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.”
Ironically, high school starts earlier than other grades, placing school district policy at odds with biology. From time to time school districts around the country have woken up to this reality and have delayed high school start times by up to two hours. The results have been universally positive: better academic performance, less tardiness, and fewer traffic accidents. The good news is, we don’t have to petition the school board to help students in our own community. Instead, we can just reset their biological clocks to go off at the preferred earlier time. This can be quickly accomplished by getting exposure to bright light prior to 8 a.m.
The best source of bright light is direct sunlight on a clear morning for 20 minutes. Exposure to an artificial light source for 30 minutes is an adequate substitute when the weather is overcast or students don’t have the opportunity to be outdoors in direct sun. Artificial lights are available without a prescription. They come in two forms: broad spectrum (white) fluorescent bulbs that are 10,000 lux in brightness, or the more compact and economical blue L.E.D. lights manufactured under the name GoLite.
Regardless of what type of light is used, it is essential that the start time of the exposure be correct. For the demands of school start times, exposure should generally be between 6 and 8 a.m. If the exposure is too late, or too early, it will be ineffective in changing the internal clock.
When a dose of morning light is effective the results are realized that very night. Instead of giving a boost of energy near bedtime, the biological clock shuts off and sleep comes easily. Because this advice sounds too simple to be true, my patients are often skeptical that it will work for them. The advice I give them is to try it and then tell me it didn’t work. Fortunately, it is very rare for anyone with a delayed clock to not enjoy the benefits of morning bright light.
A delayed clock often advances back after age 30. Some people are born with this delay (“night owls”) and carry it with them their entire lives. For all of these individuals, morning bright light is effective for advancing their phase when the demands of life require it.
Bradley Schnierow, MD, is a sleep medicine specialist with Scripps Memorial Hospital La Jolla. “To Your Health” is brought to you by the physicians and staff of Scripps La Jolla. For more information or to make an appointment, please call 1-800-SCRIPPS.