Gastroesophageal reflux does not alter effects of body mass index on risk of esophageal adenocarcinoma

• Background & Aims: A history of high body mass index (BMI) is strongly associated with risk of esophageal adenocarcinoma (EAC). We investigated whether gastroesophageal reflux is involved in this association. Methods: We analyzed data from a population-based Swedish nationwide study of patients with a new diagnosis of EAC (n=189) or gastroesophageal junction adenocarcinoma (n= 262), and matched controls (n=816), from 1995 through 1997. Our analysis included data on BMI 20 y before study inclusion; maximum adult BMI; frequency, severity and duration of gastroesophageal reflux symptoms; tumor features; and covariates (sex, age, smoking, alcohol, fruit and vegetables intake, and socio-economic status). We conducted stratified analyses and synergy tests, adjusting for covariates. Results: Odds ratios (ORs) for EAC among subjects with BMI ≥25 20 y before inclusion, compared with those with BMI <25, did not differ significantly, without or with adjustment for gastroesophageal reflux frequency (OR, 3.1; 95% confidence interval [CI], 2.2–4.4 and OR, 3.3; 95% CI, 2.2–4.8), severity (OR, 3.3; 95% CI, 2.2–4.8), or duration (OR, 3.2; 95% CI, 2.2–4.7). However, there were strong interactions and synergisms between BMI and gastroesophageal reflux categories. BMI appeared to have the largest effect on gastroesophageal reflux frequency (synergy index 8.9; 95% CI, 2.3–34.1 for maximum BMI and gastroesophageal reflux >3 times weekly). Conclusions: Based on a population-based study, the association between BMI and EAC does not appear to be affected by symptomatic gastroesophageal reflux, although BMI and reflux act synergistically.

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