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Many teens have trouble waking up in the morning for school, and their circadian clock may be to blame. Researchers at Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) believe some teenagers who experience difficulty waking up in the morning may actually be suffering from sleep deprivation because their “internal” clock conflicts with the schedule they keep.

The LRC has worked extensively on the effects of light and health, particularly the effects of light on the body's circadian rhythms, biological cycles in the body that repeat approximately every 24 hours, including the sleep/wake cycle.

“Many teens are physically unable to fall asleep until late at night, yet they have to wake very early for school,” says Mariana Figueiro, Ph.D., light and health program director at the LRC. “This can lead to sleep deprivation, which can compromise the endocrine and immune system, as well as negatively impact other health and safety factors.”

The LRC research group believes that a form of light treatment could help alleviate sleep deprivation in teens by readjusting their internal clock.

Setting the internal clock
Circadian rhythms are synchronized by the 24-hour light/dark cycle, and exposure to light and dark stimuli help to set the body’s internal ‘master clock’ to match the solar day.

Light stimulus travels through the retina, the light-sensitive nerve tissue lining the back wall of the eye, to reach the master clock in the brain. There needs to be a distinct, repeated pattern of light and dark to tell the circadian system the solar time. By using a simple light regimen, we can “advance” or “delay” our internal clock, depending on our individual needs, according to Dr. Figueiro.

Daylight is a mixture of wavelengths dominated by short, visible wavelength light that, in isolation, gives a blue visual sensation, like the blue sky. In fact, blue light is most effective and efficient at stimulating the circadian system, according to Dr. Figueiro. However, she explains that it isn’t just the color that is important, but rather the entire 24-hour pattern of light intensity, spatial distribution, timing, and duration, all in combination with the color.

Light treatment for teens
If teens experience trouble waking up for school, then they may need to advance their internal clock so that they can fall asleep earlier at night. To do this they need to expose themselves to daylight or blue light soon after they naturally wake up and after they have reached their minimum core body temperature—minimum core body temperature typically occurs about one and a half hours before a person naturally awakes.

However, this can be a problem because some teenagers leave for school very early in the morning either before daybreak or before they have reached their minimum core body temperature. This may result in a delay in falling asleep at night.

LRC researchers are exploring ways to combat this problem, including the development of a light scheme that removes blue light in the morning before the teenager has reached minimum core body temperature. The idea is to use orange glasses in the early hours of the morning to block blue light. Then expose the teen to blue light later in the morning inside the classroom after the teen has reached minimum core body temperature but is unable to be exposed to daylight.