The Effects of Obesity on Oesophageal Function, Acid Exposure and the Symptoms of Gastro-Oesophageal Reflux Disease

R. Anggiansah; R. Sweis; A. Anggiansah; T. Wong; D. Cooper; M. Fox

Disclosures

Aliment Pharmacol Ther. 2013;37(5):555-563. 

In This Article

Abstract and Introduction

Abstract

Background Obese patients have an increased risk of gastro-oesophageal reflux disease; however, the mechanism underlying this association is uncertain.

Aim To test the hypothesis that mechanical effects of obesity on oesophageal function increase acid exposure and symptoms.

Methods Height, weight and waist circumference (WC) were measured in patients with typical reflux symptoms referred for manometry and 24 h ambulatory pH studies. Symptom severity was assessed by questionnaire. The association between obesity [WC, body mass index (BMI)], oesophageal function, acid exposure and reflux symptoms was assessed.

Results Physiological measurements were obtained from 582 patients (median age 48, 56% female) of whom 406 (70%) completed symptom questionnaires. The prevalence of general obesity was greater in women (BMI ≥ 30 kg/m2; F 23%:M 16%; P = 0.056), however more men had abdominal obesity (WC ≥ 99 cm (M 41%:F 28%; P = 0.001)). Oesophageal acid exposure increased with obesity (WC:R = 0.284, P < 0.001) and was associated also with lower oesophageal sphincter (LOS) pressure, reduced abdominal LOS length and peristaltic dysfunction (all P < 0.001). Univariable regression showed a negative association of WC with both LOS pressure and abdominal LOS length (R = −0.221 and −0.209 respectively; both P < 0.001). However, multivariable analysis demonstrated that the effects of increasing WC on oesophageal function do not explain increased acid reflux in obese patients. Instead, independent effects of obesity and oesophageal dysfunction on acid exposure were present. Reflux symptoms increased with acid exposure (R = 0.300; P < 0.001) and this association explained increased symptom severity in obese patients.

Conclusions Abdominal obesity (waist circumference) is associated with oesophageal dysfunction, increased acid exposure and reflux symptoms; however, this analysis does not support the mechanical hypothesis that the effects of obesity on oesophageal function are the cause of increased acid exposure in obese patients.

Introduction

Gastro-oesophageal reflux disease (GERD) is common in the community and reflux symptoms impact on quality of life.[1] The prevalence of GERD is increasing and this is thought to be linked to the global rise in obesity.[2–6] This trend is of concern also because of the significant link between a history of reflux symptoms and the risk of developing Barrett's oesophagus and oesophageal adenocarcinoma;[7] a link that is most evident in obese, elderly male patients.[8–10]

There is a strong, positive association between obesity and GERD in clinical studies. Obese patients have increased numbers of reflux events and oesophageal acid exposure on pH studies[11–13] and an increased risk of erosive oesophagitis on endoscopy.[14–18] There is also an association between obesity and reflux symptoms; although this is not a consistent finding in all patient groups with discordant results reported in men and women and in different racial groups.[6,17–20]

Abdominal obesity may be of particular relevance for GERD. Waist circumference (WC) rather than body mass index (BMI) is the anthropomorphic measure of obesity that best predicts the presence of erosive oesophagitis and reflux symptoms.[6] Physiological studies have shown that WC increases intra-gastric pressure and gastro-oesophageal pressure gradient and is associated with anatomical disruption of the oesophago-gastric junction (OGJ).[21,22] Moreover, increasing intra-gastric pressure by tightening a belt around the abdomen in healthy subjects produces similar changes to the OGJ as those seen in obesity.[23] These findings suggest that mechanical effects of abdominal obesity promote gastro-oesophageal reflux.[21–23] However, recent observations have suggested that other mechanisms, including the release of metabolic and humoral mediators from visceral adipose tissue, may provide a better explanation for the link between obesity and GERD.[17,19,24] Thus, it remains uncertain to what extent mechanical effects of abdominal adiposity explain the association between obesity and GERD.

This analysis tests the 'mechanical hypothesis' that abdominal obesity disrupts the structure and function of the OGJ reflux barrier and applies statistical techniques to assess if this effect impacts on the severity of oesophageal acid exposure and reflux symptoms. Demographic, anthropometric, physiological and clinical measurements were obtained from a large cohort of patients referred for oesophageal investigations. Univariable and multivariable regression were performed to test whether the effects of abdominal adiposity (WC) or general obesity (BMI) on oesophageal function best explain the increase in oesophageal acid exposure and reflux symptoms seen in this patient group.

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