Background: Obesity has been associated with GERD, however the mechanism by which obesity may cause GERD is unclear. The association between esophageal acid exposure and total body or abdominal anthropometric measures has not been examined.
Methods: We conducted a cross-sectional study of consecutive patients undergoing 24 hour pH-metry. Standardized measurements of body weight, height as well as waist and hip circumference were obtained. The association between several parameters of esophageal acid exposures and anthropometric measures were examined in univariate and multivariate analyses.
Results: We enrolled 206 patients (63% women) who were not on acid suppressing medications with a mean age of 51.4 years. BMI>30 (compared to BMI<25) was associated with a significant increase in acid reflux episodes, long reflux episodes (> 5 minutes), time with pH<4, as well as a calculated summary score. These significant associations have affected total, postprandial, upright and supine pH measurements. The Waist circumference was also associated with esophageal acid exposure but not as significant or consistent as BMI. When adjusted for waist circumference by including it in the same model, the association between BMI>30 and measures of esophageal acid exposure became attenuated for all, and not significant for some thus indicating that waist circumference may mediate a large part of the effect of obesity on esophageal acid exposure.
Conclusions: Obesity increases the risk of GERD at least partly by increasing esophageal acid exposure. Waist circumference partly explains the association between obesity and esophageal acid exposure.