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Rebecca Goldin Ph.D, January 23, 2010
How much difference does a little bit more or a little bit less sleep make?

Lack of sleep for adolescents has been an ongoing complaint of parents everywhere. There is substantial evidence to back up the need for more time spent in a horizontal position. Kids who sleep less suffer from a variety of problems: reduced memory retention, more depression, and more accidents. Depression and suicidal thoughts have yet again been linked to less sleep, though of course a causal link has not been established. Sleep is known to affect problem solving skills as well as self-reported traits of emotional intelligence. It is also correlated in children and adolescents to being overweight.

While more sleep may help teens deal with life better, it may not be a panacea either. A recent study showed that IQ was a much stronger predictor of academic success on math and reading achievement tests than sleep patterns. However, the study did not consider the possibility that poor sleeping is correlated with lower IQ. In fact, sleep disordered breathing symptoms (noisy sleeping, snoring or sleep apnea) were associated with worse performance on memory and an intelligence test (the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R)) in 5-year-olds.

In other circumstances, sleep did have an impact on school performance. A lot of attention has been focused on Minneapolis public schools. When they delayed their high school start times by 1 hour and 25 minutes in 1997, the results were impressive: improved attendance and enrollment rates, less sleeping in class, and less student-reported depression. Grades also went up, though the benefit was not statistically significant and there were many problems with the data (missing data, grade inflation, changing teachers, courses with different names, no clear rubrics, etc). Take a look at the report from the study here.

The problem of sleep deprivation is not just American; compared to the U.S., Chinese children sleep about an hour less per day; and there is, in general, quite a big difference in sleep duration among students from different countries. The Swiss seem to have the record, as their high school students sleep an average of nine hours per day. In the U.S. it’s seven to eight hours a day.

Sleep deprivation is a known cause of automobile accidents and has a measured negative impact on alertness and performance.  Luckily, in sleep-deprived adults, caffeine has been shown to have a positive impact on “pscyhomotor vigilance speed” and alertness; but since it only lasts 2-4 hours, it won’t get someone through school.



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