Light Treatment May Help Regulate Teens' Sleep

NEW YORK (Reuters Health) - A simple treatment involving wearing orange glasses to block blue light may help reset teens' internal clocks so that they have less trouble waking for school in the morning and falling asleep at night, researchers say.

Sleep problems experienced by teens, who stay up late and then need to get up to leave for school in the early morning, may be due to a conflict between their internal clock and the normal 24-hour solar day.

As human beings, our internal clock runs slightly longer than 24 hours, Dr. Mariana Figueiro, of Rensselaer Polytechnic Institute's Lighting Research Center, in Troy, New York, told Reuters Health. For this reason, we need to reset our internal clocks -- advance them, so to speak -- to synchronize them to the light and dark cycles of the solar day. This resetting occurs when we sleep until our bodies wake naturally, about one and a half hours after reaching our core body temperature, and then expose ourselves to daylight.

Yet, some teens' may not reach their normal minimum core temperature until as late as 9AM, when they are sitting in a classroom, without the opportunity for exposure to daylight, according to Figueiro, the light and health program director at the center.

Exposing the circadian system to daylight at an earlier hour, as is the case when teens awake via an alarm clock and leave for school before reaching their core temperature, may interfere with the body's normal adjustment of the internal clock. What's more, the lack of daylight at the later morning hour, when the body needs it, "confuses" the circadian system even further, the researcher said.

Why teenagers may not reach their core temperature until later morning hours may be partly due to their melatonin levels. Normally, the body begins producing this hormone anywhere from 8PM to 11PM, so that the body's system can slow down.

Figueiro has observed, however, that some teens' melatonin levels at 1AM are similar to melatonin levels usually experienced during daylight hours. These teens' "internal daytime is extended throughout nighttime," so they naturally fall asleep later and consequently have problems waking in the early morning, she explained.

This is a "serious problem," Figueiro said, but there is a "very simple solution."

Figueiro and her colleagues propose that teenagers use orange glasses -- similar to the safety glasses worn by electrical workers -- to block daylight when they leave for school, thereby keeping their circadian system in darkness until their bodies catch up.

When their bodies reach that minimum core temperature, a few hours later, the teens should then be exposed to daylight -- Figueiro suggests a half hour outdoor school break at 10AM -- or exposure to artificial blue light so that the circadian system can adjust itself. (The wavelengths of daylight are visually interpreted as blue light, such as the blue sky.)

This light treatment, on a different schedule, may also be useful for older adults with the opposite problem -- a need to go to bed later and sleep later, Figueiro said.