In October 2018 researchers from Denmark published the results of their study to assess whether there was any association between overnight smartphone use and associated interrupted sleep with mental and other health issues. A total of 815 young adults agreed to have their smartphone activity continuously monitored over a 4-week period. Results showed that over 12% used their smartphone in the middle of the night (3-5 hours after going to bed), with 41% experiencing interrupted sleep due to their smartphone on at least one day per week. Those with frequent interrupted sleep had, on average, 48 minutes less sleep. A further analysis revealed that those individuals with a shorter sleep duration also had a higher body mass index. There did not appear to be any association with mental or other health issues.
Rod NH et al. Overnight smartphone use: A new public health challenge? A novel study design based on high-resolution smartphone data. PLoS One. 2018 Oct 16;13(10):e0204811.