Sex differences in the relation between waist circumference within the normal range and development of reflux esophagitis

We examined the association of abdominal obesity and waist circumference within normal range with the incidence of reflux esophagitis, separately in men and women. This cohort study involved 142,679 Korean adults without reflux esophagitis, who underwent upper endoscopy at baseline and during follow-up. Waist circumference was categorized into the following quartiles: <80, 80.1–85, 85.1–90, and ≥90.1 cm in men; and <69.3, 69.3–74, 74.1–79.5, and ≥79.6 cm in women. During the 551,877.8 person-years of follow-up, 29,509 participants developed reflux esophagitis. The association between waist circumference quartiles and risk of reflux esophagitis significantly differed with sex (p for interaction < 0.001). In men, multivariable-adjusted hazard ratios (HRs) (95% confidence intervals (CIs)) comparing waist circumference quartiles 2, 3, and 4 to the lowest quartile were 1.03 (0.99–1.07), 1.08 (1.04–1.12), and 1.15 (1.10–1.19), respectively. In women, HRs (95% CIs) comparing quartiles 1, 2, and 4 to the 3rd quartile were 1.10 (1.04–1.17), 1.03 (0.98–1.10), and 1.07 (1.01–1.13), respectively. In this large cohort with endoscopic follow-up, the risk of reflux esophagitis increased with increasing waist circumference even within the normal range in men, whereas the risk increased with low normal waist circumference or with abdominal obesity in women, indicating a U-shaped association.