Skip to main content

Table 2 Predictors of silicosis (ILO grade > 1/1): unadjusted and adjusted models (N = 14,213)a

From: Predictors of silicosis and variation in prevalence across mines among employed gold miners in South Africa

Exposure

Unadjusted model

Adjusted model A

Adjusted model Bb

Odds Ratio (95% CI)

Odds Ratio (95% CI)

p

Odds Ratio (95% CI)

p

Cluster

1

1.0

1.0

< 0.001

  

2

0.84 (0.51; 1.41)

1.73 (1.03; 2.92)

 

3

0.82 (0.41; 1.66)

1.45 (0.70; 2.97)

 

4

1.55 (1.00; 2.38)

2.22 (1.42; 3.48)

 

5

0.99 (0.61; 1.59)

1.78 (1.09; 2.90)

 

6

2.11 (1.41; 3.15)

4.41 (2.91; 6.69)

 

7

0.79 (0.48; 1.32)

1.4 (0.83; 2.34)

 

8

0.39 (0.21; 0.73)

0.66 (0.35; 1.26)

 

9

1.07 (0.63; 1.79)

1.79 (1.05; 3.05)

 

10

1.97 (1.32; 2.94)

3.53 (2.34; 5.34)

 

11

1.70 (1.12; 2.57)

1.81 (1.18; 2.76)

 

12

0.81 (0.51; 1.31)

2.03 (1.24; 3.32)

 

13

0.25 (0.12; 0.52)

0.42 (0.20; 0.88)

 

14

0.86 (0.54; 1.37)

1.72 (1.06; 2.78)

 

15

1.28 (0.83; 1.98)

1.59 (1.02; 2.49)

 

Region

Carletonville

1.0

 

1.0

0.035

Orkney

1.30 (1.06; 1.6)

0.87 (0.68; 1.12)

Welkom

1.58 (1.28; 1.96)

1.43 (1.05; 1.93)

Company

A

1.0

 

1.0

0.115

B

0.64 (0.50; 0.81)

0.76 (0.54; 1.05)

C

1.10 (0.91; 1.33)

0.96 (0.69; 1.35)

Gender

Male

1.0

1.0

0.729

1.0

0.674

Female

0.15 (0.04; 0.62)

1.31 (0.3; 5.77)

1.39 (0.32; 6.11)

Age (years)

18–34

1.0

1.0

< 0.001

1.0

< 0.001

35–39

3.10 (1.38; 6.96)

1.73 (0.66; 4.55)

1.67 (0.64; 4.37)

40–44

9.16 (4.58; 18.36)

3.1 (1.17; 8.17)

2.92 (1.11; 7.65)

45–49

23.93 (12.23; 46.83)

5.77 (2.17; 15.38)

5.34 (2.01; 14.14)

50+

37.29 (19.15; 72.62)

7.25c (2.68; 19.64)

6.5c (2.41; 17.51)

Racial ascription

Other

1.0

1.0

0.146

1.0

0.016

Black

3.41 (1.40; 8.26)

2.81 (1.09; 7.21)

2.79 (1.09; 7.15)

Country of origina

South Africa

1.0

1.0

< 0.001

1.0

0.004

Lesotho

1.72 (1.42; 2.08)

1.16 (0.95; 1.42)

1.16 (0.95; 1.42)

Swaziland

1.15 (0.73; 1.81)

0.84 (0.53; 1.34)

0.90 (0.57; 1.43)

Mozambique

0.72 (0.52; 1.00)

0.54 (0.38; 0.77)

0.61 (0.43; 0.86)

Botswana

2.3 (1.36; 3.88)

1.09 (0.63; 1.88)

1.06 (0.62; 1.82)

Years since entry into industry

0–4

1.0

1.0

< 0.001

1.0

< 0.001

5–9

2.54 (0.80; 8.04)

2.31 (0.71; 7.58)

2.20 (0.67; 7.19)

10–14

3.23 (1.13; 9.20)

2.04 (0.62; 6.71)

2.17 (0.66; 7.12)

15–19

9.39 (3.69; 23.88)

3.89 (1.2; 12.63)

4.19 (1.30; 13.51)

20–24

17.40 (7.06; 42.89)

5.53 (1.7; 17.98)

5.75 (1.78; 18.59)

25–29

33.52 (13.71; 81.93)

7.55 (2.3; 24.72)

7.93 (2.43; 25.82)

30+

52.06 (21.43; 126.47)

10.12b (3.06; 33.41)

10.65b (3.24; 34.99)

Skill level

Skilled/Official

1.0

1.0

0.234

1.0

0.179

Unskilled

1.76 (1.20; 2.58)

1.28 (0.84; 1.94)

1.26 (0.83; 1.92)

Under

ground work

None/part time

1.0

1.0

< 0.001

1.0

< 0.001

Full time

0.52 (0.33; 0.81)

2.15 (1.35; 3.43)

2.14 (1.34; 3.42)

  1. p = Likelihood Ratio Test for exclusion of the relevant variable from the model
  2. aEight individuals from Namibia and Zimbabwe (“other” origin), none with silicosis, were excluded
  3. bShaft was replaced by region and company in Model B
  4. cp for linear trend < 0.001 in both models