A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that a two-hour exposure to electronic devices with self-luminous “backlit” displays causes melatonin suppression, which might lead to delayed bedtimes, especially in teens.
 
The research team, led by Mariana Figueiro, associate professor at Rensselaer and director of the LRC’s Light and Health Program, tested the effects of self-luminous tablets on melatonin suppression. In order to simulate typical usage of these devices, 13 individuals used self-luminous tablets to read, play games, and watch movies. Results of the study, titled “Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression,” were recently published in the journal Applied Ergonomics.
 
“Our study shows that a two-hour exposure to light from self-luminous electronic displays can suppress melatonin by about 22%. Stimulating the human circadian system to this level may affect sleep in those using the devices prior to bedtime,” said Figueiro.
 
The actual melatonin suppression values after 60 minutes were very similar to those estimated using a predictive model of human circadian phototransduction for one-hour light exposures. “Based on these results, display manufacturers can use our model to determine how their products could affect circadian system regulation,” said Figueiro.
 
The results of this study, together with the LRC predictive model of human circadian phototransduction, could urge manufacturers to design more “circadian-friendly” electronic devices that could either increase or decrease circadian stimulation depending on the time of day—reducing circadian stimulation in the evening for a better night’s sleep, and increasing in the morning to encourage alertness. In the future, manufacturers might be able to use data and predictive models to design tablets for tailored daytime light exposures that minimize symptoms of seasonal affective disorder, and sleep disorders in seniors. Individuals would be able to receive light treatments while playing games or watching movies, making light therapy much more enjoyable than just sitting in front of a light box.   
 
Along with Figueiro, co-authors of the study are LRC Director and Professor Mark S. Rea, LRC Research Specialist Brittany Wood, and LRC Research Nurse Barbara Plitnick.
 
Melatonin is a hormone produced by the pineal gland at night and under conditions of darkness in both diurnal and nocturnal species. It is a “timing messenger,” signaling nighttime information throughout the body. Exposure to light at night, especially short-wavelength light, can slow or even cease nocturnal melatonin production. Suppression of melatonin by light at night resulting in circadian disruption has been implicated in sleep disturbances, increased risk for diabetes and obesity, as well as increased risk for more serious diseases, such as breast cancer, if circadian disruption occurs for many consecutive years, such as in nightshift workers.