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

Table 1 Sociodemographic features of study subjects (men) and their associations with gastric cancer

	n	Person-years	Gastric cancer cases	RR	95%CI	P value
Total	65553	900721
Religion						> 0.52
Hindu	47689	658303	88	1.0	Reference
Muslim	11841	160475	19	0.9	0.5-1.5
Christian	6023	81942	9	0.8	0.4-1.6
Family income3						0.1911
< 500	4367	66066	10	1.1	0.6-2.2
501-1200	19460	281461	41	1.0
1201-2500	24794	332258	37	0.7	0.5-1.1
2501-3500	10839	141566	14	0.6	0.3-1.0
3500+	6093	79370	14	1.0	0.5-1.8
Education						0.1641
Illiterate	4143	52337	7	0.5	0.2-1.1
Primary school	16917	221434	49	1.0	Reference
Middle school	17310	238947	30	0.7	0.5-1.2
High school	20775	298699	25	0.7	0.4-1.1
College	5703	79877	4	0.4	0.1-1.1
Unknown	705	9427	1	0.5	0.1-3.9
Occupation						0.0082
Farmers and fishermen	21683	302651	51	1.0	Reference
Skilled workers	12445	169094	21	0.8	0.5-1.3
White collars	13672	183094	28	0.8	0.5-1.2
Others	17753	245882	16	0.4	0.2-0.7

¹The P for trend;

²The P for heterogeneity;

³Monthly family income in Indian National Rupee (INR). One INR is approximately 0.016 US dollars. In the analysis examining the relation between socioeconomic status and gastric cancer risk, a relative risk was obtained from the following model: H = H_s exp (B_iX_i), where the background hazard, H_s, was stratified by attained age and calendar time, and X_i denotes categorical variables of the sociodemographic factors shown in the table.

Table 2 Gastric cancer risk in relation to tobacco use and alcohol drinking among men

	n	Person-years	Gastric cancer cases	RR	95%CI	P value1
Total	65553	900721
Bidi smoking						0.042
Never	31277	441290	35	1.0	Reference
Former	5830	70584	15	1.3	0.7-2.5
Current	25403	347383	62	1.6	1.0-2.5
Unknown	3043	41464	4	1.0	0.4-3.0
Cigarette smoking						0.265
Never	29205	398841	57	1.0	Reference
Former	5603	71488	18	1.4	0.8-2.4
Current	27835	390298	39	0.8	0.5-1.2
Unknown	2910	40093	2	0.4	0.1-1.7
Tobacco chewing						> 0.5
Never	42190	582656	73	1.0	Reference
Former	4383	54094	9	0.8	0.4-1.6
Current	18568	258317	34	0.9	0.6-1.4
Unknown	412	5653	0
Alcohol drinking						0.175
Never	33296	454553	51	1.0	Reference
Former	7857	98248	16	0.9	0.5-1.7
Current	24399	347905	49	1.3	0.9-2.0
Unknown	1	14	0

¹The P for trend (those in unknown categories were excluded). The model used for statistical analysis to obtain the RRs associated with tobacco and alcohol use was as follows: H = H_s exp(B_iX_i), where the background hazard, Hs, was stratified by attained age, calendar time, occupation and education, and X_i denotes categorical variables related to tobacco and alcohol use. Similar models were used in the analysis that produced the results presented in Tables 3-5.

Table 3 Gastric cancer risk in relation to bidi smoking among men

	Person-years	Gastric cancer cases	RR	95%CI	P value1
Bidis smoked per day					0.012
Never	441290	35	1.0	Reference
Former	70584	15	1.3	0.7-2.5
1-4	40768	4	1.0	0.4-2.8
5-14	131494	20	1.4	0.8-2.5
15-24	105359	23	1.9	1.1-3.4
≥ 25	67303	15	1.7	0.9-3.2
Unknown	43924	4	1.0	0.3-2.8
Duration of bidi smoking					0.036
Never	441290	35	1.0	Reference
1-14	141330	10	1.3	0.6-2.8
15-29	123435	14	1.1	0.6-2.1
30-44	84545	30	2.0	1.2-3.5
≥ 45	68393	23	1.6	0.9-3.0
Unknown	41728	4	1.0	0.4-3.0
Age at start of bidi smoking					0.161
< 18	64800	14	2.0	1.0-3.9
18-22	172714	32	1.8	1.1-2.9
≥ 23	109709	16	1.3	0.7-2.5
Never	441290	35	1.0	Reference
Unknown	41624	4	0.0
Years since quitting bidi smoking					0.424
Current smokers	347383	62	1.0	Reference
< 5	28435	6	0.9	0.4-2.0
5-9	18058	5	1.1	0.5-2.9
≥ 10	23055	4	0.6	0.2-1.7
Never	441290	35	0.6	0.4-1.0
Unknown	42500	4	0.6	0.2-1.7

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

Table 5 Gastric cancer risk in relation to alcohol drinking among men

	Person-years	Gastric cancer cases	RR	95%CI	P value
Type of alcohol
Never drinker	454152	51	1.0	Reference	> 0.51
Former drinker	98248	16	0.9	0.5-1.7
Toddy	10404	3	2.3	0.7-7.3
Arrack	60956	12	1.7	0.9-3.3
Foreign	63835	7	1.4	0.6-3.3
Combination	209740	27	1.2	0.7-1.9
Other	3384	0	0.0
Duration of alcohol consumption					> 0.52
Never	454553	51	1.0	Reference
1-14	148811	14	1.8	1.0-3.3
15-29	176222	19	1.0	0.5-1.6
30-44	71460	26	1.4	0.9-2.3
≥ 45	11079	1	0.3	0.0-2.5
Unknown	38596	5	1.3	0.5-3.2
Age at start of alcohol drinking					0.1792
< 25	146010	15	1.0	0.5-1.7
≥ 25	166508	29	1.6	1.0-2.6
Never	454553	51	1.0	Reference
Unknown	35400	5	1.5	0.6-3.7

¹The P for heterogeneity;

²The P for trend (those in unknown categories were excluded).

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).