Risk Factor	OR	95% CI	P Value
Age	1.03^a	(1.023, 1.03)	.00
Gender, male	0.69^a	(0.638, 0.753)	.00
Region
East North Central	0.95	(0.776, 1.169)	.64
East South Central	0.97	(0.734, 1.288)	.84
Middle Atlantic	1.01	(0.816, 1.25)	.93
Mountain	0.93	(0.71, 1.223)	.61
New England	1.04	(0.769, 1.402)	.81
West South Central	0.89	(0.697, 1.131)	.33
Pacific (reference group)
South Atlantic	0.82	(0.648, 1.027)	.08
West North Central	1.12	(0.881, 1.424)	.35
Unknown	1.12	(0.894, 1.405)	.32
Clinical characteristics
Comorbidities
Acute renal failure	1.41^a	(1.063, 1.862)	.02
Alcohol use	3.41^a	(2.257, 5.153)	.00
Anxiety	1.31^a	(1.124, 1.539)	.00
Balance impairment	1.40^a	(1.17, 1.684)	.00
Chronic kidney disease	1.05	(0.859, 1.273)	.66
Congestive heart failure	1.03	(0.821, 1.295)	.79
Constipation	1.31^a	(1.06, 1.617)	.01
Depression	1.28^a	(1.096, 1.483)	.00
Fatigue	1.07	(0.947, 1.208)	.28
History of falling	2.19^a	(1.365, 3.5)	.00
Hypertension	1.05	(0.969, 1.14)	.23
Muscle weakness	1.22	(0.965, 1.544)	.10
Myocardial infarction	1.23	(0.774, 1.941)	.39
Nausea	1.26^a	(1.056, 1.502)	.01
Neuropathy	1.26	(0.985, 1.619)	.07
Osteopenia^a	0.69^a	(0.565, 0.854)	.00
Osteoporosis	2.06^a	(1.77, 2.396)	.00
Parkinson’s disease	1.90^a	(1.131, 3.196)	.02
Benzodiazepine use	1.21^a	(1.109, 1.325)	.00
Transient ischemic attack	0.84	(0.546, 1.28)	.41
Vitamin D deficiency	1.11	(0.935, 1.317)	.23
Charlson Comorbidity Index	1.13^a	(1.072, 1.188)	.00
OA diagnosis
Knee (knee only or knee and others) (reference group)
Hip (only or in combination with other OA)	1.05	(0.961, 1.152)	.27
Index drug characteristics
Tramadol (reference group)
Non-tramadol opioids	1.31^a	(1.199, 1.44)	.00
Index opioid dose (in 10s of MME)	1.01^a	(1.002, 1.009)	.00