Table 3: Multilevel logistic regression model predicting patient travel across state to OTP. 95% Conﬁdence interval of the unadjusted odds ratio 95% Conﬁdence interval of the adjusted odds ratio Lower Odds ratio Upper Lower Odds ratio Upper 0.314 1.044 0.003 1.649 0.105 0.921 1.024 0.943 0.891 0.872 0.262 0.198 0.196 0.778 0.882 0.722 0.667 0.778 0.654 0.854 2.516 11.826 0.063 10.959 1.384 0.983 2.007 1.115 1.126 1.020 0.559 0.416 0.403 0.911 1.032 0.849 0.861 0.934 0.988 1.064 20.140 133.970 1.480 72.848 18.160 1.049 3.933 1.320 1.423 1.192 1.192 0.875 0.830 1.068 1.209 0.997 1.112 1.123 1.493 1.327 0.126 0.821 0.002 1.878 0.230 0.918 1.317 0.950 0.900 0.837 0.266 0.191 0.195 0.767 0.880 0.734 0.676 0.801 0.602 0.858 1.051 8.473 0.038 12.081 3.148 0.980 2.928 1.125 1.142 0.987 0.570 0.402 0.403 0.906 1.032 0.868 0.895 0.978 0.935 1.084 Journal of Environmental and Public Health Predictor Block one U.S. Region Southeast versus Northeast Midwest versus Northeast West versus Northeast Urbanicity 250 K − 1M versus Metro > 1 M <250 K versus Metro >1 M Patient ZIP code area Program ZIP code area Block two Block three Age 30–43 versus 18–29 43–81 versus 18–29 Female Race/Ethnicity Hispanic versus white Black versus white Other versus white Employed Block four Pain a reason for treatment First methadone treatment Strong urge to use Severe withdrawal Prescription opioid use in past 30 days Heroin use in past 30 days Patient ZIP code area and program ZIP code area are continuous measures; all other covariates are coded 0, 1. We also found that 8% of all patients crossed a state border to attend their OTP and that among a small number (10) of OTPs more than 20% of patients commuted across a state border. Minorities were less likely to cross a state border as well as patients whose OTP was located in the West (compared to the Northeast), in a metropolitan area or in smaller ZIP code area. 4.2. Discussion of Findings. Patients in the Southeast and Midwest traveled greater distances to treatment programs than patients in the Northeast. These regional diﬀerences cannot be entirely explained by regional diﬀerences in urbanicity, because urbanicity was included on the same block with USA region. Future research could determine whether individuals residing in the Southeast and Midwest regions travel greater distances because there may be pro- portionally fewer programs per opioid-dependent patient in those regions. We also found a lower likelihood of cross- state travel to an OTP located in the West versus Northeast (OR = .038). The small odds ratio suggests a large eﬀect but the wide conﬁdence interval (.002 to .839) suggests not much precision in estimating that eﬀect. When these two regions are compared, commuting may be more common in the Northeast because smaller states are closer together and less common in the West because states are larger. The wide conﬁdence interval (as well as the wide conﬁdence interval for Midwest versus Northeast) is likely due to the small number of programs in the West and Midwest regions (see map) and the relatively small percentage of clients who commute across states to an OTP. Patients who enrolled in an OTP located in low or moderately populated counties traveled greater distances than patients in densely populated urban areas. (A similar pattern was also observed for cross-state commuting.) These 8.737 87.475 0.839 77.697 42.997 1.046 6.510 1.332 1.448 1.164 1.220 0.847 0.829 1.072 1.211 1.026 1.185 1.194 1.450 1.369 7