Table 2. HRs and 95% CIs of the incidence of BTC and IHBDC according to smoking in men.

	Cases	IR per 100,000	HRa	95% CI
				Lower	Upper
IHBDC
Never smoker	14	6.6	1.00
Former smoker	12	6.0	0.82	0.38	1.79
Current smoker (<30 pack-years)	19	9.7	1.91	0.94	3.87
Current smoker (≥30 pack-years)	35	14.7	2.25	1.19	4.25
P-trend				0.001
BTC
Never smoker	67	31.4	1.00
Former smoker	71	35.6	0.96	0.68	1.34
Current smoker (<30 pack-years)	36	18.3	0.82	0.54	1.24
Current smoker (≥30 pack-years)	72	30.3	0.94	0.67	1.32
P-trend				0.611
Subtypes of BTC
GBC
Never smoker	18	8.4	1.00
Former smoker	23	11.5	1.20	0.64	2.26
Current smoker (<30 pack-years)	10	5.1	0.89	0.41	1.97
Current smoker (≥30 pack-years)	19	8.0	0.99	0.51	1.91
P-trend				0.771
EHBDC
Never smoker	40	18.8	1.00
Former smoker	39	19.6	0.83	0.53	1.31
Current smoker (<30 pack-years)	20	10.2	0.74	0.43	1.29
Current smoker (≥30 pack-years)	41	17.3	0.83	0.53	1.29
P-trend				0.400
AVC
Never smoker	5	2.3	1.00
Former smoker	6	3.0	1.24	0.37	4.13
Current smoker (<30 pack-years)	5	2.5	1.50	0.42	5.29
Current smoker (≥30 pack-years)	10	4.2	2.09	0.70	6.27
P-trend				0.160

AVC, ampulla of Vater cancer; CI, confidence interval; BTC, biliary tract cancer; 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.