Table 1 Demographic characteristics of the Tet and control groups

Age(yrs)

55.3 ± 7.4

55.4 ± 8.4

55.4 ± 6.6

0.970

Smoking status (pack-years)n(%)

 0

28(23.5)

15(26.8)

13(20.6)

 1–19

31(26.1)

14(25.0)

17(27.0)

 ≥ 20

60(50.4)

27(45.0)

33(55.0)

0.732

Worked as a driller n(%)

 Yes

92(72.4)

38(66.7)

54(77.8)

 No

34(27.6)

19(33.3)

16(22.2)

0.145

Exposure duration

13.9 ± 7.6

13.6 ± 7.7

14.1 ± 7.6

0.680

Age at onset of dust exposure (yrs)

24.8 ± 7.6

25.0 ± 7.3

24.7 ± 7.5

0.806

Age at the end of dust exposure (yrs)

42.8 ± 8.2

42.1 ± 8.2

43.4 ± 8.2

0.403

Diagnosis n(%)

 Coal Worker’ pneumoconiosis

75/127(59.1)

31(54.4)

44(62.9)

 Silicosis

52/127(40.9)

26(45.6)

26(37.1)

0.368

Interval of follow-upon (month) [M(P25, 75)]

13(12, 16)

13(12, 13)

15(12, 16)

0.080