In this 2014 study, Prof Richard Wiseman of the University of Hertfordshire conducted an online study into the sleeping habits of 2,149 adults indicating a 50% rise in the number of sleep-deprived Britons. He found that 59% of respondents were now sleep-deprived in contrast to just 39% the previous year. Sleep-deprivation was defined as having less than seven hours sleep. 78% of people admitted to using a smartphone in the two hours before bedtime as opposed to 57% the previous year. Among 18-24 year-olds that figure rose to 91%.
Mobile phones, tablets and computers emit blue light, which is present in morning light. This tricks the body into thinking that it is time to wake up, speeding up the metabolism and making sleep more difficult. It suppresses the production of the sleep-inducing hormone melatonin. Sleeping for seven hours or less is thought to increase the risk of cancer, diabetes and heart attacks as well as disrupting cognitive and emotional functioning.
It is recommended that affected individuals avoid using computers, smartphones or tablets for two hours before going to bed.http://www.herts.ac.uk/about-us/news/2014/april/online-survey-reveals-new-epidemic-of-sleeplessness