Jin-Hai Wang, Jin-Yan Luo, Lei Dong, Jun Gong, Department of Gastroenterology, Second Hospital of Xi’an Jiaotong University, Xi’an 710004, Shaanxi Province, China
Ming Tong, Department of Preventive Medicine, Medical College of Xi’an Jiaotong University, Xi’an 710061, Shaanxi Province, China
Correspondence to: Dr. Jin-Hai Wang, Department of Gastroenterology, Second Hospital of Xi’an Jiaotong University, Xi’an 710004, Shaanxi Province, China.  jinhaiwang@hotmail.com
Telephone: +86-29-7679290    Fax: +86-29-7231758
Received: 2003-11-21    Accepted: 2003-12-16

Abstract
AIM: Gastroesophageal reflux disease (GERD) is a common disorder in the Western population, but detailed population-based data in China are limited. The aim of this study was to understand the epidemiology of symptomatic gastroesophageal reflux (SGER) in adults of Xi’an, a northwestern city of China, and to explore the potential risk factors of GERD.

METHODS: Symptoms suggestive of GERD, functional dyspepsia (FD), irritable bowel syndrome (IBS), upper respiratory diseases and some potential risk factors were investigated in a face-to-face manner in a region-stratified random samples of 2 789 residents aged 18-70 years in Xi’an by using a standardized questionnaire.

RESULTS: With a response rate of 91.8%, the prevalence of SGER was 16.98% (95% CI, 14.2-18.92) in Xi’an adults, and no gender-related difference was observed (P>0.05). SGER was more common among subjects aged 30-70 years than in those aged 18-29 years (P<0.05). The prevalence of SGER in rural, urban and suburban subjects was 21.07%, 17.44% and 12.12%, respectively, and there was a significant difference between rural, urban and suburban regions (P<0.05). Compared with subjects without SGER, the prevalence of symptoms suggestive of FD and IBS, pneumonia, asthma, bronchitis, laryngitis, pharyngitis, chronic cough, wheeze, globus sensation, oral ulcer and snore was significantly increased in subjects with SGER (P<0.01). Heavy smoking (OR=4.94; CI, 3.70-6.61), heavy alcohol use (OR=2.85; CI, 1.67-4.49), peptic ulcer (OR=5.76; CI, 3.99-8.32), cerebral palsy (OR=3.97; CI, 1.97-8.00), abdominal operation (OR=2.69; CI, 1.75-4.13), obesity (OR=2.16; CI, 1.47-3.16), excessive food intake (OR=1.43; CI, 1.17-1.75), sweet food (OR=1.23; CI, 0.89-1.54), and consumption of coffee (OR=1.23; CI, 0.76-2.00) were independently associated with SGER. The episodes of GERD were commonly precipitated by dietary factors (66.05%), followed by body posture (26.54%), ill temper (23.72%), fatigue (22.32%) and stress (10.93%).

CONCLUSION: GERD is common in Xi’an’s adult population with a mild or moderate degree. The etiology and pathogenesis of GERD are probably associated with FD, IBS, and some respiratory, laryngopharyngeal and odontostological diseases or symptoms. Some lifestyles, diseases and dietary factors are the risk factors of GERD.

Wang JH, Luo JY, Dong L, Gong J, Tong M. Epidemiology of gastroesophageal reflux disease: A general population-based study in Xi’an of Northwest China. World J Gastroenterol  2004; 10(11): 1647-1651
http://www.wjgnet.com/1007-9327/10/1647.asp

INTRODUCTION
Gastroesophageal reflux disease (GERD) is a common disorder, and approximately 17-38% of adults in the Western population experienced heartburn and/or acid regurgitation, the main symptoms of GERD, at least once per week; with 4-9% having daily symptoms^[1-3]. Some patients with GERD would develop Barrett’s esophagus, intestinal metaplasia of esophageal mucosa that predisposes to adenocarcinoma of the esophagus^[4-8], which has increased rapidly since 1970s^[9,10]. Patients with esophageal carcinoma have been proved to have a low 5-year survival rate^[11,12] In addition to the risk of cancer, GERD is well recognized to be associated with some upper respiratory diseases, having an adverse impact on the quality of life, and the cost of long-term medical therapy is substantial. Therefore, it is of much importance to understand the prevalence of GERD and to identify the potential risk factors to prevent GERD and GERD- related diseases. As detailed population-based data on GERD in China are currently limited, we aimed in this study to estimate the prevalence of SGER in Xi’an adults, to determine the relationship between GERD and FD, IBS, and upper respiratory diseases, and to explore the risk factors of GERD.

MATERIALS AND METHODS
Subjects
Xi’an is a northwestren city of China, consisting of 7 administrative districts and 3 counties. Of the administrative districts 4 are in the urban region and 3 in the suburban region, and the counties are all in the rural region. Each district includes numerous neighboring communities including multiple residential areas, and each of the county covers several townships governing a number of villages. Based on the 1997 census data obtained from the local government and the proportion of population within the regions, we randomly selected one or more residential areas or villages in the urban, suburban and rural regions, respectively. Finally, a total of 2 789 subjects entered this survey, including 911 subjects from the urban region, 853 from the suburban region, and 1 025 from the rural region. The proportion of subjects in different regions was similar to that of Xi’an population (P>0.05), and the selected samples were matched for age and gender with Xi’an population (P>0.05).

Questionnaire
The questionnaire was designed on the basis of previous works from two university hospitals^[13], but modified to suit the local conditions. The modified version contained 8 fractions covering a total of 130 relative questions (items), of which 15 were specifically concerned with the frequency and severity of symptoms suggestive of GERD in the past years. Other questions included those concerning general condition of the subject (self-reported height and weight), the symptoms suggestive of functional dyspepsia (FD) and irritable bowel syndrome (IBS) in the past year, symptoms or history of respiratory, laryngopharyngeal, and odontostological diseases in the past year; history of illness and operation, personal habits (smoking, alcohol), and dietary habits.

Definitions
The following definitions for symptom categories and diseases were used. Only symptoms occurring in the past year before the interview were considered. (1) Heartburn: a burning pain or burning sensation behind the sternum in the chest. (2) Acid regurgitation: a bitter or sour-tasting fluid reflux into the throat or mouth. (3) Food regurgitation: eaten food reflux into the mouth. Heartburn, acid regurgitation, and food regurgitation were considered to be the main symptoms of GERD. Each of the typical symptoms was estimated according to its severity and frequency, which measured on a 4-score scale. The severity was assessed as follows: 0, none; 1, mild (could be ignored); 2, moderate (could not be ignored but did not affect lifestyle); 3, severe (affected lifestyle). The score of symptom frequency was estimated as follows: 0, none or less than one occasion per month on average; 1, several occasions (1 to3) a month; 2, several occasions (1 to 6) a week; 3, one or more than one occasions daily. Based on the scores of the severity and frequency of the main GERD symptoms, a total score (range, 0 to 18) of each subject was calculated. (4) SGER: subjects with a total score (St) no less than 3. (5) Chest pain: any pain or discomfort felt inside the chest more than once per month on average but not including any pain caused by diagnosed heart disease. (6) Dysphagial: a feeling that food stuck in the throat or chest more than one per month. (7) Symptoms suggestive of FD and IBS and symptoms of respiratory, laryngopharyngeal, and odontostological diseases: any of these symptoms presented more than once a week on average in the past year. (8) History of diseases or operations: any disease or operation diagnosed or performed in a hospital before the interview. (9) Alcohol use: taking 300 g of alcohol per month. (10) Heavy alcohol use: taking 210 g or more of alcohol per week. (11) Smoking status: defined as current smoking, current non-smoking, and heavy smoking (more than one pack a day). (12) Obesity: a body mass index ≧30 kg/m². (13) Coffee and special beverages: drinking more than one cup per day on average. (14) Dietary habits: taking special food more than one servings per day on average.

Training of interviewers
The team of interviewers was constituted mainly by medical students studying preventive medicine in our university, who were trained by the same two professors, one was a physician of gastroenterology and understood well the relative definitions, and the other was a specialist in preventive medicine and had rich experience in survey.

Assessment of feasibility
Before the actual study, a pilot study was conducted among 100 unselected outpatients attending our gastroenterological clinic, to test the appropriateness of the questionnaire and to familiarize the interviewers with the survey procedure and the definitions. The problems that the interviewers encountered during the pilot study were discussed and their solutions were provided accordingly.     

Survey design and response rate
According to the list of selected subjects and guiding by the members of residents or village’s committee, all subjects were interviewed face to face at their home by the interviewers. The completed questionnaires were checked and kept by same physician. The absent subjects were registered and two reminder interviews were conducted at weekly intervals. Finally, the survey was closed after 16 wk. Among the 2 789 selected subjects, 74 had moved away, 58 could not be interviewed due to their absence during the survey period, 6 died, and 91 explicitly refused to participate in the study. A total of 2 560 subjects were successfully interviewed within a period of 4 mo, resulting in a response rate of 91.8%. There was no difference between the responders and non-responders with respect to their age and gender (P>0.05), and the constitution of the non-responder in different regions was reasonably similar (P>0.05). Twenty-eight individuals were subsequently excluded from the analysis because of inadequately questionnaires. Data from 2 532 questionnaires were entered in a computer.

Statistical analysis
The questionnaires were coded for analysis, and the data were entered in a computer and analyzed by using DBASEⅢ software. The prevalence was derived with 95% confidence intervals (95%CI). Comparison of the data was performed using EP15.0 x² test. The odds ratios (OR) and 95% CI for each significant variable in the final model were calculated from the coefficients estimated in the logistic regression model. All P values were two-tailed, with the level of statistical significance specified at 0.05.

RESULTS
Main symptoms of GERD
The prevalence of heartburn for at least once monthly, weekly and daily episodes was 10.98% (278/2 532), 4.07% (103/2 532) and 1.66% (42/2 532), respectively. That for acid regurgitation monthly was 21.01%  (532/2 532), weekly 7.78% (197/2 532), and daily 3.53% (89/2 532). For food regurgitation, the prevalence was 8.57% (217/2 532), 3.28% (83/2 532), and 1.42% (36/2 532) for at least one occasion monthly, weekly, and daily, respectively.

Symptomatic gastroesophageal reflux
The distribution of the total score of main GERD symptoms in the responders is shown in Table 1. The prevalence of SGER was 16.98% (95%CI, 14.20-18.92), of which, 13.11%, 2.92%, and 0.95% were considered as mild, moderate, and severe, respectively.  Responders with SGER were more likely to be a mild or moderate degree. 

Table 1  The distribution of total score of main GERD symptoms of responders (n=2 532)  

Relationship between SGER and gender, age, and region
There was no statistically significant difference between men and women in the prevalence of GERD (61.71% vs 17.25%, P>0.05), and the ratio of male/female was 1:1.03. The prevalence of SGED was relatively constant across each of 10-year age interval (Table 2, x² for trend; P= 0.075), but by cutting x² apart, we found that the prevalence of GERD was significantly higher in the responders aged 30-70 years than in those aged 18-29 years (x²=4.40, P<0.05), and the group aged 50-59 years had the highest prevalence of SGEG (21.39%). The responders in the urban and rural regions were more likely than the responders in suburban regions to have SGER (21.07% and 17.44% vs 12.12%, P<0.05). However, SGER was similarly prevalent in the urban and rural regions (P>0.05).

Table 2  The prevalence of SGED in each age group  

Association between SGER and respiratory, laryngopharyngeal, and odontostoloical diseases
Table 3 summarized the prevalence of some respiratory, laryngopharyngeal, and odontostological diseases or symptoms in responders with and without SGER. The responders with SGER reported a higher prevalence of pneumonia, asthma, bronchitis, pharyngitis, laryngitis, chronic cough, wheeze, globus sensation, oral ulcer, and snore than the responders without SGER.

Table 3  The prevalence of respiratory, laryngopharyngeal, and odontostological diseases or symptoms in responders with and without SGER  

Relationship between SGER and other common gastrointestinal symptoms
The prevalence rate of pain behind the sternum, dysphagia, retching, nausea, vomiting, epigastric discomfort, epigastric fullness, epigastric pain, diarrhoea, and constipation in responders with SGER was significantly higher than that in the responders without SGER (P<0.01, Table 4).

Table 4  Other common gastrointestinal symptoms in responders with and without GERD