Sleep — too little? too much? — seems to be a perennial concern for parents, teachers, and others who care about children’s well-being. In fact, sleep plays a complicated (and incompletely understood) role in development. However, the benefits of adequate sleep are evident in both physical and mental health. Many communities have debated the merits of moving to later school start-times to better accommodate the typical sleep patterns of adolescents in particular. The recent release of new data from an ongoing federally-sponsored survey prompts us to take a closer look at what we know about this topic.
1. Most children are getting adequate sleep.
For infants, around 13 hours per day is average; a typical school-age child sleeps around 10 hours per night, and teens about nine. However, there are substantial individual differences at all ages. There is no consistent evidence that children or adolescents are getting less sleep now than in the past; in fact, adolescents and young adults report somewhat more hours of sleep now than they did a decade ago. Remarkably, there is no scientific consensus on the specific amount of sleep children (or adults) need.
2. Sleepiness can be a warning sign.
Although the specific role sleep plays in human biology is incompletely understood, inadequate sleep (as indicated by daytime sleepiness) has negative effects on multiple areas of performance and well-being. Both the duration of sleep and its quality are associated with children’s health and behavior, including their school achievement, risk for injury, emotional well-being, and overall health. There is good evidence that sleepiness, regardless of its origins,puts children and youth at risk for unintentional injuries and, for adolescents who are drivers, increases likelihood of motor vehicle crashes. Young people ages 16 to 29 are the group most likely to be in crashes where the cause was the driver falling asleep.
3. The relationship between short sleep duration and overweight is controversial.
Children who are overweight tend to sleep less, and vice versa. Multiple studies, both cross-sectional and longitudinal, report a significant association, especially for boys, and for children younger than five. However, there are many confounding factors that cannot be easily ruled out, and the relationship between overweight and insufficient sleep might go both ways. Nevertheless,there is sufficient evidence for a number of researchers to recommend that we look seriously at improving sleep as a strategy for preventing obesity.
4. Use of electronic media, particularly in the bedroom, can lead to poor-quality sleep.
Children’s use of cell phones, tablets, computers, and TV close to bedtime, and especially having such media in their bedroom, is associated with poor-quality sleep. There may be multiple factors underlying this relationship: the stimulating nature of some media, the displacement by electronic media of time for physical activity, and others.
5. Adolescents may benefit from later school start-times.
In adolescence, normal shifts in their biological clock result in a later-to-bed, later-to-rise pattern. Early school start-times, job responsibilities, or extracurricular activities can conflict with this natural pattern, leading to sleep deficits and poor academic performance.Teens often use weekends to catch up on sleep. For example, the average high school student gets 8.6 hours a night on school days, but 10.9 hours a night on weekends. Depending on the specific study, between 20 and 60 percent of adolescents report daytime sleepiness. Setting later school start-times for adolescents is a promising strategy that has gained the endorsement of a number of scientists. Preliminary evidence shows that later starting times are associated with students’ improved attendance, discipline, alertness, mood, and health.