Table 2.
HRs for total and cause-specific mortality associated with silica exposure in the cohort (n = 7,665), 1960–2012
| Cause of death (ICD-10) | Number of deaths | HRs for per 1 mg/m3-y increase in CDE | HRs for silica exposure levels versus unexposeda | |||
|---|---|---|---|---|---|---|
| Low | Medium | High | p-Valueb | |||
| Malignant neoplasm (C00-C97) | 789 | 1.048 (0.962, 1.142) | 1.531 (1.241, 1.890) | 1.378 (1.137, 1.669) | 1.238 (1.025, 1.494) | 0.009 |
| Malignant neoplasm of oesophagus (C15) | 66 | 0.952 (0.693, 1.307) | 1.335 (0.648, 2.753) | 1.511 (0.795, 2.874) | 1.249 (0.644, 2.420) | 0.384 |
| Malignant neoplasm of stomach (C16) | 104 | 1.130 (0.931, 1.373) | 1.980 (1.153, 3.401) | 1.380 (0.800, 2.379) | 1.367 (0.814, 2.295) | 0.223 |
| Malignant neoplasm of liver and intrahepatic bile ducts (C22) | 152 | 0.774 (0.585, 1.025) | 1.512 (0.972, 2.353) | 1.060 (0.681, 1.648) | 0.774 (0.487, 1.229) | 0.359 |
| Lung cancer (C33-C34) | 262 | 1.190 (1.049, 1.349) | 1.671 (1.132, 2.466) | 1.663 (1.193, 2.318) | 1.671 (1.216, 2.298) | 0.001 |
| Certain infectious and parasitic diseases (A00-B99, J65) | 89 | 1.204 (1.018, 1.423) | 1.073 (0.520, 2.212) | 1.560 (0.882, 2.761) | 1.790 (1.064, 3.010) | 0.020 |
| Respiratory tuberculosis (A15-A16, J65) | 58 | 1.226 (1.017, 1.477) | 0.523 (0.153, 1.785) | 1.459 (0.695, 3.061) | 2.532 (1.383, 4.635) | 0.002 |
| Cardiovascular disease (I00-I52, I70-I99) | 372 | 1.213 (1.117, 1.318) | 0.986 (0.672, 1.447) | 1.373 (1.030, 1.831) | 1.723 (1.345, 2.206) | < 0.001 |
| Ischaemic heart disease (I20-I25) | 219 | 1.134 (0.990, 1.298) | 1.190 (0.738, 1.918) | 1.538 (1.063, 2.226) | 1.781 (1.281, 2.476) | < 0.001 |
| Pulmonary heart disease (I26-I27) | 66 | 1.352 (1.197, 1.529) | 0.562 (0.168, 1.880) | 1.258 (0.615, 2.573) | 2.009 (1.160, 3.479) | 0.010 |
| Cerebrovascular disease (I60-I69) | 388 | 0.973 (0.859, 1.103) | 0.950 (0.670, 1.345) | 1.234 (0.945, 1.613) | 0.945 (0.724, 1.233) | 0.995 |
| Disease of the respiratory system (J00-J99) | 324 | 1.414 (1.329, 1.505) | 2.817 (1.927, 4.118) | 2.714 (1.954, 3.768) | 3.615 (2.718, 4.807) | < 0.001 |
| Pneumoconiosis (J60-J65) | 110 | 1.384 (1.255, 1.525) | 1.000 (reference) | 2.245 (0.912, 5.524) | 5.312 (2.298, 12.280) | < 0.001 |
| Chronic lower respiratory disease (J40-J47) | 142 | 1.264 (1.115, 1.434) | 2.759 (1.688, 4.507) | 2.060 (1.304, 3.253) | 1.720 (1.106, 2.675) | 0.012 |
| Disease of the digestive system (K00-K93) | 95 | 0.877 (0.635, 1.211) | 1.467 (0.831, 2.587) | 1.065 (0.605, 1.874) | 0.838 (0.468, 1.499) | 0.629 |
| Fibrosis and cirrhosis of liver (K74) | 63 | 0.770 (0.487, 1.218) | 1.302 (0.651, 2.601) | 1.079 (0.549, 2.121) | 0.714 (0.335, 1.524) | 0.488 |
| External causes of morbidity and mortality (V01-Y98) | 193 | 0.883 (0.702, 1.110) | 2.839 (1.996, 4.038) | 1.145 (0.745, 1.761) | 0.928 (0.591, 1.458) | 0.953 |
| All diseases (A00-Y98) | 2814 | 1.117 (1.074, 1.162) | 1.368 (1.218, 1.537) | 1.246 (1.121, 1.383) | 1.313 (1.192, 1.447) | < 0.001 |
HRs were calculated by using Cox proportional hazards models, which included the duration of follow-up as time variable and were adjusted for gender, year at hire (five categories: 1955 or earlier, 1956–1960, 1961–1965, 1966–1970, 1971 or later), age at hire (continuous), and smoking intensity (continuous). Pneumoconiosis mortality risks were estimated only among silica-exposed workers
aThe categorical analyses were conducted on the basis of various silica exposure level, i.e. unexposed, low (0.4935 mg/m3-y or below), medium (0.4935 to 0.8423 mg/m3-y), and high level (0.8423 mg/m3-y or above). The reference category was defined as the unexposed level, except pneumoconiosis, which used low level as reference category
bEvaluated by including the median exposure values within each exposure level as a continuous variable in the model