Adjusted Odds Ratio	p-value
	(95% Confidence Interval)
Gender, Female	1.55 (1.37–1.76)	<0.001
Age Category (years)
18–39	Reference
40–59	0.85 (0.70–1.01)	0.070
60–79	1.23 (1.02–1.48)	0.028
80+	1.20 (0.93–1.55)	0.150
Race
White	Reference
Black	0.79 (0.62–1.01)	0.057
Hispanic	0.73 (0.56–0.94)	0.017
Other	0.79 (0.58–1.06)	0.114
Missing	0.88 (0.71–1.10)	0.266
Income Quartile by Zip Code
$1–24,999	Reference
$25,000–34,999	1.06 (0.89–1.26)	0.504
$35,000–44,999	1.22 (1.00–1.48)	0.046
$45,000+	1.24 (1.04–1.49)	0.018
Surgery Type
Pneumonectomy/Lobectomy	Reference
Colectomy	0.75 (0.59–0.95)	0.019
Spinal Fusion	0.91 (0.70–1.18)	0.463
CABG	0.26 (0.17–0.38)	<0.001
Hysterectomy	0.45 (0.35–0.60)	<0.001
Hip Arthroplasty	0.58 (0.43–0.77)	<0.001
Comorbid Diseases:
Chronic Obstructive Pulmonary Disease	1.53 (1.28–1.83)	<0.001
Asthma	1.43 (1.21–1.69)	<0.001
History of Smoking	1.04 (0.91–1.18)	0.60
Coronary Artery Disease	1.01 (0.84–1.21)	0.94
Cerebrovascular Disease	1.08 (0.56–2.09)	0.81
Liver Disease	1.49 (1.08–2.04)	0.01
Renal Disease	3.36 (2.77–4.09)	<0.001
Diabetes	1.14 (0.98–1.31)	0.08
Obese	1.37 (1.17–1.61)	<0.001
Solid Tumor	1.02 (0.86–1.21)	0.81
Hematologic Malignancy	1.01 (0.62–1.64)	0.97
Metastatic Cancer	1.33 (1.05–1.67)	0.02
Rheumatoid Arthritis	1.04 (0.74–1.46)	0.83
Osteoarthritis	1.21 (0.96–1.52)	0.11
History of Substance Abuse	14.81 (12.74–17.21)	<0.001
History of Chronic Pain	2.09 (1.57–2.80)	<0.001
Mood Disorder	1.58 (1.36–1.84)	<0.001
Urban Hospital	0.75 (0.54–1.03)	0.07
Teaching Hospital	1.13 (0.96–1.32)	0.14
Hospital Size
Small	Reference
Medium	1.07 (0.86–1.34)	0.54
Large	1.19 (0.96–1.46)	0.11
Year
2002	Reference
2003	0.84 (0.60–1.19)	0.32
2004	0.94 (0.71–1.25)	0.68
2005	1.26 (0.83–1.90)	0.27
2006	1.08 (0.79–1.48)	0.64
2007	1.04 (0.73–1.49)	0.84
2008	1.24 (0.92–1.69)	0.16
2009	1.20 (0.88–1.64)	0.24
2010	1.12 (0.81–1.54)	0.50
2011	1.17 (0.86–1.60)	0.31
Geographic Location
Northeast	Reference
Midwest	1.53 (1.15–2.04)	0.004
South	0.94 (0.75–1.16)	0.55
West	1.67 (1.33–2.09)	<0.001