Table 2.

Factors related to the use of tramadol or stronger opioids compared with non-use in knee OA patients

Variables	Tramadol (OR, 95% CI)	Stronger opioids (OR, 95% CI)
Year
2013 (reference)	1	1
2014	1.00 (0.99–1.01)	1.40 (1.26–1.56)
2015	0.98 (0.97–0.99)	1.14 (1.02–1.28)
Age
50–59 (reference)	1	1
60–69	0.97 (0.96–0.98)	0.99 (0.87–1.12)
≥ 70	1.01 (1.00–1.02)	1.45 (1.29–1.63)
Sex
Female (reference)	1	1
Male	1.28 (1.27–1.29)	1.13 (1.03–1.24)
Health insurance
Medical aid/veterans (reference)	1	1
National insurance	0.94 (0.93–0.96)	0.73 (0.64–0.83)
Type of institution
Hospital/clinic (reference)	1	1
Tertiary hospital	1.04 (1.01–1.07)	59.63 (52.27–68.04)
General hospital	0.97 (0.96–0.99)	21.19 (18.90–23.75)
Others	0.12 (0.12–0.13)	0.06 (0.02–0.13)
Type of department
Internal medicine (reference)	1	1
Orthopedics	1.00 (0.99–1.01)	0.46 (0.41–0.52)
Rehabilitation	0.81 (0.79–0.84)	0.30 (0.23–0.40)
Others	0.95 (0.94–0.97)	0.87 (0.76–1.01)
Myocardial infarction	0.96 (0.93–0.99)	1.12 (0.84–1.51)
Congestive heart failure	1.01 (1.00–1.03)	1.08 (0.93–1.26)
Peripheral vascular disease	1.04 (1.03–1.05)	1.07 (0.95–1.20)
Dementia	0.98 (0.97–1.00)	1.24 (1.07–1.43)
Chronic pulmonary disease	1.00 (0.99–1.01)	1.16 (1.06–1.28)
Peptic ulcer disease	1.03 (1.02–1.04)	1.09 (0.99–1.20)
Diabetes	0.97 (0.96–0.98)	1.21 (1.10–1.33)
Any malignancy	0.87 (0.85–0.88)	2.91 (2.60–3.25)
Alcohol abuse	1.01 (0.99–1.04)	1.39 (1.10–1.75)
Depression	1.05 (1.04–1.06)	1.46 (1.31–1.62)
Low back pain	1.13 (1.12–1.13)	1.30 (1.18–1.43)
Intervertebral disc disorder	1.11 (1.10–1.12)	1.40 (1.26–1.56)
Spinal stenosis	1.27 (1.26–1.28)	1.55 (1.40–1.72)
Fibromyalgia	1.13 (1.10–1.16)	0.93 (0.69–1.26)

OA osteoarthritis, OR odds ratio, CI confidence interval