title: Validating self-reported mobile phone use in adults using a newly developed smartphone application.
abstract: OBJECTIVE
  Interpretation of epidemiological studies on health effects from mobile phone use is hindered by uncertainties in the exposure assessment. We used a newly developed smartphone application (app) to validate self-reported mobile phone use and behaviour among adults.
  
  
  METHODS
  107 participants (mean age 41.4 years) in the Netherlands either downloaded the software app on their smartphone or were provided with a study smartphone for 4 weeks. The app recorded the number and duration of calls, text messages, data transfer, laterality and hands-free use. Self-reported mobile phone use was collected before using the app and after 6 months through an interviewer-administered questionnaire.
  
  
  RESULTS
  The geometric mean ratios (GMR, 95% CI) and Spearman correlations (r) of self-reported (after 6 months) versus recorded number and duration of calls were: GMR=0.65 (0.53 to 0.80), r=0.53; and GMR=1.11 (0.86 to 1.42), r=0.57 respectively. Participants held the phone on average for 86% of the total call time near the head. Self-reported right side users held the phone for 70.7% of the total call time on the right side of the head, and left side users for 66.2% on the left side of the head. The percentage of total call time that the use of hands-free devices (headset, speaker mode, Bluetooth) was recorded increased with increasing frequency of reported hands-free device usage.
  
  
  CONCLUSIONS
  The observed recall errors and precision of reported laterality and hands-free use can be used to quantify and improve radiofrequency exposure models based on self-reported mobile phone use.
authors: Department of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors: Geertje
authors: http://orcid.org/0000-0002-7219-5316
authors: G
authors: Goedhart
authors: Department of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors: Hans
authors: H
authors: Kromhout
authors: Whist Lab, Institut Mines Telecom and Orange Labs, Paris, France.
authors: Joe
authors: J
authors: Wiart
authors: Department of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands School of Public Health, Imperial College London, London, UK.
authors: Roel
authors: http://orcid.org/0000-0003-4082-8163
authors: R
authors: Vermeulen
mesh_terms: D000328:Adult; D000368:Aged; D040421:Cell Phone / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D006225:Hand; D006257:Head; D006801:Humans; D008297:Male; D008875:Middle Aged; D063731:Mobile Applications / Q000592:standards*; D008962:Models, Theoretical; D009426:Netherlands; D011846:Radio Waves; D057566:Self Report; D000068997:Smartphone; D060145:Text Messaging