By Bradley Schnierow, MD
This coming Sunday morning (Nov. 7), all of us stand to gain an extra hour of sleep as we “fall back” from Daylight Savings Time to Standard Time. While an extra hour of sleep is always welcomed (and encouraged by sleep physicians such as myself), it is a mere drop in the ocean for the majority of us who are chronically sleep deprived by the busy demands of modern life.
It may be surprising to learn that psychological studies have repeatedly shown that for optimal mental function (e.g., memory, reaction time, creative thinking) nine hours of sleep each night is ideal. Sadly, the average American logs just over seven hours on a typical night. Those who dismiss such studies as not applying to them because they get by on fewer than seven hours are in for some sobering news: These same studies have shown that after a few weeks of chronic sleep deprivation, people are likely to become unaware of their impairment. Ironically, sleep deprivation results in not knowing you’re sleep-deprived.
Although budgeting too little time for a night’s slumber affects all ages, teenagers are particularly likely to be short-changed. This is due to misalignment of their internal circadian clock with school start times.
In order to understand this mismatch and how to fix it, we first need to describe the evolutionary development of our internal circadian clock: Imagine our ancestors living long before the advent of artificial lighting. They would wake up with the morning sun and begin their day of hunting and gathering. At the start of the day their need for sleep would be at a minimum, but every hour they were awake the need for sleep would grow. By nightfall they would be pretty sleepy, and with the approaching darkness there was nothing in their environment to stimulate them to stay awake. But going to sleep at the first onset of night is dangerous; nocturnal animals are all leaving their lairs, and if someone is not paying attention he could become their next meal! It is at this point that the internal clock enters the picture. This collection of nerve cells resides in the primitive brain (hypothalamus), and signals to the developed brain (cortex) “Stay awake. Don’t get eaten.” This internal signal still affects each of us to this day. It is the increase in energy that most of us experience usually around dinnertime (the so-called “second wind”). The biological clock eventually shuts off for most of us between 9 to 11 p.m.
For unclear reasons, the biological clock becomes delayed at the start of adolescence. It is not a rebellious youthful attitude, but innate biology, that explains why 70 percent of teenagers often stay up past midnight and like to sleep their mornings away. Instead of getting a second wind at dinnertime, the delayed internal clock kicks in around 9 to 10 p.m. If an affected high school student goes to bed at that time, the result is often hours spent lying in bed with a mind that won’t “shut off.”