It may not seem obvious, but in our daily round of activities, sleep must be counted among the most important. Recent reports have shown that teens in North America are sleep deprived, averaging less than seven hours per sleep per night when they require almost nine hours. Surely, cell phones, computers, online gaming, and television are part of the cause for this; but it would be too simple to say that teens don't sleep because they are absorbed by a more engaging activity.
In normal, healthy people, sleep is regulated or influenced by internal clocks, or circadian rhythms. The most germane of those rhythms that influence sleep is known as the rest-activity cycle. This cycle is influenced by hormones that are triggered by daylight, and a tiny gland in the skull known as the pineal gland has been implicated in explaining this. Humans evolved to be able to sleep during dark and be active during the day. Why? Because evolution works to maximize survival of species. Since humans see poorly in the dark, we are better off sleeping and being active during the daytime.
There is much to learn about sleep and how it serves to keep people healthy and mentally alert. We do know that it is vitally necessary to sleep. Extreme sleep deprivation can lead to death. We also know that normal sleep involves stages, and that the fourth stage, or Rapid Eye Movement (REM) stage of sleep, is thought to be the most important for its restorative properties. REM sleep is that stage of sleep during which we dream. If we don't achieve REM sleep, our sleep is of lesser quality. Normal humans go through several cycles involving all stages of sleep each night. People who sleep and say don't dream are simply not recalling their dreams.
Getting a good night's sleep (full of dreams) involves many factors. The most important factor for good sleep hygiene is having a rest-activity cycle that is entrained, or synchronized with what is happening in the social world. People need regular routines and activities to keep their internal clocks synchronized with the world. Jet lag after long distance air travel is a condition that places our internal clocks at odds with the social world around us when we fly to a new environment. Ordinarily, it can take as long as 30 days for the body to fully recover from jet lag.
Of course, shift workers are also at risk of insomnia caused by disentrainment, since shift workers must be active at night when their body tells them they should be sleeping. Of course, some adjustment does occur, as long as the shifts do not vary frequently. Some countries have laws that regulate shiftwork as a public health safeguard for such workers.
So, let's return to the issue of teens and sleep deprivation. It is likely that at least some of the sleep debt being accumulated by teens has less to do with the effects of more and more distracting late night activity than it does on the effects of such shiftwork on the internal clocks of the teens. It is likely that, like shift workers, teens' internal clocks have changed so that their rest-activity cycles have adjusted, so their body tells them they need to sleep until noon; while their parents and schools are telling them to get up at seven to begin classes or catch the bus! Thus it seems, their sleep deprivation is less about distracting activities, than it is about modified internal clocks.
