Is your smartphone ruining your sleep?
5 April 2014 Last updated at 09:55 BST
New technology such as smartphones and tablets could be affecting how much sleep people get, a survey suggests.
More than three quarters of those surveyed use devices with screens before going to sleep. The blue light they emit disrupts the body's natural processes.
Professor Richard Wiseman, a psychologist at the University of Hertfordshire who was behind the survey, says six out of ten people are now getting less than seven hours sleep a night.