Background: Despite the importance of gastroesophageal reflux disease (GERD) for patients and society, large studies using objective tests of reflux to determine risk factors for this disease have not been reported. This study aimed to identify these factors using the presence of abnormal esophageal acid exposure on pH monitoring to define GERD.Methods1147 patients with symptoms suggestive of GERD who had undergone prolonged ambulatory esophageal pH testing in this department were studied. Patients with a history of any foregut operation except cholecystectomy and patients with a named esophageal motility disorder were excluded. Tobacco and alcohol information was obtained from a standard questionnaire. Patients with a pH less than 4.0 for >4.4% of the test period were considered to have GERD. A 1cm station pull-through method was used for lower esophageal sphincter (LES) measurements. The statistical analysis used contingency tables, the Mantel-Haenszel test, smoothed plots of the proportion of GERD and the log-odds of GERD, and univariate logistic regression. 70% and 30% parts of the data were randomly selected to construct a model for both the demographic and the full (demographic plus pathophysiological data) regressions.ResultsUnivariate analysis restricted to demographic factors found that highly significant demographic risk factors for GERD were male sex, white non-Hispanic ethnic group, greater age, height, weight, and body mass index, and history of current or past tobacco smoking. Alcohol intake >20g per day was significantly associated with an increased risk of GERD. Highly significant pathophysiological risk factors were lower LES resting pressure, lower total LES length, and lower intra-abdominal LES length. Antral Helicobacter pylori infection was significantly inversely associated with a diagnosis of GERD. On multivariate logistic regression analysis, factors that remained significantly associated with an increased risk of GERD were, in order of statistical significance: 1. Lower LES pressure 2. Heavier weight 3. Tobacco smoking 4. Overweight and obesity 5. Older age 6. Short total LES length 7. No antral H pylori infection.ConclusionsSignificant risk factors for GERD include overweight and obesity. GERD risk factors are similar to known risk factors for Barrett's esophagus and Barrett's adenocarcinoma. These two conclusions have important public health implications for many Western societies. The presence of a mechanically defective lower esophageal sphincter was most strongly associated with the objective diagnosis of GERD on esophageal pH testing.