Table 4

Logistic regression model for 651 patients with combined COPD and pneumoconiosis*

	Univariate analysis			Multivariate analysis
	OR	95% CI	P value	OR	95% CI	P value
Age, years
20–39	1.00	(ref)		1.00	(ref)
40–59	3.86	1.14 to 13.06	0.030	2.33	0.64 to 8.54	0.202
≥60	3.46	1.01 to 11.82	0.048	3.76	0.97 to 14.7	0.056
Male gender	1.22	0.81 to 1.83	0.340	0.81	0.43 to 1.50	0.498
Smoking exposure, pack-years
0	1.00	(ref)		1.00	(ref)
1–19	1.01	0.68 to 1.49	0.980	0.92	0.55 to 1.56	0.761
≥20	2.01	1.32 to 3.06	0.001	1.91	1.10 to 3.32	0.022
BMI†, kg/m²
<18.5	1.05	0.19 to 5.85	0.952	0.54	0.79 to 3.67	0.527
18.5–24.9	1.00	(ref)		1.00	(ref)
≥25.0	0.87	0.63 to 1.22	0.431	1.09	0.75 to 1.58	0.664
Exposure duration, years
0–15	1.00	(ref)		1.00	(ref)
16–30	1.25	0.86 to 1.82	0.233	0.78	0.51 to 1.19	0.246
31–45	1.48	0.81 to 2.71	0.207	1.28	0.62 to 2.64	0.503
Exposure type
Asbestos	1.00	(ref)		1.00	(ref)
Silica	2.48	1.44 to 4.25	0.001	2.42	1.28 to 4.59	0.007
Coal	2.86	1.70 to 4.79	<0.001	3.19	1.57 to 6.49	0.001
Other dust	1.05	0.50 to 2.19	0.895	1.89	0.80 to 4.46	0.147
Stage of pneumoconiosis
Ⅰ/Ⅱ	1.00	(ref)		1.00	(ref)
Ⅲ	5.05	3.44 to 7.41	<0.001	4.85	3.18 to 7.42	<0.001
BDT
Negative	1.00	(ref)		1.00	(ref)
Positive	2.07	0.76 to 5.61	0.153	2.17	0.67 to 7.01	0.197

*The patients with BMI <18.5 kg/m² means under weight, 18.5 to 24.9 kg/m² means normal range and ≥25.0 kg/m² means overweight and obese.
†All variables in the table were included in the multivariate model, while adjusting for age, sex, BMI, exposure duration and BDT.
BDT, bronchial dilation test; BMI, body mass index; COPD, chronic obstructive pulmonary disease; ; ref, reference.