London - Nine out of 10 children are not getting enough sleep or exercise and spend too much time at screens, experts warn.
Children who spend hours on smartphones and tablets move around less, and the blue light from the devices disrupts their sleeping patterns.
The study, by Loughborough University and University College London, looked at screen time, sleep and physical activity in children based on the Millennium Cohort Study of 2015 and 2016.
The study, in journal JAMA Pediatrics, states only 9.7% of 14 year olds in the UK meet three recommendations, with more than three-quarters of teenagers spending more than two hours on screens daily.
England has no screen time guidelines, but in Canada less than two hours a day is recommended for younger children.