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Table 1 Participant baseline a characteristics, exposures and potentially confounding variables used in the analysis

From: Traffic-related air pollution and obesity formation in children: a longitudinal, multilevel analysis

Participant characteristics No. (%) Mean (SD)
Race/Ethnicity     
  African American 122 (2.68)   
  Asian 145 (3.19)   
  Hispanic 2462 (54.11)   
  Non-Hispanic White 1664 (32.18)   
  Other 357 (7.85)   
Gender     
  Male 2297 (50.51)   
  Female 2251 (49.49)   
Individual and household characteristics     
Parental Education     
  Less than High School 905 (21.75)   
  High School 781 (18.77)   
  Above High School 2575 (59.48)   
Second hand smoke     
  No one ever smoked in the house 3962 (97.22)   
  Anyone ever smoked in the house 309 (7.23)   
Ever Asthma     
  No 3501 (86.13)   
  Yes 564 (13.87)   
Spanish Speaker     
  No 3417 (75.1)   
  Yes 1133 (24.9)   
Local home or school environment     
  Having no food stores within 500 m road network buffer     
  No 1980 (48.09)   
  Yes 2137 (51.91)   
Street connectivity     
  (Gamma index 500 m buffer) 4117   0.4 0.06
Parks and recreation     
  (unit: acre in 500 m buffer) 3968   4.95 10.6
NDVI green coverb (in 500 m buffer) 4117   0.09 0.10
Recreation programs within 5 km 4117   29.7 34.20
Community social context     
Proportion of unemployed males and females    0.076 0.02
Community level violent crime rate     
  (Crimes per 100,000 population) 4550   511.73 268.04
Air pollution and traffic     
Total NOX (parts per billion) 4464   49.24 104.93
Traffic density within 150 m of the home 4464   19.49 18.82
Primary outcome     
BMI at baseline 4550   16.79 2.81
  Males 2297   16.87 2.81
  Females 2251   16.70 2.80
BMI at the end of follow up 4550   19.35 4.21
  Males 2297   19.50 4.36
  Females 2251   19.19 4.15
BMI CDC percentile at baseline     
  85 > BMIp 3201 (70.35)   
  85 ≤ BMIp < 95 660 (14.41)   
  95 ≤ BMIp 684 (15.03)   
  1. aFirst observation of the subjects in the first year of the study is N = 4550 with restriction of non-missing BMI and with two or more observations; numbers of subjects in the table vary due to missing covariate values.
  2. bNormalized difference vegetation index derived from Landsat satellite images.