Table 1 Predictors selection for the prognosis of silicosis using univariate Cox regression model.
Variables | N (%) | Coefficient | HR (95%CI) | Wald X 2 | df | p | |
|---|---|---|---|---|---|---|---|
Age at first exposure to silica dust (years) | 7.60 | 3 | 0.055 | ||||
<20 | 526 (15.06) | 0 | 1.00 | ||||
20 ~ 24 | 654 (18.73) | −0.04 | 0.96 (0.72—1.28) | 0.06 | 1 | 0.800 | |
25–29 | 1185 (33.93) | 0.36 | 1.43 (1.05–1.96) | 5.14 | 1 | 0.023 | |
>=30 | 1127 (32.27) | 0.16 | 1.18 (0.83–1.68) | 0.83 | 1 | 0.363 | |
Age at entry of the cohort (years) | 155.06 | 4 | <0.001 | ||||
<20 | 606 (17.35) | 0 | 1.00 | ||||
20 ~ 24 | 888 (25.43) | 1.26 | 3.53 (1.36–9.20) | 6.69 | 1 | 0.010 | |
25–29 | 813 (23.28) | 2.23 | 9.38 (3.77–23.32) | 23.19 | 1 | <0.001 | |
30 ~ 34 | 544 (15.58) | 3.06 | 21.26 (8.64–52.32) | 44.25 | 1 | <0.001 | |
>=35 | 641 (18.36) | 3.30 | 27.12 (11.09–66.33) | 52.34 | 1 | <0.001 | |
Mean concentration of respirable silica dust (mg/m3) | 282.95 | 3 | <0.001 | ||||
<0.05 | 969 (27.75) | 0 | 1.00 | ||||
0.05 ~ 0.10 | 1715 (49.11) | 2.14 | 8.52 (3.96–18.33) | 30.05 | 1 | <0.001 | |
0.10 ~ 0.15 | 542 (15.52) | 3.41 | 30.28 (14.08–65.13) | 76.17 | 1 | <0.001 | |
>=0.15 | 266 (7.62) | 4.23 | 68.64 (31.83–147.98) | 116.39 | 1 | <0.001 | |
Net years of dust exposure (years) | 110.52 | 4 | <0.001 | ||||
<10 | 332 (9.51) | 0 | 1.00 | ||||
10 ~ 15 | 303 (8.68) | 1.21 | 3.36 (1.91–5.91) | 17.58 | 1 | <0.001 | |
15 ~ 20 | 367 (10.51) | 1.14 | 3.12 (1.79–5.45) | 15.96 | 1 | <0.001 | |
20 ~ 25 | 558 (15.98) | 1.10 | 2.99 (1.76–5.11) | 16.19 | 1 | <0.001 | |
>=25 | 1932 (55.33) | −0.14 | 0.87 (0.51–1.48) | 0.27 | 1 | 0.606 | |
No. of jobs experienced in the iron ore | 43.77 | 2 | <0.001 | ||||
1 job | 1345 (38.52) | 0 | 1.00 | ||||
2 jobs | 1342 (38.43) | 0.86 | 2.37 (1.74–3.23) | 30.22 | 1 | <0.001 | |
3 jobs or more | 805 (23.05) | 1.06 | 2.89 (2.09–4.00) | 41.28 | 1 | <0.001 | |
Smoking habits | |||||||
Non-smoker | 790 (22.62) | 0 | 1.00 | ||||
Ever smoker | 2702 (77.38) | 0.35 | 1.41 (1.05—1.91) | 5.08 | 1 | 0.024 | |
Illiteracy a | |||||||
No | 1734 (49.66) | 0 | 1.00 | ||||
Yes | 1758 (50.34) | 0.13 | 2.69 (2.10–3.44) | 60.75 | 1 | <0.001 | |
Married status | |||||||
Married | 3376 (96.68) | 0 | 1.00 | ||||
Unmarried | 116 (3.32) | 0.14 | 1.15 (0.64-2.04) | 0.21 | 1 | 0.645 | |
History of lung diseases b | |||||||
Pulmonary tuberculosis | 57 (1.63) | 0.16 | 1.17 (0.52–2.63) | 0.15 | 1 | 0.097 | |
Chronic bronchitis | 207 (5.93) | −0.57 | 0.56 (0.31–1.03) | 3.49 | 1 | 0.062 | |
Asthma | 34 (0.97) | −0.04 | 0.97 (0.31–3.01) | 0.01 | 1 | 0.952 | |
