The number of people with sleep disorders is set to rise say experts because of the effect artificial light from tablets and laptops has on the body clock.According to leading Australian researcher Professor Shantha Rajaratnam, there is growing evidence to support the claim that the use of portable digital devices at night has a negative effect on people's sleep. He said that since electric lighting, the number of people suffering sleep disorders has risen steadily. Professor Rajaratnam predicted the number of sufferers will rise if people continue to use mobile devices at night.It comes after a study in the US reported that laptops, smartphones and tablets emit up to 50 lux, or around half the illumination of an ordinary room light.According to ABC News, having such a high level of light in your room at night will reduce the melatonin your body produces, as in order to produce the hormone, you need darkness. With reduced melatonin, people find it harder to fall asleep.Professor Rajaratnam suggested turning off devices at least one hour before bed.http://www.abc.net.au/news/2013-07-01/artificial-light-leading-to-increase-in-sleep-disorders/4790448