Age | Total | Surface work | Underground work | Surface vs underground | Underground work by number of years* | ||||||
n† | SMR(95% CI) | n† | SMR(95% CI) | n† | SMR(95% CI) | RR(95% CI) | Number of years | n† | SMR(95% CI) | RR(95% CI) | |
⩽60 years | 371 | 1.35 (1.22 to 1.50) | 115 | 1.47 (1.21 to 1.76) | 256 | 1.30 (1.15 to 1.48) | 0.89 (0.71 to 1.01) | 0–5 | 88 | 1.21 (0.97 to 1.50) | 1– |
5–15 | 84 | 1.23 (0.98 to 1.52) | 1.02 (0.75 to 1.37) | ||||||||
>15 | 84 | 1.51 (1.21 to 1.87) | 1.25 (0.93 to 1.68) | ||||||||
>60 years | 1106 | 1.06 (1.00 to 1.13) | 307 | 1.02 (0.91 to 1.14) | 799 | 1.08 (1.00 to 1.16) | 1.06 (0.93 to 1.21) | 0–5 | 189 | 0.97 (0.83 to 1.11) | 1– |
5–15 | 272 | 1.10 (0.97 to 1.23) | 1.13 (0.94 to 1.37) | ||||||||
>15 | 338 | 1.14 (1.02 to 1.26) | 1.18 (0.98 to 1.40) | ||||||||
Total | 1477 | 1.12 (1.07 to 1.18) | 422 | 1.11 (1.01 to 1.22) | 1055 | 1.13 (1.06 to 1.20) | 1.02 (0.91 to 1.14) | 0–5 | 277 | 1.03 (0.92 to 1.16) | 1– |
5–15 | 356 | 1.13 (1.01 to 1.25) | 1.10 (0.94 to 1.28) | ||||||||
>15 | 422 | 1.20 (1.08 to 1.32) | 1.17 (1.00 to 1.36) |
*Cumulative employment time; †number of cases. Comparison of mortality rates between surface and underground workers (surface vs underground) are based on Poisson regression. RR, relative risk; SMR, standardised mortality ratio.