Light displays disturb "sleepy" melatonin.

• Position: Insomnia

A two-hour exposure to electronic devices with self-luminous "backlit" displays causes melatonin suppression, which might lead to delayed bedtimes, especially in teens, maintains a study appearing in Applied Ergonomics.

A research team led by Mariana Figueiro, associate professor at Rensselaer Polytechnic Institute, Troy, N.Y., and director of its Lighting Research Center's Light and Health Program, tested the effects of self-luminous tablets on melatonin suppression. In order to simulate typical usage of these devices, individuals used self-luminous tablets to read, play games, and watch movies.

"Our study shows that a two-hour exposure to light from self-luminous electronic displays can suppress melatonin by about 22%," says Figueiro. "Stimulating the human circadian system to this level may affect sleep in those using the devices prior to bedtime."

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."

Manufacturers may want to design more "circadian-friendly" electronic devices that either could increase or decrease circadian stimulation depending on the time of day--reducing circadian stimulalton in the evening for a better night's sleep, and increasing it 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...