Effect of smoking on the risk of gastrointestinal cancer after cholecystectomy: A national population-based cohort study

Table 4 Subgroup analysis according to smoking status and quantity in patients who underwent cholecystectomy

Variables		Colorectal cancer						Gastric cancer
		Age			Sex			Age			Sex
			IR1	Adjusted HR (95%CI)		IR1	Adjusted HR (95%CI)		IR1	Adjusted HR (95%CI)		IR1	Adjusted HR (95%CI)
Smoking status	Non-smoker	< 65 years	0.96	1 (Ref.)	Male	1.82	1 (Ref.)	< 65 years	0.58	1 (Ref.)	Male	2.06	1 (Ref.)
	Ex-smoker		1.32	1.27 (0.97-1.65)		2.22	1.35 (1.13-1.62)		1.13	1.11 (0.84-1.46)		2.20	1.21 (1.02-1.44)
	Current smoker		0.95	1.14 (0.87-1.49)		1.52	1.45 (1.18-1.79)		1.01	1.36 (1.03-1.80)		1.66	1.44 (1.18-1.76)
	Non-smoker	≥ 65 years	2.62	1 (Ref.)	Female	1.32	1 (Ref.)	≥ 65 years	2.12	1 (Ref.)	Female	0.68	1 (Ref.)
	Ex-smoker		4.20	1.39 (1.12-1.73)		1.09	1.14 (0.59-2.21)		4.45	1.19 (0.97-1.47)		0.48	1.06 (0.39-2.86)
	Current smoker		5.36	1.87 (1.44-2.42)		1.56	1.72 (1.11-2.67)		4.90	1.37 (1.05-1.78)		0.28	0.67 (0.25-1.82)
Smoking quantity	Non-smoker	< 65 years	0.96	1 (Ref.)	Male	1.82	1 (Ref.)	< 65 years	0.58	1 (Ref.)	Male	2.06	1 (Ref.)
	0 < pack-years < 10		0.85	1.18 (0.87-1.60)		1.35	1.29 (1.01-1.65)		0.67	1.13 (0.80-1.59)		1.29	1.11 (0.86-1.42)
	10 ≤ pack-years < 20		0.87	1.02 (0.73-1.42)		1.43	1.24 (0.98-1.58)		0.85	1.09 (0.77-1.53)		1.37	1.08 (0.85-1.37)
	20 ≤ pack-years < 30		1.11	1.14 (0.79-1.62)		1.94	1.40 (1.10-1.78)		1.16	1.24 (0.87-1.78)		2.16	1.42 (1.12-1.78)
	30 ≤ pack-years		2.03	1.50 (1.10-2.04)		2.97	1.52 (1.25-1.86)		2.06	1.43 (1.05-1.95)		3.16	1.45 (1.19-1.75)
	Non-smoker	≥ 65 years	2.62	1 (Ref.)	Female	1.32	1 (Ref.)	≥ 65 years	2.12	1 (Ref.)	Female	0.68	1 (Ref.)
	0 < pack-years < 10		4.07	1.40 (1.01-1.93)		1.06	1.27 (0.78-2.08)		3.81	1.09 (0.79-1.52)		0.31	0.83 (0.34-2.03)
	10 ≤ pack-years < 20		4.16	1.45 (1.06-1.99)		1.02	0.91 (0.34-2.44)		3.77	1.06 (0.77-1.46)		0.51	0.94 (0.23-3.80)
	20 ≤ pack-years < 30		5.10	1.71 (1.26-2.34)		2.83	2.33 (0.87-6.25)		5.56	1.50 (1.12-2.01)		0
	30 ≤ pack-years		4.75	1.57 (1.22-2.02)		6.76	4.57 (2.03-10.28)		4.98	1.30 (1.02-1.65)		1.11	1.42 (0.20-10.12)

¹Per 1000 person-years.

Hazard ratio was adjusted for age, sex, alcohol consumption, regular physical activity, hypertension, diabetes mellitus, dyslipidemia, body mass index, and estimated glomerular filtration rate. IR: Incidence rate; HR: Hazard ratio.