Journal of Environmental and Public Health / 2011 / Article / Tab 2

Research Article

Distance Traveled and Cross-State Commuting to Opioid Treatment Programs in the United States

Table 2

Multilevel model predicting patient travel distance to OTP.

Predictor95% Confidence interval
Zero-order correlationRegression coefficientSELowerEst.Upper

Block one
 USA Region
  Southeast versus Northeast 0.1451.3541.8082.413
  Midwest versus Northeast 0.1701.0151.4242.000
  West versus Northeast −0.215 0.1690.5760.8071.130
 Urbanicity
  250 K–1 M versus Metro >1 M 0.1291.0511.3591.758
  <250 K versus Metro >1 M 0.1601.2231.6832.316

Block two
 Patient ZIP code area 0.0061.3451.3601.375
 Program ZIP code area 0.036 0.0500.9381.0371.146

Block three
 Age
  30–43 versus 18–29 −0.021 0.0130.9540.9791.004
  43–81 versus 18–29 0.0160.8710.8990.927
 Female<.01 −0.019 0.0120.9580.9811.005
 Race/ethnicity
  Hispanic versus non-Hispanic white 0.0220.6800.7090.740
  Black versus non-Hispanic white 0.0250.6050.6350.666
  Other versus non-Hispanic white 0.0360.8360.8960.961
 Employed 0.005 0.0120.9720.9951.019

Block four
 Pain a reason for treatment.01 −0.011 0.0120.9650.9891.013
 First methadone treatment 0.0040.0120.9801.0041.028
 Strong urge to use <0.0010.0180.9661.0001.035
 Severe withdrawal 0.0030.0140.9761.0031.030
 Prescription opioid use in past 30 days 0.0161.0511.0851.119
 Heroin use in past 30 days −0.031 0.0170.9390.9701.002

Interval estimates for each predictor have been exponentiated and can be interpreted as how travel distance is multiplied given a one-unit change in the predictor (or a contrast between one level of a categorical predictor and the reference category for that predictor). For predictors with multiple categories (i.e., USA Region, Urbanicity, Age, and Race/Ethnicity), the zero-order correlation is the multiple correlation when log distance is regressed on dummy variables.
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