Table 4. HRs and 95% CIs of the incidence of BTC and IHBDC according to smoking stratified by drinking status in men.
| Non/Occasional Drinker | Regular Drinker | |||||||||||
| Person-years | Cases | IR per 100,000 | HRa | 95% CI | Person-years | Cases | IR per 100,000 | HRb | 95% CI | |||
| Lower | Upper | Lower | Upper | |||||||||
| IHBDC | ||||||||||||
| Never smoker | 81,698.9 | 8 | 9.8 | 1.00 | 131,361.1 | 6 | 4.6 | 1.00 | ||||
| Former smoker | 59,790.5 | 2 | 3.3 | 0.30 | 0.06 | 1.44 | 139,454.3 | 10 | 7.2 | 1.47 | 0.53 | 4.07 |
| Current smoker (<30 pack-years) | 55,076.9 | 2 | 3.6 | 0.48 | 0.10 | 2.31 | 141,622.3 | 17 | 12.0 | 3.57 | 1.39 | 9.22 |
| Current smoker (≥30 pack-years) | 68,467.6 | 9 | 13.1 | 1.33 | 0.50 | 3.54 | 168,945.8 | 26 | 15.4 | 3.48 | 1.41 | 8.61 |
| P-trend | 0.461 | 0.001 | ||||||||||
| P-interaction | 0.224 | |||||||||||
| BTC | ||||||||||||
| Never smoker | 81,698.9 | 22 | 26.9 | 1.00 | 131,361.1 | 45 | 34.3 | 1.00 | ||||
| Former smoker | 59,790.5 | 23 | 38.5 | 1.11 | 0.61 | 2.02 | 139,454.3 | 48 | 34.4 | 0.87 | 0.58 | 1.32 |
| Current smoker (<30 pack-years) | 55,076.9 | 6 | 10.9 | 0.60 | 0.24 | 1.49 | 141,622.3 | 30 | 21.2 | 0.85 | 0.53 | 1.36 |
| Current smoker (≥30 pack-years) | 68,467.6 | 32 | 46.7 | 1.64 | 0.94 | 2.86 | 168,945.8 | 40 | 23.7 | 0.66 | 0.43 | 1.03 |
| P-trend | 0.117 | 0.068 | ||||||||||
| P-interaction | 0.023 | |||||||||||
| Subtypes of BTC | ||||||||||||
| GBC | ||||||||||||
| Never smoker | 81,698.9 | 6 | 7.3 | 1.00 | 131,361.1 | 12 | 9.1 | 1.00 | ||||
| Former smoker | 59,790.5 | 8 | 13.4 | 1.48 | 0.50 | 4.35 | 139,454.3 | 15 | 10.8 | 1.03 | 0.48 | 2.23 |
| Current smoker (<30 pack-years) | 55,076.9 | 0 | 0 | 0 | — | — | 141,622.3 | 10 | 7.1 | 1.06 | 0.45 | 2.52 |
| Current smoker (≥30 pack-years) | 68,467.6 | 12 | 17.5 | 2.41 | 0.88 | 6.58 | 168,945.8 | 7 | 4.1 | 0.44 | 0.17 | 1.14 |
| P-trend | 0.136 | 0.105 | ||||||||||
| P-interaction | 0.040 | |||||||||||
| EHBDC | ||||||||||||
| Never smoker | 81,698.9 | 14 | 17.1 | 1.00 | 131,361.1 | 26 | 19.8 | 1.00 | ||||
| Former smoker | 59,790.5 | 12 | 20.1 | 0.89 | 0.40 | 1.94 | 139,454.3 | 27 | 19.4 | 0.81 | 0.47 | 1.39 |
| Current smoker (<30 pack-years) | 55,076.9 | 5 | 9.1 | 0.75 | 0.27 | 2.11 | 141,622.3 | 15 | 10.6 | 0.71 | 0.37 | 1.36 |
| Current smoker (≥30 pack-years) | 68,467.6 | 15 | 21.9 | 1.15 | 0.55 | 2.41 | 168,945.8 | 26 | 15.4 | 0.68 | 0.39 | 1.19 |
| P-trend | 0.734 | 0.178 | ||||||||||
| P-interaction | 0.347 | |||||||||||
BTC, biliary tract cancer; CI, confidence interval; EHBDC, extrahepatic bile duct cancer; GBC, gallbladder cancer; HR, hazard ratio; IHBDC, intrahepatic bile duct cancer; IR, incidence ratio.
aAdjusted for age, study area, body mass index, history of cholelithiasis, history of diabetes mellitus, history of chronic hepatitis or cirrhosis, Japanese tea consumption, and alcohol consumption (non-drinker vs occasional drinker).
bAdjusted for age, study area, body mass index, history of cholelithiasis, history of diabetes mellitus, history of chronic hepatitis or cirrhosis, Japanese tea consumption, and alcohol consumption (<300 g/week of ethanol vs ≥300 g/week of ethanol).