A study of nearly 3,000 fourth, fifth, and sixth graders links a mid-day nap with greater academic achievement.
The findings show a connection between 30 to 60 minutes of sleep in the middle of the day and higher IQ; greater happiness, self-control, and grit; and fewer behavioral problems.
The higher IQ finding was particularly evident in sixth graders, scientists report in the study of 10- to 12-year-old children in China.
The most robust findings were associated with academic achievement, says Adrian Raine, professor of criminology, psychiatry, and psychology at the University of Pennsylvania and coauthor of the paper in Sleep. “Children who napped three or more times per week benefit from a 7.6 percent increase in academic performance in grade 6. How many kids at school would not want their scores to go up by 7.6 points out of 100?”
Sleep deficiency and daytime drowsiness are surprisingly widespread, with drowsiness affecting up to 20 percent of all children, says lead author Jianghong Liu, an associate professor of nursing and public health. What’s more, the negative cognitive, emotional, and physical effects of poor sleep habits are well-established, and yet most previous research has focused on preschool age and younger.
That’s partially because in places like the United States, napping stops altogether as children get older. In China, the practice is part of daily life, continuing through elementary and middle school, and even into adulthood.
So, Liu and Raine, Rui Feng, associate professor of biostatistics , and Sara Mednick, associate professor of cognitive science at the University of California, Irvine, turned to the China Jintan Cohort Study, established in 2004 to follow participants from toddlerhood through adolescence.
Who needs a midday nap?
From each of 2,928 children, the researchers collected data about napping frequency and duration once the children hit fourth, fifth, and sixth grades, as well as outcome data when they reached grade six, including psychological measures like grit and happiness and physical measures such as body mass index and glucose levels.
They also asked teachers to provide behavioral and academic information about each student. They then analyzed associations between each outcome and napping, adjusting for sex, grade, school location, parental education, and nightly time in bed.
It was the first comprehensive study of its kind, Mednick says. “Many lab studies across all ages have demonstrated that naps can show the same magnitude of improvement as a full night of sleep on discrete cognitive tasks. Here, we had the chance to ask real-world, adolescent schoolchildren questions across a wide range of behavioral, academic, social, and physiological measures.”
Predictably, “the more students sleep during the day, the greater the benefit of naps on many of these measures,” she says.
Easy and inexpensive
Though the findings are correlational, the researchers say they may offer an alternative to the outcry from pediatricians and public health officials for later school start times.
“The midday nap is easily implemented, and it costs nothing,” says Liu, particularly if accompanied by a slightly later end to the day, to avoid cutting into educational time. “Not only will this help the kids, but it also takes away time for screen use, which is related to a lot of mixed outcomes.”
Future directions could look at why, for example, children with better-educated parents nap more than children with less educated parents, or whether investigating the influence of culture and personality, could advance nap interventions on a global scale. Ideally, a randomized control trial would explore causation questions like whether napping leads to better academic achievement or whether they link in some other way. However, none of this is yet in the works.
For now, the researchers say they hope the results of this current study can inform future interventional work that targets adolescent sleepiness.
The National Institutes of Health, National Institute of Environmental Health Sciences, and the National Institute on Aging funded the work. Additional researchers are from the University of Delaware College of Health Sciences School of Nursing and Shandong University School of Nursing.