Abstract 632: Effect of body mass index on the association between smoking and risk of gastric cancer in the Singapore Chinese Health Study
Authors: Koh Woon-Puay , Jin Aizhen , Yuan Jian-Min 
Published: August 2012

Abstract
Background: Tobacco smoking is an established risk factor for gastric cancer. Recently, reports have suggested high body mass index (BMI) as a significant risk factor for esophageal adenocarcinoma whereas the relationship with gastric cancer remains inconsistent. The aim of the current study is to evaluate two potentially modifiable factors, tobacco smoking and increased body mass index, as risk factors for gastric cancer among Singapore Chinese. Methods: We prospectively examined the association between smoking and BMI at baseline, and the risk of developing gastric cancer in the Singapore Chinese Health Study, a cohort of 63,257 middle-aged and older Chinese men and women enrolled between 1993 and 1998. Information on body weight, height, cigarette smoking and other lifestyle factors and diet was obtained through in-person interview at enrollment. BMI was calculated using weight in kg divided by height in meter squared (kg/m2). Incidence of cancer and death among cohort participants was obtained via linkage with nationwide registries. Results: As of 31 December 2009, 568 cohort participants who were free of cancer at baseline had developed gastric cancer. Compared to never smokers, current smokers had a 38% increase in risk of gastric cancer (95% confidence interval: 1.12-1.70), with a positive dose-response association between number of cigarettes per day (P for trend=0.002) and number of years of smoking (P for trend=0.005), and gastric cancer risk. After adjustment for cigarette smoking and other potential confounders, hazard ratios (95% confidence interval) of gastric cancer for subjects with BMI 20-&lt;24, 24-&lt;28 and 28+ kg/m2 were 1.30 (1.00-1.68), 1.19 (0.88-1.60), and 1.65 (1.14-2.40), respectively, relative to those with &lt;20 kg/m2 (P for trend=0.063). This dose-response association between increasing BMI and cancer risk was stronger for cardia cancer (P for trend =0.021) than for noncardia cancer (P for trend=0.19). In separate analyses in groups defined by BMI, hazard ratios (95% confidence interval) of gastric cancer for current smokers with BMI of β28, 24-&lt;28, 20-&lt;24, and &lt;20 kg/m2 were 1.11 (0.51-2.45), 1.08 (0.67-1.75), 1.52 (1.16-1.99), and 1.90 (1.05-3.43), respectively, as compared with nonsmokers. The positive dose-response associations between dose and duration of smoking, and gastric cancer risk were limited to lean subjects with BMI&lt;24 kg/m2 and not observed in the more obese subjects. Conclusion: Smokers with relatively low level of BMI had enhanced risk of gastric cancer compared to smokers with higher BMI. Our findings corroborate the hypothesis that lean smokers have increased oxidative DNA damage relative to their non-lean counterparts, which may in turn explain their heightened susceptibility to tobacco carcinogens-induced DNA damage in gastric carcinogenesis.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 632. doi:1538-7445.AM2012-632