Table 4.

OR with 95% CI for the development of COPD in pneumoconiosis patients according to multiple logistic regression analysis

Variable	Univariate analysis		Multivariate analysis
	OR(95%CI)	P value	OR(95%CI)	P value
Age	2.31(1.68,3.19)	0.00**	0.90(0.87,0.93)	0.00**
BMI	0.83(0.60,1.17)	0.29	1.09(1.00,1.18)	0.043*
Smoking	1.01(0.91,1.32)	0.32	0.99(0.98,1.01)	0.30
Exposure time	1.18(0.91,1.54)	0.21	0.99(0.96,1.02)	0.44
Air drill type	1.46(0.90,2.37)	0.12	1.38(0.84,2.26)	0.21
Exposure type	1.13(0.61,2.07)	0.70	1.29(0.68,2.45)	0.43
Category	3.29(2.49,4.35)	0.00**	10.92(6.20,19.24)	0.00**
			4.39(2.29,8.41)	0.00**
Cough	1.73(0.42,7.12)	0.45	1.76(0.42,7.38)	0.44
Sputum	0.51(0.14,1.82)	0.30	0.50(0.14,1.79)	0.29
Wheezing	2.84(1.74,4.60)	0.00**	2.94(1.79,4.83)	0.00**
Dyspnea	1.08(0.37,3.13)	0.89	1.12(0.38,3.34)	0.83
Chest tightness	0.98(0.51,1.90)	0.96	0.93(0.48,1.82)	0.83

In univariate analysis model:

Age (1 = 21–30,2 = 31–40,3 = 41–50,4 = 51–60,5 = 61–70,6 = 71–80)

BMI (1 = Below normal, 2 = Normal, 3 = Overweight, 4 = Obesity)

Smoking (1 = Never smokers, 2 = Mild smokers, 3 = Moderate smokers, 4 = Heavy smokers)

Exposure time (1 = 0–10, 2 = 11–20, 3 = 21–30, 4 = 31–40)

Air drill type (1 = No, 2 = Yes)

Exposure type (1 = Silicosis, 2 = Coal)

Category (1 = I, 2 = II, 3 = III)

Cough: 1 = No, 2 = Yes, Sputum: 1 = No, 2 = Yes, Wheezing: 1 = No, 2 = Yes, Dyspnea: 1 = No, 2 = Yes,

Chest tightness:1 = No, 2 = Yes

In multivariate analysis, age, BMI, exposure time and SI were taken as covariate

OR odd ratio, CI confidence interval

*p<0.05, **p<0.01