Introduction Western populations have recently experienced a substantial rise in both obesity and gastro-oesophageal reflux disease (GORD). There is growing evidence of a link between both conditions with higher BMI associated with greater prevalence of GORD symptoms, Barrett's oesophagus and oesophageal adenocarcinoma. Currently, the most common dyspeptic patients seen in clinical practice are H pylori negative with a normal endoscopy. It is unclear if BMI has any effect on oesophageal physiology in these patients.

Aims To examine the association between BMI and the function of the lower oesophageal sphincter (LOS) in dyspeptic patients with a normal endoscopy.

Methods Patients with dyspepsia, a normal endoscopy and negative for H pylori had their BMI measured followed by assessment with water perfused oesophageal manometry and 24-h oesophageal pH monitoring. The LOS pressure, LOS length and LOS intra-abdominal length (high pressure zone distal to respiratory inversion point) were measured by station pull through. This involved withdrawing the catheter at 1 cm increments every minute with the patients sitting. Pressures were expressed using intragastric pressure as baseline. 24-h oesophageal acid exposure was measured as the per cent time pH <4 for the total, upright and supine period. Association between BMI and each of the above parameters was assessed using Spearman Rank Correlation (SR).

Results 105 patients (46 males) were studied (mean age 44 years range 20–74). The median BMI was 26 (range 17.6–40.4) with 39% overweight and 20% obese. Higher BMI was associated with higher oesophageal per cent time pH <4 for total (SR=0. 43, p≤0.001), upright (SR=0.33, p=0.001) and supine (SR=0.37, p≤0.001,) periods and was also associated with a lower resting LOS pressure (SR=−0.32, p=0.002). LOS length (SR=−0.02, p=0.82) and LOS intra-abdominal length (SR=−0.18, p=0.09) were not significantly associated with BMI.

Conclusion In patients with normal endoscopy there is a strong association between BMI and impaired function of the gastro-oesophageal barrier. The mechanism of this association requires to be investigated.