Gastric cancer risk in relation to tobacco use and alcohol drinking in Kerala, India - Karunagappally cohort study

Table 4 Gastric cancer risk in relation to cigarette smoking among men

	Person-years	Gastric cancer cases	RR	95%CI	P value1
Cigarettes smoked per day					0.212
Never	398841	57	1.0	Reference
Former	71488	18	1.4	0.8-2.3
≤ 14	357740	36	0.8	0.5-1.2
≥ 15	43325	3	0.6	0.2-2.1
Unknown	29327	2	0.6	0.1-2.5
Duration of cigarette smoking					> 0.5
Never	398841	57	1.0	Reference
1-14	212691	12	0.9	0.5-1.8
15-29	134583	14	0.8	0.4-1.5
30-44	72749	18	1.0	0.6-1.7
≥ 45	41727	13	0.9	0.5-1.8
Unknown	40129	2	0.4	0.1-1.7
Age at start of cigarette smoking					> 0.5
< 18	53786	6	0.8	0.3-1.9
18-22	193597	20	0.8	0.5-1.4
≥ 23	143035	13	0.7	0.4-1.3
Never	398841	57	1.0	Reference
Unknown	39974	2	0.0
Years since quitting cigarette smoking					0.109
Current smoker	390298	39	1.0	Reference
< 5	27180	7	2.0	0.9-4.3
5-9	18804	6	2.4	1.0-5.6
≥ 10	24089	5	1.4	0.5-3.5
Never	398841	57	1.3	0.9-2.0
Unknown	41508	2	0.5	0.1-2.0

¹The P for trend (those in unknown categories were excluded).