By Randy Dotinga
TUESDAY, Aug. 21 (HealthDay News) -- Quiz time: Is it a good idea for high school students to stay up later than usual cramming for that final?
New research suggests it's not: Sleep-deprived studying appears to lead to worse results on tests and also hurts academic performance, researchers report.
The study relies on the perceptions of students about how they performed in school and on tests, not their actual grades. That means there's no way to know if trading studying for sleep actually lowers grades on average or has a smaller, less noticeable effect.
Still, the research does offer insight into the disruptive power of choosing to study late and get less sleep than usual, said study lead author Cari Gillen-O'Neel, a graduate student at the University of California, Los Angeles.
"If you're sacrificing your sleep time, that is actually not helpful. It seems like it's associated with worst functioning the next day," she said, adding, "You should distribute study time evenly across the days of the week and absolutely not let it cut into your sleep time."
Previous research has found that people who sleep more have higher grade point averages, Gillen-O'Neel said, but those studies have looked at a big-picture view. "We wanted to explore that dynamic at a more daily level," she added.
The researchers surveyed 535 high school students from the Los Angeles area, following them from 9th through 12th grade. For two weeks, the students kept diaries on how long they studied, how long they slept and whether they had trouble in school, that is, they didn't understand something in class, scored poorly on a test or got a poor score on homework.
Students reported spending an average of an hour studying each night throughout high school, but they got an average of 41 fewer minutes of sleep by 12th grade compared to 9th grade. And, the researchers noted, in the higher grades, "days of extra studying tend to be followed by days with more academic problems."
So trading studying for sleep appeared to hurt academic performance. "It is not a huge effect, but it is significantly greater than chance," Gillen-O'Neel said. "The size of the effect increases over time and is strongest in 12th grade."
Dr. Phyllis Zee, director of the Sleep Disorders Center at Northwestern University Feinberg School of Medicine, said the research "should make not only high school students -- but also college students -- re-think about the common practice of 'cramming' for exams at the expense of sleep. Prioritize sleep for learning and health! Bust the myth that sleep is dispensable."
But will the message sink in? "One piece of research will clearly not change behavior, if that behavior is perceived to have a payoff," said Kyla Wahlstrom, director of the Center for Applied Research and Educational Improvement at the University of Minnesota, in St. Paul. "But this well-crafted study adds an excellent drop of new knowledge to the 'knowledge bucket' that we have about sleep. Good research is additive -- and if these findings cause one or more persons to think differently about the relationship between cramming and sleep, then it has proven it has power."
The study appears in the current online issue of the journal Child Development.
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