Table 3.

Unadjusted and Adjusted (final) Cox Regression Models for Predicting 2-Year Overdose Risk for Patients Prescribed Chronic Opioid Therapy at the Derivation Site

Characteristic	Unadjusted model	Adjusted model*
	Hazard ratio (95 CI†)	β coefficient	Hazard ratio (95 CI†)
Age (per year)	0.93 (0.88–0.98) ‡	−0.06915	0.93 (0.89–0.98)
Age-squared	1.00 (1.00–1.00) ‡	0.0005626	1.00 (1.00–1.00)
Mental health diagnosis§	4.18 (2.88–6.07)	1.22076	3.39 (2.32–4.96)
Psychotropic prescription	2.82 (1.88–4.25)
Substance abuse/dependence diagnosis||	6.01 (4.03–8.96)	1.24387	3.47 (2.25–5.36)
Tobacco use or tobacco abuse/dependence diagnosis¶	2.31 (1.60–3.32)	0.42788	1.53 (1.03–2.28)
History of opioid prescriptions in the year prior to initiating chronic opioid therapy	1.43 (1.00–2.05)
Long-acting or extended-release opioid formulation	2.47 (1.25–4.87)	0.68552	1.99 (1.00–3.93)
Daily opioid dose (per 10 mg morphine equivalents)**	1.01 (0.99–1.03)
Hepatitis C diagnosis††	2.82 (1.04–7.63)

*S₀(2) = 0.99768 (2-year baseline survival)

^†CI, confidence interval

^‡Age and age-squared included together in the unadjusted model

^§Identified using ICD-9 codes 295, 296, 297, 298, 300, 301, 309, 311

^||Included drug and alcohol abuse and dependence. Identified using ICD-9 codes 292, 304, 305.2, 305.3, 305.4, 305.5, 305.6, 305.7, 305.8, 305.9, V65.42, 291, 303, 303.0, 303.9, 305.0, 357.5, 425.5, 535.3, 571.0, 571.1, 571.2, 571.3, 980, V11.3

^¶Based on information in the electronic social history table or ICD-9 code 305.1

**Calculated for each prescription by multiplying the quantity of each prescription by the strength of the prescription and then multiplying by a conversion factor. MMEs were then added together for all the prescriptions on the index date

^††Identified using ICD-9 codes 070.41, 070.44, 070.51, 070.54, 070.7, 070.70, 070.71