title: Bedtime mobile phone use and sleep in adults.
abstract: BACKGROUND
  The few studies that have investigated the relationship between mobile phone use and sleep have mainly been conducted among children and adolescents. In adults, very little is known about mobile phone usage in bed our after lights out. This cross-sectional study set out to examine the association between bedtime mobile phone use and sleep among adults.
  
  
  METHODS
  A sample of 844 Flemish adults (18-94 years old) participated in a survey about electronic media use and sleep habits. Self-reported sleep quality, daytime fatigue and insomnia were measured using the Pittsburgh Sleep Quality Index (PSQI), the Fatigue Assessment Scale (FAS) and the Bergen Insomnia Scale (BIS), respectively. Data were analyzed using hierarchical and multinomial regression analyses.
  
  
  RESULTS
  Half of the respondents owned a smartphone, and six out of ten took their mobile phone with them to the bedroom. Sending/receiving text messages and/or phone calls after lights out significantly predicted respondents' scores on the PSQI, particularly longer sleep latency, worse sleep efficiency, more sleep disturbance and more daytime dysfunction. Bedtime mobile phone use predicted respondents' later self-reported rise time, higher insomnia score and increased fatigue. Age significantly moderated the relationship between bedtime mobile phone use and fatigue, rise time, and sleep duration. An increase in bedtime mobile phone use was associated with more fatigue and later rise times among younger respondents (≤ 41.5 years old and ≤ 40.8 years old respectively); but it was related to an earlier rise time and shorter sleep duration among older respondents (≥ 60.15 years old and ≥ 66.4 years old respectively).
  
  
  CONCLUSIONS
  Findings suggest that bedtime mobile phone use is negatively related to sleep outcomes in adults, too. It warrants continued scholarly attention as the functionalities of mobile phones evolve rapidly and exponentially.
authors.affiliation: School for Mass Communication Research, KU Leuven, Parkstraat 45, 3000 Leuven, Belgium. Electronic address: liese.exelmans@soc.kuleuven.be.
authors.forename: Liese
authors.initials: L
authors.lastname: Exelmans
authors.affiliation: School for Mass Communication Research, KU Leuven, Parkstraat 45, 3000 Leuven, Belgium. Electronic address: jan.vandenbulck@soc.kuleuven.be.
authors.forename: Jan
authors.initials: J
authors.lastname: Van den Bulck
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001530:Belgium / Q000453:epidemiology; D040421:Cell Phone / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D005221:Fatigue / Q000453:epidemiology*; D006801:Humans; D008875:Middle Aged; D057566:Self Report; D012890:Sleep; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology*; D013997:Time Factors; D055815:Young Adult
keywords: Adults; Age; Belgium; Fatigue; Insomnia; Mobile phone; PSQI; Sleep