In the study, teachers were not told the amount of sleep students received when completing weekly performance reports. Yet they rated students who had received eight hours or less as having the most trouble recalling old material, learning new lessons and completing high-quality work. Teachers also reported that these students had more difficulty paying attention.
The experiment is the first to ask teachers to report on the effects of sleep restriction in children.
"Just staying up late can cause increased academic difficulty and attention problems for otherwise healthy, well-functioning kids," said Gahan Fallone, the study's lead author. "So the results provide professionals and parents with a clear message: When a child is having learning and attention problems, the issue of sleep has to be on the radar screen."
Fallone will present the findings Nov. 10 at the American Medical Association's 24th annual Science Reporters Conference in Washington, D.C. Results will be published in the December issue of SLEEP, the peer-reviewed journal published jointly by the American Academy of Sleep Medicine and the Sleep Research Society.
Fallone is an associate professor at the Forest Institute of Professional Psychology in Springfield, Mo. At the time the study was conducted, he was a researcher at Bradley Hospital and an assistant professor of research at Brown Medical School.
Research team members and journal article co-authors, are Christine Acebo, assistant professor of research at Brown Medical School and associate director of the Bradley Hospital Sleep and Chronobiology Research Laboratory; Ronald Seifer, director of Brown's Center for the Study of Human Development and director of research at Bradley Hospital; and Mary Carskadon, professor of psychiatry and human behavior at Brown Medical School and director of the Bradley Hospital Sleep and Chronobiology Research Laboratory.
Fallone said that while researchers have studied sleep restriction in teens, few have studied its effects on children - and previous studies were conducted in labs, not classrooms. So the Bradley-Brown team set out to conduct a real-world experiment.
A total of 74 children from Rhode Island and Massachusetts, ranging in age from 6 to 12, participated in the study. Each child was screened for medical and psychological health to ensure that none had sleep disorders or psychiatric illnesses, such as attention-deficit/hyperactivity disorder (ADHD), that can interfere with learning.
Children spent three weeks in the study. For one week, they went to bed and woke up at their typical times. Another week, they stayed up much later than normal. This meant eight hours of sleep per night for children in first and second grades, and six-and-a-half hours for children in the third grade and up. For another week, students followed an optimized routine of no fewer than 10 hours in bed each night. To ensure compliance, subjects wore wrist monitors that log motion both night and day.
Teachers completed a weekly 34-question survey rating students' classroom behavior and performance. Teachers were told that study participants would be sleeping less than usual during one of the three weeks of the study. but they were not told which week that would be.
The results: Teachers reported significantly more academic problems for students whose sleep was restricted, compared to weeks where they followed their own bedtime routine or the optimized schedule. Severity of attention problems also spiked when students' sleep was restricted.
What the study did not find: Sleep restriction causes hyperactivity. No changes were noted in ratings of hyperactive-impulsive behaviors. In fact, researchers found that students were slightly less active at school after staying up late.
Results of the experiment complement a mounting body of evidence that inadequate sleep has negative consequences for teens, resulting in more depression, lower grades and more frequent car crashes due to drowsy driving. At the same time, kids and teens are "losing" sleep to cell phones, computers, television, after-school activities, larger homework loads and increased consumption of beverages such as coffee and caffeinated soft drinks.
With more children being diagnosed with attention disorders and learning disabilities, Fallone said the results act as a reminder that sleep should be forefront in the minds of school psychologists, pediatricians and other professionals responsible for diagnosing and treating these problems.
"If we don't ask about sleep and try to optimize sleep patterns in kids struggling academically, then we aren't doing our job," Fallone said. For parents, he said, the message is simple: "Getting kids to bed on time is as important as getting them to school on time."
The National Institute of Nursing Research and the National Institute of Mental Health funded the research.