JOIN US 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, researchers say.
The new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute 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.
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,” Figueiro said.
“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,” Figueiro said.
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.