Sleep and screens are not good bedfellows, and young people who use their smartphones at bedtime are getting significantly worse and less sleep, according to new research by scientists in the US. In the study, people aged between 15 and 18 had their sleep monitored using fitness trackers. Participants also recorded their screen time, the number of notifications they received and when they looked at their mobile phones. One key finding was that if the teens had more screen time at night compared to their average, they fell asleep later and had poorer sleep. The same applied to frequently unlock…