title: Modeling time-location patterns of inner-city high school students in New York and Los Angeles using a longitudinal approach with generalized estimating equations.
abstract: The TEACH Project obtained subjects' time-location information as part of its assessment of personal exposures to air toxics for high school students in two major urban areas. This report uses a longitudinal modeling approach to characterize the association between demographic and temporal predictors and the subjects' time-location behavior for three microenvironments--indoor-home, indoor-school, and outdoors. Such a longitudinal approach has not, to the knowledge of the authors, been previously applied to time-location data. Subjects were 14- to 19-year-old, self reported non-smokers, and were recruited from high schools in New York, NY (31 subjects: nine male, 22 female) and Los Angeles, CA (31 subjects: eight male, 23 female). Subjects reported their time-location in structured 24-h diaries with 15-min intervals for three consecutive weekdays in each of winter and summer-fall seasons in New York and Los Angeles during 1999-2000. The data set contained 15,009 observations. A longitudinal logistic regression model was run for each microenvironment where the binary outcome indicated the subject's presence in a microenvironment during a 15-min period. The generalized estimating equation (GEE) technique with alternating logistic regressions was used to account for the correlation of observations within each subject. The multivariate models revealed complex time-location patterns, with subjects predominantly in the indoor-home microenvironment, but also with a clear influence of the school schedule. The models also found that a subject's presence in a particular microenvironment may be significantly positively correlated for as long as 45 min before the current observation. Demographic variables were also predictive of time-location behavior: for the indoor-home microenvironment, having an after school job (OR=0.67 [95% confidence interval: 0.54:0.85]); for indoor-school, living in New York (0.42 [0.29:0.59]); and for outdoor, being 16-year-old (0.80 [0.67:0.96]), 17-year-old (0.71 [0.54:0.92]), and having an after school job (1.29 [1.07:1.56]).
authors.affiliation: Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. decastro@jhu.edu
authors.forename: B Rey
authors.initials: BR
authors.lastname: Decastro
authors.forename: Sonja N
authors.initials: SN
authors.lastname: Sax
authors.forename: Steven N
authors.initials: SN
authors.lastname: Chillrud
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Kinney
authors.forename: John D
authors.initials: JD
authors.lastname: Spengler
mesh_terms: D000293:Adolescent; D000328:Adult; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D005260:Female; D006798:Housing; D006801:Humans; D016015:Logistic Models; D015141:Los Angeles; D008297:Male; D015999:Multivariate Analysis; D009519:New York City; D012574:Schools; D013334:Students; D013997:Time Factors; D014505:Urban Population