Obesity and gastroesophageal reflux: quantifying the association between body mass index, esophageal acid exposure, and lower esophageal sphincter status in a large series of patients with reflux symptoms

Abstract

Introduction: Obesity and gastroesophageal reflux disease (GERD) are increasingly important health problems. Previous studies of the relationship between obesity and GERD focus on indirect manifestations of GERD. Little is known about the association between obesity and objectively measured esophageal acid exposure. The aim of this study is to quantify the relationship between body mass index (BMI) and 24-h esophageal pH measurements and the status of the lower esophageal sphincter (LES) in patients with reflux symptoms.

Methods: Data of 1,659 patients (50% male, mean age 51 +/- 14) referred for assessment of GERD symptoms between 1998 and 2008 were analyzed. These subjects underwent 24-h pH monitoring off medication and esophageal manometry. The relationship of BMI to 24-h esophageal pH measurements and LES status was studied using linear regression and multiple regression analysis. The difference of each acid exposure component was also assessed among four BMI subgroups (underweight, normal weight, overweight, and obese) using analysis of variance and covariance.

Results: Increasing BMI was positively correlated with increasing esophageal acid exposure (adjusted R (2) = 0.13 for the composite pH score). The prevalence of a defective LES was higher in patients with higher BMI (p < 0.0001). Compared to patients with normal weight, obese patients are more than twice as likely to have a mechanically defective LES [OR = 2.12(1.63-2.75)].

Conclusion: An increase in body mass index is associated with an increase in esophageal acid exposure, whether BMI was examined as a continuous or as a categorical variable; 13% of the variation in esophageal acid exposure may be attributable to variation in BMI.

Figure 1

Composite pH score (mean, SE) across BMI groups. A significant difference between all BMI groups was observed (p < 0.0001, ANOVA). Post hoc tests used to calculate the statistical significance of differences between each two adjacent individual BMI groups.

Figure 2

Prevalence of a defective LES across BMI groups (p < 0.0001, chi-square test).

Figure 3

Interaction between LES resting pressure, BMI, and esophageal acid exposure in all subjects (n = 1659).

Figure 4

Interaction between LES status, BMI, and esophageal acid exposure in all subjects (n = 1659). LES status stratified on an ordinal scale of 0–3, according to the number of LES components (resting pressure and total and abdominal length) within the normal range: 0 all components defective, 1 only one component normal, 2 two components normal, 3 all three components normal.