Table 1 Demographic characteristics and exposures of study participants (n = 2860)

Age group(years)

 40~

465 (17.6)

112 (22.4)

74 (9.6)

26 (3.2)

20 (4.3)

11 (1.7)

9 (2.6)

 50~

1212 (42.8)

291 (21.8)

173 (9.4)

61 (2.8)

136 (10.4)

86 (5.7)

50 (4.7)

 60~

851 (29.0)

240 (26.8)

169 (14.0)

64 (4.7)

141 (17.1)

87 (10.2)

54 (6.9)

 ≥ 70

332 (10.5)

99 (29.2)

98 (17.6)

45 (8.8)

75 (23.7)

53 (15.3)

22 (8.5)

 p value for trend

0.025*

< 0.001***

< 0.001***

< 0.001***

< 0.001***

< 0.001***

Gender

 Male

1683 (56.9)

598 (33.8)

290 (11.3)

149 (5.7)

322 (19.1)

202 (11.1)

120 (8.0)

 Female

1177 (43.1)

144 (11.4)

224 (12.0)

47 (1.8)

50 (4.0)

35 (2.2)

15 (1.8)

 p value

< 0.001***

0.627

< 0.001***

< 0.001***

< 0.001***

< 0.001***

Residence

 Urban

860 (31.9)

171 (14.9)

153 (8.0)

46 (1.6)

70 (5.9)

47 (3.9)

23 (2.0)

 Rural

2000 (68.1)

571 (28.5)

361 (13.3)

150 (5.2)

302 (15.7)

190 (8.8)

112 (6.9)

 p value

< 0.001***

< 0.001***

< 0.001***

< 0.001***

< 0.001***

< 0.001***

Education level

 Primary and lower

1624 (53.3)

401 (22.7)

326 (12.8)

126 (4.7)

215 (13.7)

142 (8.5)

73 (5.2)

 Secondary school

920 (33.4)

257 (26.6)

135 (10.4)

49 (3.2)

119 (12.4)

69 (6.3)

50 (6.1)

 Higher or further education

316 (13.3)

84 (23.9)

53 (9.7)

21 (3.3)

38 (8.8)

26 (4.7)

12 (4.0)

 p value for trend

0.334

0.055

0.101

0.044*

0.015*

0.806

Occupation

 Agriculture

1810 (60.0)

485 (26.1)

277 (12.3)

106 (4.4)

255 (14.7)

150 (8.0)

105 (6.7)

 Non-agriculture

590 (22.0)

166 (25.7)

155 (10.6)

61 (3.7)

81 (11.5)

65 (8.5)

16 (3.0)

 Unemployed and houseworker

409 (15.8)

73 (13.5)

67 (9.4)

23 (3.0)

29 (6.1)

17 (2.2)

12 (3.9)

 Retired

51 (2.2)

18 (29.7)

15 (18.9)

6 (4.7)

7 (13.2)

5 (9.9)

2 (3.4)

 p value

< 0.001***

0.193

0.515

0.004**

0.003**

0.053

Smoking status#

 Never smoker

1654 (60.2)

275 (13.8)

314 (11.7)

85 (2.5)

102 (5.1)

67 (2.8)

35 (2.2)

 Former smoker

264 (8.9)

101 (38.7)

57 (15.1)

33 (9.0)

68 (27.7)

43 (15.7)

25 (12.0)

 Current smoker

940 (30.9)

366 (40.0)

143 (10.4)

78 (5.6)

202 (23.0)

127 (13.5)

75 (9.5)

 p value

< 0.001***

0.154

< 0.001***

< 0.001***

< 0.001***

< 0.001***

Family history of lung diseases

 No

2267(77.2)

551(22.7)

444 (12.4)

166 (4.2)

270 (11.6)

181 (6.7)

89 (4.8)

 Yes

593(22.8)

191(29.0)

70 (9.1)

30 (3.5)

102 (16.0)

56 (8.9)

46 (7.1)

 p value

0.012*

0.054

0.451

0.019*

0.137

0.078

Total

2860 (100.0)

742 (24.1)

514 (11.6)

196 (4.0)

372 (12.6)

237 (7.2)

135 (5.3)