The performance gap caused by an hour's difference in sleep was bigger than the gap between a normal fourth-grader and a normal sixth-grader. Which is another way of saying that a slightly sleepy sixth-grader will perform in class like a mere fourth-grader. "A loss of one hour of sleep is equivalent to [the loss of] two years of cognitive maturation and development."
Perhaps most fascinating, the emotional context of a memory affects where it gets processed. Negative stimuli get processed by the amygdala; positive or neutral memories get processed by the hippocampus. Sleep deprivation hits the hippocampus harder than the amygdala. The result is that sleep-deprived people fail to recall pleasant memories, yet recall gloomy memories just fine.
Teenagers suffer the most:
Brown's Mary Carskadon has demonstrated that during puberty, the circadian system--the biological clock--does a "phase shift" that keeps adolescents up later. In prepubescents and grownups, when it gets dark outside, the brain produces melatonin, which makes us sleepy. But adolescent brains don't release melatonin for another 90 minutes. So even if teenagers are in bed at ten p.m. (which they aren't), they lie awake, staring at the ceiling.
Awakened at dawn by alarm clocks, teen brains are still releasing melatonin. This pressures them to fall back asleep--either in first period at school or, more dangerously, during the drive to school. Which is one of the reasons young adults are responsible for more than half of the 100,000 "fall asleep" crashes annually.
The schools don't help:
While the evidence is compelling, few [school] districts have followed this lead. Conversely, 85% of America's public high schools start before 8:15 a.m., and 35% start at or before 7:30 a.m.
But of all the arguments [Dr. Mark Mahowald, Director of the Minnesota Regional Sleep Disorders Center has] heard, no one's argument is that children learn more at 7:15 a.m. than at 8:30. Instead, he forcefully reasons, schools are scheduled for adult convenience: there's no educational reason we start schools as early as we do. "If schools are for education, then we should promote learning instead of interfere with it," he challenges.
It's not just academics:
Several scholars have noted that many hallmark traits of modern adolescence--moodiness, impulsiveness, disengagement--are also symptoms of chronic sleep deprivation. Might our culture-wide perception of what it means to be a teenager be unwittingly skewed by the fact they don't get enough sleep?
But there's more:
All the studies point in the same direction: on average, children who sleep less are fatter than children who sleep more.
A big difference:
Among the middle schoolers and high schoolers studied, the odds of obesity went up 80% for each hour of lost sleep.
From Chapter Two: The Lost Hour in NurtureShock: New Thinking About Children by Po Bronson & Ashely Merryman