title: Tracking Adolescents With Global Positioning System-Enabled Cell Phones to Study Contextual Exposures and Alcohol and Marijuana Use: A Pilot Study.
abstract: OBJECTIVE
  Measuring activity spaces, places adolescents spend time, provides information about relations between contextual exposures and risk behaviors. We studied whether contextual exposures in adolescents' activity spaces differ from contextual risks present in residential contexts and examined relationships between contextual exposures in activity spaces and alcohol/marijuana use.
  
  
  METHODS
  Adolescents (N = 18) aged 16-17 years carried global positioning system (GPS)-enabled smartphones for 1 week, with locations tracked. Activity spaces were created by connecting global positioning system points sequentially and adding buffers. Contextual exposure data (e.g., alcohol outlets) were connected to routes. Adolescents completed texts regarding behaviors.
  
  
  RESULTS
  Adolescent activity spaces intersected 24.3 census tracts and contained nine times more alcohol outlets than that of residential census tracts. Outlet exposure in activity spaces was related to drinking. Low-socioeconomic status exposure was related to marijuana use.
  
  
  CONCLUSIONS
  Findings suggest substantial differences between activity spaces and residential contexts and suggest that activity spaces are relevant for adolescent risk behaviors.
authors.affiliation: Prevention Research Center, Pacific Institute for Research and Evaluation, Oakland, California. Electronic address: hbyrnes@prev.org.
authors.forename: Hilary F
authors.initials: HF
authors.lastname: Byrnes
authors.affiliation: Prevention Research Center, Pacific Institute for Research and Evaluation, Oakland, California.
authors.forename: Brenda A
authors.initials: BA
authors.lastname: Miller
authors.affiliation: Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Wiebe
authors.affiliation: Prevention Research Center, Pacific Institute for Research and Evaluation, Oakland, California; Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Morrison
authors.affiliation: Prevention Research Center, Pacific Institute for Research and Evaluation, Oakland, California.
authors.forename: Lillian G
authors.initials: LG
authors.lastname: Remer
authors.affiliation: Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana; Department of Public Health, Indiana University School of Medicine, Indianapolis, Indiana; Department of Geography, Indiana University Purdue University, Indianapolis, Indiana; Regenstrief Institute for Health Care, Indianapolis, Indiana.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Wiehe
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000428:Alcohol Drinking / Q000523:psychology*; D040421:Cell Phone; D005260:Female; D040362:Geographic Information Systems / Q000295:instrumentation* / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000523:psychology*; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012309:Risk-Taking
keywords: Activity space; Adolescent alcohol and risk behaviors; Contextual risk exposure; Global positioning system