"Our results have significant clinical and educational implications," says author Avi Sadeh, D.Sci., of the department of psychology at Tel Aviv University in Israel. "They highlight the need for parents and professionals to be aware of the consequences of insufficient sleep in children and the potential benefits of sleep extension."
Previous studies of adults have found that sleep deprivation significantly impairs the brain's executive control system, which helps people organize, prioritize and focus on tasks. But few sleep-deprivation studies have focused on children, and those few have tended to examine extreme rather than modest sleep deprivation.
"The daily struggles between children and their parents usually occur at home and are often limited to modest changes in sleep," Sadeh says. "Persistent battles on topics such as 'just one more TV show' raise the scientific question: 'What difference does an hour make?'"
To help answer this question, Sadeh and colleagues studied the effects of adding or subtracting one hour of sleep on 77 children in fourth and sixth grades. In addition to keeping a log of sleep-related information such as lights-off time and the number of times the kids woke up during the night, each child wore an actigraph, a device on the wrist that detects movement. Information gleaned from the actigraph was used to determine the children's sleep schedule (the time they fell asleep and the duration of sleep) and sleep quality (how many time they woke up during the night and how long they were awake).
For the first two nights of the five-night study period, the children adhered to their normal sleep pattern, and for the last three nights the children were asked either to extend or reduce their sleep time by one hour.
At the start and end of the study, the researchers also gave the children several tests of neurobehavioral functioning. These tests, administered on a laptop computer, included measures of finger-tapping speed; reaction time to the appearance of a large square onscreen; responsiveness to a specific animal presented onscreen; and recall of sequences of digits.
Children who got an extra hour of sleep actually experienced more night-wakings and a decreased percentage of sleep. Reducing sleep by one hour had the opposite effect: It resulted in decreased night-wakings and an increased percentage of sleep, the researchers found.
Previous researchers have identified these effects as the body's way of adapting to sleep loss, but in this study, the sleep-deprived children reported significantly higher fatigue ratings in the evening. In addition, their performance on several of the neurobehavioral tests compared unfavorably with the children who received an extra hour of sleep. The sleep-deprived children's performance on the reaction time test suffered, and their performance on the recall and responsiveness tests remained stable, while the children with the extra hour of sleep improved their performance on these tests.
These findings suggest that "moderate changes in sleep duration have detectable significant effects on children's neuropsychological functioning," Sadeh says. The study results are published in the March/April issue of Child Development.
"Previous studies have suggested that children today are getting less and less sleep over the years -- that is, less than children a decade or two decades ago were," Sadah notes. "There are good reasons to believe that with today's nightly temptations (TV, Internet, and other aspects of social life and acting like grown-ups by staying up late), many children are chronically sleep-deprived."
The researchers note that their study findings cannot, unfortunately, give a clear answer as to how much sleep children need at different ages.
"Parents and child-care professionals can explore the appropriate sleep needs of a specific child by experimenting with extending or restricting sleep, tracking the changes in the child's behavior and well-being, and finding the child's optimal sleep needs," Sadeh concludes.
This study was supported by the Israel Ministry of Education and by Helene and Woolf Marmot.
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By Ann Quigley, Contributing Writer
Health Behavior News Service