Light from self-luminous tablet computers can affect evening melatonin, delaying sleep

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 per cent. 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 minimise 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.