Original article
Alimentary tract
Nonlinear Relationship Between Body Mass Index and Esophageal Acid Exposure in the Extraesophageal Manifestations of Reflux

https://doi.org/10.1016/j.cgh.2011.12.032Get rights and content

Background & Aims

Obesity is believed to be an important etiologic factor in gastroesophageal reflux disease. However, it is not clear how obesity might affect esophageal acid exposure in patients with extraesophageal manifestations of reflux.

Methods

We conducted a cross-sectional study of 223 patients with extraesophageal symptoms suspected of being related to reflux. Participants underwent endoscopy and 48-hour wireless pH testing. The percentage of time at a pH of less than 4 (total, upright, and supine) was measured for each patient, and data were compared with corresponding body mass index (BMI), as continuous and categoric variables (normal, 18.5 to <25; overweight, 25 to <30; and obese, >30). Multivariable linear regression was used to identify variables associated with percentage of total time at a pH less than 4. The primary predictor of interest was BMI; age, sex, esophagitis, and hiatal hernia status were considered potential confounders or precision variables.

Results

Esophageal acid exposure was associated significantly (P < .001) with BMI. The percentage of time at a pH less than 4 and total symptomatic reflux events increased significantly (P = .005) with increasing BMI. The relationship between percentage of time at a pH less than 4 and BMI was nonlinear and S-shaped. With BMI ranges, the percentage of time at a pH less than 4 increased by 0.23% (normal BMI), 0.75% (overweight), and 0.07% (obese) for every 1-kg/m2 increase in BMI (P < .001).

Conclusions

Increases in esophageal acid exposure are greatest among overweight patients and plateau in obese patients. The findings have implications for benefit of weight loss in patients with suspected extraesophageal manifestations of gastroesophageal reflux disease.

Section snippets

Materials and Methods

The study was performed in accordance with the Declaration of Helsinki, and good clinical practice and applicable regulatory requirements. The Vanderbilt Institutional Review Board approved this clinical trial (IRB #090814).

Demographics and Body Mass Index Distribution

The study population consisted of 223 patients (median age, 53 y; interquartile range [IQR], 42–61 y; 76% female; 91% Caucasian; median BMI, 28; IQR, 24–32). The primary symptom complaints included the following: cough (52%), asthma (19%), hoarseness (15%), sore throat (6%), sinusitis/rhinitis (5%), and globus (3%). A secondary complaint of heartburn and/or regurgitation was present in 40% of patients. Hiatal hernia was present in 28% of patients (80% with <2 cm). Esophagitis was present in 15%

Discussion

This study objectively assessed the relationship between BMI and GERD in patients suspected of having extraesophageal manifestations of reflux. Similar to prior reports in patients with typical GERD,7, 8, 10, 20, 21 we found that esophageal acid exposure increased significantly with increasing BMI as a continuous as well as categoric variable. However, our data suggest that the increase in acid exposure per unit increase in BMI is not linear, unlike as previously reported in typical GERD. The

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    Conflicts of interest The authors disclose no conflicts.

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