Lifestyle and risk of stomach cancer: A hospital-based case-control study

Background. Stomach cancer (SC) is the most frequent cancer among males and third most common cancer among females in Madras, India. The incidence rate of SC is higher in Southern India compared to Northern India. Methods. A hospital-based case-control study on 388 incident cases of SC was carried out in Madras as part of a multicentre study in India to identify the risk factors for SC. Cases were matched to cancer controls based on age (+/- 5 years), sex, religion and mother tongue. Categorical variables for income group, level of education and area of residence were included in all models to control for confounding. Results. Smokers had a twofold risk of SC (95% confidence interval [CI] = 1.25-3.78) compared to non smokers and the risk seen among current smokers (odds ratio [OR] = 2.5: 95% CI:1.36-4.44) was significantly different from that seen among exsmokers (OR = 1.5; 95% CI:0.67-3.54). The risk among those who smoke bidi (OR = 3.2; 95% CI:1.80-5.67) was higher than that seen among cigarette (OR = 2.0; 95% CI:1.07-3.58) and chutta (OR = 2.4; 95% CI:1.18-4.93) smokers. Significant dose response relationships were observed with age began smoking bidi (P < 0.001) and with lifetime exposure to bidi (P < 0.001), cigarette (P < 0.01) and chutta (P < 0.05) smoking. The habits of drinking alcohol and chewing did not emerge as risk factors. An interaction effect was not seen between the lifestyle habits. Attributable risk (AR) for smoking among exsmokers was 33% and current smokers 60%. Population AR for smoking was 31%. Conclusion. Smoking tobacco is an independent risk factor for SC.