Light from Self Luminous Screens Hampers Sleep

Are you habituated to keeping yourself occupied with you iPad or cellphone before falling off asleep?  It may not be a good idea. The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute's study says that two hours exposures to the electronic devices with self luminous 'backlit' displays have the tendency to trigger melatonin suppression, causing havoc on your sleep.

In order to conduct the study, the researchers tested the effects of self-luminous tablets on melatonin suppression. In which 13 subjects used self-luminous tablets to read, play games, and watch movies.

Melatonin that is termed as the time messenger is produced by the pineal gland at night. When exposed to light in the night the melatonin gets suppressed resulting in circadian disruption.

"Our study shows that a two-hour exposure to light from self-luminous electronic displays can suppress melatonin by about 22 percent. Stimulating the human circadian system to this level may affect sleep in those using the devices prior to bedtime," said Mariana Figueiro, associate professor at Rensselaer and director of the LRC's Light and Health Program who is also the main researcher of the  team.

The actual melatonin suppression values after 60 minutes were very similar to those estimated using a predictive model of human circadian photo transduction 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.

This study that is carried in the journal Applied Ergonomics, urges the manufacturers to design more "circadian friendly" electronic devices that wither initiates or subsides circadian stimulation.

"Technology developments have led to bigger and brighter televisions, computer screens, and cell phones," said LRC Research Specialist Brittany Wood who used the study as the basis for her master's thesis. "To produce white light, these electronic devices must emit light at short wavelengths, which makes them potential sources for suppressing or delaying the onset of melatonin in the evening, reducing sleep duration and disrupting sleep. This is particularly worrisome in populations such as young adults and adolescents, who already tend to be night owls."  

The subjects were divided into three groups out of which the first one viewed their tablets through a pair of clear goggles fitted with 470-nm (blue) light from light emitting diodes (LEDs). This was referred to 'true positive condition'. The second group viewed their tablets through orange-tinted glasses, capable of filtering out the short-wavelength radiation that can suppress melatonin; this was the "dark control" condition. The third group did not wear glasses or goggles. All the subjects were asked to wear Dimesimeter, which is a small calibrated light meter device, close o their eye.

The researchers noticed that, "duration of exposure and the distance between the eye and the display, which determines the amount of light reaching the back of the eye, affects melatonin levels. Melatonin suppression after a one-hour exposure to the tablet was not significantly affected. However, after a two-hour exposure there was significant suppression."

Figueiro has several recommendations to reduce their effects on sleep. "We recommended dimming these devices at night as much as possible in order to minimize melatonin suppression, and limiting the amount of time spent using these devices prior to bedtime."