title: Nocturnal and daytime esophageal acid exposure in normal-weight, overweight, and obese patients with reflux symptoms.
abstract: OBJECTIVE
  This study aimed to investigate the association between BMI and esophageal acid exposure in a cohort of patients referred for esophageal pH monitoring. The contributing roles of hiatal hernia, lower esophageal sphincter (LES) pressure, and intragastric pressure (IGP) were investigated, with an emphasis on reflux in the supine position.
  
  
  METHODS
  Esophageal manometry and 24-h pH-metry results were extracted from a prospectively collected database, and supplemental data (body mass, endoscopy results) from patient files.
  
  
  RESULTS
  In total, 245 patients (mean age 52.2±14 years, 54% men) were included in this study. In the normal-weight subgroup (n=87), the median acid exposure time was 1.1% [0-8.1] in the supine position (with interquartile range 25-75%) and 7.7% [2.5-14.8] in the upright position; the total acid exposure time was 7.4% [2.7-11.7]/24 h. In the overweight subgroup (n=104), the median acid exposure time was 4.9% [0.3-13.3] in the supine position and 11.1% [5.4-16.9] in the upright position; the total acid exposure time was 8.9% [4.7-15.8]/24 h. In the obesity subgroup (n=54), the median acid exposure time was 4.1% [0.7-14.3] in the supine position and 10.5% [5-17.5] in the upright position; the total acid exposure time was 8.3% [5.3-14.7]/24 h. Supine acid exposure was significantly higher in overweight and obese patients than in normal-weight patients (both P=0.02). In overweight patients, a hiatal hernia was predictive of supine and total acid exposure, as was a decreasing LES pressure in both the supine and the upright position. In obese patients, increased IGP contributed toward an increased total acid exposure. Although an association between increasing BMI and acid exposure was observed, BMI was not independently predictive.
  
  
  CONCLUSIONS
  Overweight and obesity is associated with increased reflux, especially in the supine position. The most important factors that contribute toward reflux are the presence of a hiatal hernia and a lower LES pressure in overweight patients and an increased IGP in obese patients.
authors.affiliation: aDepartment of Gastroenterology and Hepatology, University Medical Center Utrecht, Utrecht bDepartment of Gastroenterology and Hepatology, Slingeland Hospital Doetinchem, Doetinchem cDepartment of Gastroenterology and Hepatology, Academic Medical Center, University of Amsterdam, Amsterdam dDutch Obesity Clinic Hilversum, Hilversum, The Netherlands.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Burgerhart
authors.forename: Paul C
authors.initials: PC
authors.lastname: van de Meeberg
authors.forename: Peter D
authors.initials: PD
authors.lastname: Siersema
authors.forename: André J P M
authors.initials: AJ
authors.lastname: Smout
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D002940:Circadian Rhythm; D049630:Esophageal Sphincter, Lower / Q000503:physiopathology; D050782:Esophageal pH Monitoring; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D006551:Hernia, Hiatal / Q000150:complications; D006801:Humans; D056865:Ideal Body Weight; D016014:Linear Models; D008297:Male; D008365:Manometry; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000150:complications* / Q000175:diagnosis; D050177:Overweight / Q000150:complications* / Q000175:diagnosis; D011237:Predictive Value of Tests; D011312:Pressure; D012189:Retrospective Studies; D012307:Risk Factors; D016683:Supine Position; D013997:Time Factors