story?” “I’m hungry.” “I’m thirsty.” Bedtime in my house seems to drag on for two hours, with the kids popping in and out of bed, whining, fussing and only eventually falling asleep. Since they were babies I’ve tried cajoling my kids and bribing them to get them tucked in earlier, praying that they’ll grow up fine with less than the pediatrician’s recommended 10 to 12 hours. I fear they’ve inherited my late-night habit. Scientists have determined that the sleep-wake cycle is regulated by our exposure to light and dark. But it takes time for these rhythms to develop—hence, the irregular sleep of newborn babies. Research (and life experience) shows that sleep rhythms begin to develop at about six weeks, and by three to six months most infants have a regular sleep-wake cycle. While it might not seem like it at three a.m. when you’re walking the floor with a colicky baby, by the age of two most children will have spent more time asleep than awake. In fact, a child will spend 40 percent of his or her childhood asleep. During early development, sleep is the primary activity of the brain. And while sleep is important for all of us, it’s especially crucial for children since it directly affects their physical, mental and emotional development. Sleep researcher Dr. Avi Sadeh of Tel Aviv University studied fourth- and sixth-graders, some of whom were instructed to stay up late for three consecutive nights.
After the third night, a researcher went to the school in the morning to test the children’s neurobiological functioning. The test they used was highly predictive of both achievement test scores and teachers’ ratings of a child’s ability to pay attention in class. Dr. Sadeh found that every hour of missed sleep was the equivalent of losing two years of cognitive maturation and development. In other words, a sleepy sixth-grader will only perform as well as a fourth-grader. Dr. Monique LeBourgeois, director of the Sleep and Development Laboratory and assistant professor of integrative physiology at the University of Colorado Boulder, found that pre-kindergartners who went to bed an hour later on the weekends scored seven points lower on IQ tests. Examining when and how children sleep, along with their functioning when bedtimes and naptimes are altered, her research confirms the importance of getting enough rest to ensure proper development. “Early sleep difficulties are associated with concurrent attentional, emotional and behavioral problems…and predict the onset of such problems in later childhood,” she says. “Just like nutrition and exercise, sleep is critical for good health.” LeBourgeois recently conducted a first-of-its-kind study focusing on the association between children’s internal body clocks and their difficulties settling in at bedtime.
Not surprisingly, children who are put to bed when they aren’t really tired—that is, when their bedtimes are imposed by parents for other reasons and don’t match their internal body clocks— take longer to fall asleep. Around 25 percent of young children have trouble settling in at night, getting out of bed repeatedly for a glass of water or snack or to use the bathroom. As every parent knows, an active child will fall asleep faster. A recent study conducted in Australia and New Zealand found that for every hour a child is sedentary, it takes an additional three minutes to fall asleep. But this doesn’t mean, as I first assumed, that children should simply be allowed to stay up later doing calisthenics. There are many ways to help kids tire earlier, primarily by regulating light at night and in the morning. Dr. LeBourgeois shares some of her findings and insights with Ami readers.
Why is sleep so important for young children? The data clearly indicate that not getting enough sleep in the early years is a predictor of obesity, childhood depression and anxiety. Inability to sleep is also a cardinal feature of many behavioral issues, educational struggles and mental health disorders.
Early childhood is a time when many sleep disorders first develop, including settling difficulties. Research shows that 14 percent of infants, 42 percent of threeyear-olds and 50 percent of five-year-olds resist bedtime. That’s half of all children!
What got you interested in studying sleep, specifically in children? When I was a graduate student in clinical psychology, I specialized in children’s issues. I was also fascinated by how treating sleep problems could improve certain mood disorders. At one point I was working with a patient who was suffering from depression and insomnia. The insomnia was really at the heart of the problem, making the depression difficult to treat. I collaborated with a sleep specialist who later became my mentor. When I saw what a big role sleep played in mental and emotional health, I switched fields from a clinical approach to a scientific one. I fell in love with sleep! Interestingly, I noticed that there was a big gap in sleep research. While there was extensive literature on how too little sleep affects adolescents and adults, there was little information about the internal circadian clock functions in young children.So far, we’ve studied the circadian system in healthy toddlers who are good sleepers, nap regularly and have a consistent bedtime.
Next we’d like to include toddlers who aren’t good sleepers or who are at risk for sleep and mood disorders. Our dream is to track sleep patterns over several decades to understand the longterm impact of sleep.
How are these studies conducted? How do parents even learn about them? We use a number of different methods, including community outreach and laboratory website advertisements to draw parents’ interest in participating in our studies. We screen the parents over the phone and through questionnaires. Once they’re approved, the children wear activity monitors on their wrists to detect when they’re sleeping. Caregivers keep diaries and call the lab every day to report their sleep and wake times. We also have kids participate in activities to measure their ability to control and express their emotions after their regular nap and also when they’ve gone without one.
Why do some kids have trouble falling asleep? If your child is resisting bedtime or having problems drifting off, it’s likely that he or she is not physically ready for sleep at that time. The question is, what can a parent do about it? Sometimes parents choose bedtimes based on their own perceptions about sleep and perhaps their own needs. When kids are put to bed too early, lying in bed awake for such a long time can lead to the association of bed with arousal rather than sleep.
This response may increase children’s lifelong risk of insomnia. Melatonin is a hormone that is secreted by the body in response to darkness that has been linked to the regulation of circadian rhythms. Kids who were put to bed before their levels of melatonin rose took 40 to 60 minutes to fall asleep. Light is also a big factor. When a child gets out of bed and walks into an illuminated room, the light can suppress the production of melatonin and delay sleep. Dimming the lights at night can influence a child’s physiology and help induce tiredness. Also, waking up to light in the morning is important for keeping the circadian system on track. We know from studies with adults that the internal clock can be shifted by exposure to light at specific times of the day. Evening light delays the clock, while morning light advances its timing and helps kids go to sleep earlier. Of course, genetics also plays a part in how much sleep a given individual will need; there’s truth to the phenomenon of night owls and early birds. In fact,healthy bedtimes for kids can vary widely, anywhere from 6:15 p.m. to 9:00 p.m. depending on age and the individual child’s melatonin level. How is that determined? In general, melatonin levels begin to rise before sleep, peak during the night or early morning, and fall to daytime levels before the person wakes up.
One of the things we did in our study was to darken the children’s room in the afternoon. We then had them chew on a dry cotton roll for about a minute every half-hour for six consecutive hours to measure the melatonin levels in their saliva. These levels reflect the timing of their internal body clocks, with increased levels initiating physiological processes in the body that promote sleep. Most children were asleep within an hour of melatonin onset. How can parents tell if their children are ready to go to sleep? Pay attention to what they are doing. Rubbing their eyes and yawning are good indicators. When these signs are detected before bedtime, parents should lower the light level to increase the chance of a smooth transition to sleep. How should a parent handle bedtime with children of different ages? We found that the average onset time of melatonin differed by age. For toddlers it was around 7:30 p.m. and for school-age kids around 8:30. Adolescents didn’t experience it until 9:30 p.m.
In recent years it’s become popular to administer melatonin to young children who have a hard time going to sleep. Is that safe? Melatonin is a hormone and isn’t regulated by the Food and Drug Administration.We don’t know the effects it has on brain development.
What can parents do to encourage a good bedtime routine? Be consistent and engage the child in calming activities. Avoid electronics around bedtime since the special type of light they produce triggers wakefulness. Dim the lights. And make sure that blackout shades aren’t preventing your child from getting needed light in the morning.
What’s your next project? I’m currently starting a study of kids at risk for sleep and mood problems. As we can now assess melatonin onset in young children, we can begin to answer key questions about circadian rhythms and school readiness. Daytime tiredness often manifests as increased activity, aggressive behavior, impulsivity, poor concentration and inattention. Further examination of the association between circadian rhythms and school success could have implications for parents and educators. The goal is to understand the specifics of how sleep, or the lack of it, affects mood, weight and well-being as a child grows into adulthood.