Waking Up Teens - Scientists Show Blue Light Can Help Reset Sleep Cycle

February 1, 2006 — Teenagers' morning drowsiness is often caused by out-of-tune body clocks, in a condition known as "delayed sleep phase syndrome." Scientists now say that timing exposure to blue light -- avoiding it during the first two hours of being wake, then getting a good dose of it -- can help restore the sleep cycle, so teens feel sleepy earlier at night and are more awake in the morning.

TROY, N.Y.--Teenagers are notorious for staying up late, hitting the snooze button and always running late. Now, however, new research shows they can adjust to a schedule simply by sitting in front of a light.

Erin Chesky knows just how hard it is to get up because she battled getting to sleep. "I would just stare at the ceiling, and then I would have to wake up at 5:30 or 5 o'clock to go to school, and I would be tired," she says.

The 16-year-old was diagnosed with delayed sleep phase syndrome. That means Erin's internal clock didn't match what was her alarm clock was saying.

Mariana Figueiro, from the Lighting Research Center at the Rensselaer Polytechnic Institute in Troy, N.Y., says, "When your watch says it's 7 o'clock in the morning, you want your internal clock to also say it is 7 o'clock in the morning."

Lighting scientists have found a quick fix to the internal and external alarm clock miscommunication -- a blue light. "If you apply the light after your minimum core body temperature, you're going to advance the clock so you're going to go to bed earlier and wake up earlier the next cycle," Figueiro says. The minimum core body temperature is reached about two hours before a person naturally wakes up.

"When you get the teenager up, outdoors, waiting for the school bus at 7 o'clock in the morning, they may be getting light at the wrong phase," Figueiro says. This exposes teens to natural blue light too early. By wearing the goggles when teens wake up, blue light is blocked out. Then, later in the morning -- after their minimum core body temperature is reached -- teens can reset their internal clocks by being out in the light.

Blue light exposure worked quickly for Erin. She's now able to fall asleep by 10:30.

An easy way schools can help is by giving students a quick mid-morning break to go outside or put blue LEDs around computer screens in classrooms. By getting enough blue light at the right time, sleep patterns can not only be changed in teens, but also in the elderly and shift workers.

BACKGROUND: Researchers at Rensselaer Polytechnic Institute are studying how light -- especially blue light -- affects our body's daily rhythms. By getting enough blue light at the right time and blocking it out at others, it is possible to correct distorted sleep patters for the elderly (who tend to wake up too early), teenagers (whose internal clock is usually set for late nights and sleep-in mornings), and shift workers.

HOW BODY RYHTHMS WORK: Circadian rhythms are biological cycles in the body that repeat approximately every 24 hours, including the sleep/wake cycle, along with body temperature, hormone levels, heart rate, blood pressure, and pain threshold. The brain has its own internal "pacemaker" that determines when nerve cells fire to set the body's rhythms, although scientists can't precisely explain how it does so.

The colors of the light spectrum can affect the body's rhythm differently, particularly when it comes to sleep patterns. For instance, daylight is dominated by short, visible wavelengths of light that provides a blue visual sensation, like the blue sky. But l how bright the light is, how far away, how long you're exposed and when you're exposed to light also have to be considered. Also, we are more likely to sleep soundly in the wee hours of the morning, when our body temperature is lowest, and most likely to awaken when our body temperature starts to rise, usually between 6 AM and 8 AM. As we age, the brain's "pacemaker" loses cells, changing circadian rhythms, especially sleep patterns. The elderly may nap more frequently, have disrupted sleep, or awaken earlier.

RESETTING THE CLOCK: The RPI researchers developed a method for resetting the internal "master clock" in studies of both teens and the elderly. The scheme removes blue light at certain times (depending on how one wants to "reset the clock") by wearing orange glasses, followed by exposure to blue light and darkness at nighttime. The key is a distinct, repeated pattern of light and dark.

SLEEP STAGES: Stage 1: drowsiness. Stage 2: light sleep. Stages 3 and 4: deep sleep. Stage 5: Rapid-eye movement (REM) sleep. REM is when people dream, perhaps because the brain is more active and the muscles are relaxed. These five stages occur cyclically; a person may complete five cycles in a typical night's sleep.

Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.

Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.