The exploding popularity of hand-held digital devices could lead to a big jump in sleep disorders, with experts warning the light emitted from digital screens can have a disturbing effect on the body clock.
Leading Australian researcher Professor Shantha Rajaratnam says there is growing evidence that the night time use of portable digital devices is likely to compound the problems associated with artificial lighting.
"We think that the advent of electric lighting has significantly impacted upon sleep-wake patterns, but with the proliferation of electronic devices that emit light we are expecting that these problems will increase," said Professor Rajatnam, from Monash University's School of Psychology and Psychiatry.
A recent study in the United States showed that devices such as laptops, smart phones and tablets emit approximately 30 to 50 lux, about half the illumination of an ordinary room light.
"We know from preliminary reports that this level of light emission, 30 to 50 lux, is sufficient over a week or so to delay the timing of the circadian clock as well as suppress the production of the hormone melatonin," says Professor Rajaratnam.
Body clock is affected by artificial light.
Short wavelength blue light is the most disruptive.
Body does not produce as much melatonin, a hormone that helps sleep.
Lack of sleep can affect alertness, concentration and memory.
Risk is most significant for adolescents.
Melatonin, which is produced when it is dark, helps regulate and promote sleep. People who do not have enough of the hormone take longer to fall asleep.
"The extent of the response of the circadian clock will depend on how bright the light is - that is how far away the device is from the eyes - as well as what colours of light are being emitted," Professor Rajaratnam said.
Most disruptive to the body clock is short wavelength blue light - exactly what backlit portable screens shine directly into the eyes.
In addition, the devices are held close to the face and they are easily used in bed.
Dimming the screen brightness may help reduce the effect and technology is being developed that will allow filtering of the worst wavelengths.
Professor Rajaratnam says the best solution is the simplest ( via abc.net.au ).
"We would recommend that these devices are shut down or closed off up to two hours before bed time, but at least one hour before bed time, to try to reduce the impact of these light sources on sleep."