Table 3 Dose-response relationship between exposure to either passive or active smoking and deaths owing to extrahepatic cholangiocarcinoma
Doses exposed to tobacco | Numbers of outcomes | Numbers of persons observed | ‰ | RR (95% CI) | |
|---|---|---|---|---|---|
(pack-years) | Model 1 | Model 2 | |||
Pathology-based | |||||
 Control | 54 | 4501 | 12.0 | 1.00 | 1.00 |
 Exposure to passive smoking | |||||
  1~9 | 81 | 6976 | 11.6 | 1.13 (0.66–1.96) | 0.94 (0.46–1.95) |
  10~19 | 17 | 1105 | 15.4 | 1.62 (0.90–2.91) | 1.09 (0.51–1.36) |
  ≥ 20 | 40 | 1267 | 31.6 | 1.97 (1.24–3.15) | 1.60 (0.94–2.75) |
  P for trend |  |  |  | < 0.001 | 0.021 |
 Exposure to active smoking | |||||
  1~9 | 70 | 5271 | 13.3 | 1.12 (0.68–1.85) | 0.86 (0.45–1.63) |
  10~19 | 20 | 1646 | 12.2 | 1.59 (0.91–2.75) | 1.26 (0.65–1.41) |
  ≥ 20 | 48 | 2428 | 19.8 | 1.78 (1.15–2.76) | 1.66 (1.03–2.67) |
  P for trend |  |  |  | 0.002 | 0.045 |
Non-pathology-based | |||||
 Control | 96 | 15,627 | 6.1 | 1.00 | 1.00 |
 Exposure to passive smoking | |||||
  1~9 | 95 | 17,933 | 5.3 | 1.04 (0.67–1.63) | 0.79 (0.42–1.48) |
  10~19 | 16 | 3276 | 4.9 | 0.86 (0.50–1.49) | 0.79 (0.41–1.52) |
  ≥ 20 | 52 | 5133 | 10.1 | 1.61 (1.12–2.32) | 1.27 (0.81–1.98) |
  P for trend |  |  |  | 0.013 | 0.220 |
 Exposure to active smoking | |||||
  1~9 | 83 | 14,506 | 5.7 | 1.08 (0.70–1.64) | 0.73 (0.40–1.34) |
  10~19 | 18 | 3498 | 5.1 | 0.92 (0.55–1.56) | 0.95 (0.53–1.70) |
  ≥ 20 | 62 | 8330 | 7.4 | 1.24 (0.88–1.76) | 1.08 (0.73–1.60) |
  P for trend |  |  |  | 0.066 | 0.431 |