Body mass index, long-term weight change,and esophageal squamous cell: Carcinoma is the inverse association modified by smoking status?

BACKGROUND: Observational studies suggest that body mass index (BMI) is inversely associated with esophageal squamous cell carcinoma (ESCC). However, questions remain regarding reverse causation and confounding, especially by smoking, as alternative explanations. METHODS: The authors examined the association between BMI and measures of weight history and risk of ESCC in a population-based Australian case-control study (from 2002 to 2005) comprising 287 patients with ESCC (cases) and a control group of 1544 individuals who were sampled from a population registry. Stratified analyses were performed specifically to explore whether this association was influenced by smoking. Multivariable logistic regression models were used to derive odds ratios (ORs). RESULTS: After adjusting for smoking, significant inverse associations with ESCC for BMI and weight 1 year before diagnosis, maximum adult BMI, and weight gain since age 20 years were observed (all Ptrend <.001). The risk of ESCC was reduced by 35% (range, 23%-44%) per 5-unit increase in recent BMI. Participants who gained weight after age 20 years had a lower risk than those who maintained their weight during adult life (OR for gain of >20 kg, 0.51; 95% confidence interval [CI], 0.33-0.77). In stratified analyses, higher BMI was associated with a decreasing risk of ESCC both in never-smokers (OR, 0.32; 95% CI 0.13-0.76) and smokers (OR 0.22, 95%CI 0.07-0.67) comparing the highest versus the lowest BMI quintile. CONCLUSIONS: In this study, the inverse associations between BMI, long-term weight gain, and other body measures and ESCC appeared to be robust and could not be explained by smoking status or potential confounding factors. © 2011 American Cancer Society.