Lighting Research Center
LRC Intranet Web mail Lighting Research Center
 

Press Releases


 


Back To Press Releases

For Immediate Release

Contact:   Rebekah Mullaney
Lighting Research Center
518.687.7118
mullar2@rpi.edu
  Newsroom Home
  Project Sheets
  In the News
  LRC Experts
  About Us
  Contact Us
Troy, N.Y. -  10/22/2012

"Blue" Light Could Help Teenagers Combat Stress

Short-Wavelength Light Increases Beneficial Stress Hormone Response in Sleep-Restricted Adolescents

 Adolescents can be chronically sleep deprived because of their inability to fall asleep early in combination with fixed wakeup times on school days. According to the Centers for Disease Control (CDC), almost 70 percent of school children get insufficient sleep—less than 8 hours on school nights. This type of restricted sleep schedule has been linked with depression, behavior problems, poor performance at school, drug use, and automobile accidents. A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that exposure to morning short-wavelength “blue” light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

The study was a collaboration between Associate Professor and Director of the LRC Light and Health Program Mariana Figueiro and LRC Director and Professor Mark S. Rea. Results of the study titled “Short-Wavelength Light Enhances Cortisol Awakening Response in Sleep-Restricted Adolescents,” were recently published in the open access International Journal of Endocrinology. The full text is available at http://www.hindawi.com/journals/ije/2012/301935/.

Levels of cortisol, a hormone produced by the adrenal gland, follow a daily 24-hour rhythm. Cortisol concentrations are low throughout the day reaching a broad minimum in the evening before rising slowly again throughout the night. In addition to this gradual elevation of cortisol at night, cortisol levels rise sharply within the first 30 to 60 minutes after waking. This is known as the cortisol awakening response (CAR). In nocturnal animals, the cortisol spike occurs at night, at the start of activity. It appears to be associated with the time of transition from rest to activity, upon waking. A high CAR has been associated with better preparedness for stressful and challenging activities.

“The present results are the first to show that low levels of short-wavelength light enhance CAR in adolescents who were restricted from sleep,” said Figueiro. “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.”

Short-wavelength light has been shown to maximally suppress production of nocturnal melatonin and phase shift the timing of the biological clock. The effect of short-wavelength light on other biomarkers has not been widely studied.

The study included three overnight sessions, at least one week apart. All participants wore a Dimesimeter on a wrist band to measure light exposure and to verify the regularity of their activity/rest periods during the three-week study. The Dimesimeter is a small calibrated light meter device developed by the LRC that continuously records circadian light and activity levels. During the study, adolescents aged 12 to 17 years went to sleep at 1:30 a.m. and woke up at 6:00 a.m., a 4.5-hour sleep opportunity. Each week, participants either experienced morning short-wavelength blue light (40 lux of 470-nanometer light) or remained in dim light.

“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.”

How can teenagers get morning exposure to blue light? According to Figueiro and Rea, light exposure needs to occur within one hour of waking to have an impact on CAR. Blue light is available in daylight, but in winter, it is often dark when teens are waking up for school, due to later sunrise. More consistent options include blue light goggles and light boxes. Backlit tablets and computer screens provide blue light, but further research is needed to accurately measure how much light is produced by each product. Compared with light goggles or a light box, backlit tablets and computer screens provide a weaker light, and therefore would need to be used for a longer period of time to get the same effect. 

The study was funded by Sharp Laboratories of America.


About the Lighting Research Center
The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute is the world's leading center for lighting research and education. Established in 1988 by the New York State Energy Research and Development Authority (NYSERDA), the LRC has been pioneering research in energy and the environment, light and health, transportation lighting and safety, and solid-state lighting for more than 25 years.
In 1990, the LRC became the first university research center to offer graduate degrees in lighting and today the LRC offers both a M.S. in lighting as well as a Ph.D. to educate future leaders in lighting. Internationally recognized as the preeminent source for objective information on all aspects of lighting technology and application, LRC researchers conduct independent, third-party testing of lighting products in the LRC's state of the art photometric laboratories, the only university lighting laboratories accredited by the National Voluntary Laboratory Accreditation Program (NVLAP Lab Code: 200480-0). LRC researchers are continuously working to develop new and better ways to measure the value of light and lighting systems, such as the effect of light on human health, and the effect of light on plant physiology.
The LRC believes that by accurately matching the lighting technology and application to the needs of the end user, it is possible to design lighting that benefits both society and the environment.

About Rensselaer Polytechnic Institute
Rensselaer Polytechnic Institute, founded in 1824, is the nation's oldest technological university. The university offers bachelor's, master's, and doctoral degrees in engineering, the sciences, information technology, architecture, management, and the humanities and social sciences. Institute programs serve undergraduates, graduate students, and working professionals around the world. Rensselaer faculty are known for pre-eminence in research conducted in a wide range of fields, with particular emphasis in biotechnology, nanotechnology, information technology, and the media arts and technology. The Institute is well known for its success in the transfer of technology from the laboratory to the marketplace so that new discoveries and inventions benefit human life, protect the environment, and strengthen economic development.