Exposure to morning short-wavelength “blue” light may help sleep-deprived teens prepare for any stress or challenges that might come that day, more than dim light exposure.
Fixed wake up times on school days, as well as not being able to fall asleep early, are causing many adolescents to become chronically sleep deprived. The CDC reports that nearly 70% of school kids are not getting the appropriate amount of sleep. Studies show that they are resting for less than 8 hours on week days.
Previous research has associated insufficient sleep with depression, drug use, and automobile accidents. A study in the journal SLEEP suggested that kids just who get do not get enough sleep at night are more likely to have behavioral and cognitive problems at school.
The current research, published in International Journal of Endocrinology and conducted at Rensselaer Polytechnic Institute, set out to examine the effects of short-wavelength light on the cortisol awakening response.
Levels of cortisol, a hormone produced by the adrenal gland, follow a routine pattern every day. Concentrations of this hormone are low during the day, and then arrive at the lowest levels at nightfall, eventually increasing again throughout the night. Cortisol levels also dramatically increase within the hour after a person wakes up.
This process is referred to as CAR (cortisol awakening response). Nocturnal animals experience this “cortisol spike” at night when they wake up. Scientists believe it is related to the time of change from rest to activity. A high CAR has been linked with better readiness for stressful and challenging events.
Mariana Figueiro, Associate Professor and Director of the LRC (Lighting Research Center) Light and Health Program, explained:
“The present results are the first to show that low levels of short-wavelength light enhance CAR in adolescents who were restricted from sleep. Morning light exposure may help to wake up the body when it is time to be active, thus preparing individuals for any environmental stress they might experience.”
Experts have indicated that short-wavelength light can phase shift the schedule of the biological clock and best prevent production of nocturnal melatonin. However, there is not much research on its influence on other biomarkers.
For the purpose of this study, subjects, aged 12 to 17, were analyzed during three overnight stays, which took place at least one week apart. They were able to sleep for four and a half hours, from 1:30 a.m. until 6:00 a.m. Each week, the volunteers were either exposed to morning short-wavelength blue light (40 lux of 470-nanometer light) or they experienced dim light.
A Dimesimeter on a wrist band was worn by each person, so that the experts could observe light exposure, while also test the regularity of their activity and rest times. The LRC developed this instrument, which is a small calibrated light meter that constantly records activity levels and circadian light.
Professor and LRC Director Mark S. Rea concluded:
“We found that exposure to short-wavelength blue light in the morning significantly enhances CAR in sleep deprived adolescents, more so than dim light,” said Rea. “Morning exposure to short-wavelength light may be a simple, yet practical way to better prepare adolescents for the challenges of the day.”
Written by, Sarah Glynn.