title: Body mass index, long-term weight change, and esophageal squamous cell carcinoma: is the inverse association modified by smoking status?
abstract: 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 P(trend) < .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.
authors.affiliation: Queensland Institute of Medical Research, Cancer and Population Studies, Brisbane, Australia. petra.lahmann@qimr.edu.au
authors.forename: Petra H
authors.initials: PH
authors.lastname: Lahmann
authors.forename: Nirmala
authors.initials: N
authors.lastname: Pandeya
authors.forename: Penelope M
authors.initials: PM
authors.lastname: Webb
authors.forename: Adèle C
authors.initials: AC
authors.lastname: Green
authors.forename: David C
authors.initials: DC
authors.lastname: Whiteman
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia / Q000453:epidemiology; D015992:Body Mass Index; D002294:Carcinoma, Squamous Cell / Q000209:etiology*; D016022:Case-Control Studies; D004938:Esophageal Neoplasms / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking; D015430:Weight Gain; D015431:Weight Loss