Excessive use of smartphones and tablets may be keeping teens awake a night, according to a study that found adolescents who spend more than two hours a day with their gadgets are more likely to be sleep deprived. Most sleep experts agree that adolescents need nine hours of sleep each night to be engaged and productive students; less than seven hours is considered to be insufficient sleep. Researchers, including those from San Diego State University in the US, examined data from two surveys of more than 360,000 teenagers.
One survey asked students in the eighth, 10th and 12th grades how frequently they got at least seven hours of sleep, while the second survey asked ninth-12th-grade students how many hours of sleep they got on an average school night. Combining and analyzing data from both surveys, researchers found that about 40 percent of adolescents in 2015 slept less than seven…
