AIM: To investigate the incidence of gastroesophageal reflux disease (GERD) and its related risk factors in Uygur and Han Chinese adult in Urumqi, China.

METHODS: A population-based cross-sectional survey was undertaken in a total of 972 Uygur (684 male and 288 female) aged from 24 to 61 and 1023 Han Chinese (752 male and 271 female) aged from 23 to 63 years. All participants were recruited from the residents who visited hospital for health examination from November 2011 to May 2012. Each participant signed an informed consent and completed a GERD questionnaire (Gerd Q) and a lifestyle-food frequency questionnaire survey. Participants whose Gerd Q score was ≥ 8 and met one of the following requirements would be enrolled into this research: (1) being diagnosed with erosive esophagitis (EE) or Barrett’s esophagus (BE) by endoscopy; (2) negative manifestation under endoscopy (non-erosive reflux disease, NERD) with abnormal acid reflux revealed by 24-h esophageal pH monitoring; and (3) suffering from typical heartburn and regurgitation with positive result of proton pump inhibitor test.

RESULTS: According to Gerd Q scoring criteria, 340 cases of Uygur and 286 cases of Han Chinese were defined as GERD. GERD incidence in Uygur was significantly higher than in Han Chinese (35% vs 28%, χ² = 11.09, P < 0.005), Gerd Q score in Uygur was higher than in Han Chinese (7.85 ± 3.1 vs 7.15 ± 2.9, P < 0.005), and Gerd Q total score in Uygur male was higher than in female (8.15 ± 2.8 vs 6.85 ± 2.5, P < 0.005). According to normalized methods, 304 (31%) cases of Uygur were diagnosed with GERD, including 89 cases of EE, 185 cases of NERD and 30 cases of BE; 256 (25%) cases of Han Chinese were diagnosed with GERD, including 90 cases of EE, 140 cases of NERD and 26 cases of BE. GERD incidence in Uygur was significantly higher than in Han Chinese (31% vs 25%, χ² = 9.34, P < 0.005) while the incidences were higher in males of both groups than in females (26% vs 5% in Uygur, χ² = 35.95, P < 0.005, and 19.8% vs 5.2% in Han, χ² = 5.48, P < 0.025). GERD incidence in Uygur male was higher than in Han Chinese male (26% vs 19.8%, χ² = 16.51, P < 0.005), and incidence of NERD in Uygur was higher than in Han Chinese (χ² = 10.06, P < 0.005). Occupation (r = 0.623), gender (r = 0.839), smoking (r = 0.322), strong tea (r = 0.658), alcohol drinking (r = 0.696), meat-based diet (mainly meat) (r = 0.676) and body mass index (BMI) (r = 0.567) were linearly correlated with GERD in Uygur (r = 0.833, P = 0.000); while gender (r = 0.957), age (r = 0.016), occupation (r = 0.482), strong tea (r = 1.124), alcohol drinking (r = 0.558), meat diet (r = 0.591) and BMI (r = 0.246) were linearly correlated with GERD in Han Chinese (r = 0.786, P = 0.01). There was no significant difference between Gerd Q scoring and three normalized methods for the diagnosis of GERD.

CONCLUSION: GERD is highly prevalent in adult in Urumqi, especially in Uygur. Male, civil servant, smoking, strong tea, alcohol drinking, meat diet and BMI are risk factors correlated to GERD.

Gastroesophageal reflux disease (GERD) is a common acid-related disease worldwide, and severely affects the quality of life of patients. The incidence of GERD is high in Western and developed countries, however, due to changes in lifestyle and dietary habits the incidence of GERD has increased in the Asian-Pacific region in recent years[1,2], particularly in China. This is due to the introduction of Western fast food into the Chinese dietary structure which has had a significant influence since its introduction ten years ago. The incidence of GERD in China is rising year by year[3], and is showing a “low in south and high in north” trend[4]. Xinjiang is located in the Northwest region of China, and Uygur is the main minority group in this autonomous region of China. An important dietary custom in local residents is to prioritize meat (mainly beef and lamb), cooked wheaten food, and alcohol drinking. In addition, strong tasting foods are favored. Together with the development of social and cultural diversity, there appears to have been culture blendings and interactions between Uygur and Han Chinese as time goes by. In addition to these factors, the particular geographic and climatic characteristics of Xinjiang exert an influence on the lifestyle and dietary customs of local inhabitants. Therefore, there are currently both similarities and differences between Uygur and Han Chinese with regard to lifestyle and dietary customs. Furthermore, genetics studies have revealed that the Han Chinese gene contains Oriental Mongoloid characteristics, while the Uygur gene contains both Caucasian and Oriental Mongoloid characteristics. To our knowledge, there has been little research focusing on the incidence of GERD with regard to minority groups[5], and large-scale studies focusing on GERD in the Uygur population alone have not been carried out. Based on the above research background, we aimed to elucidate the following: (1) Does lifestyle and dietary customs or dietary structure in Xinjiang inhabitants impact on GERD occurrence; (2) differences in the incidence of GERD in Uygur and Han Chinese; and (3) potential risk factors related to GERD, and provide guidance in clinical practice.

GERD is a chronic disorder which has a significant impact on quality of life, and consumes a large number of medical resources worldwide. The incidence of GERD is higher than ever, particularly in Asian countries and China. Many publications on GERD have focused on southern China, however, there are few reports which have focused on northern China or minority groups. Therefore, the purpose of our large-scale, population-based investigation was to determine whether lifestyle and dietary customs of the local residents in Xinjiang play a role in GERD, whether the incidence of GERD is different between Uygur and Han Chinese, and which risk factors can lead to GERD.

By applying normalized methods (upper gastrointestinal endoscopy, 24-h esophageal pH monitoring and the PPI test), a total of 304 Uygur (31%) and 256 Han (25%) participants were classified as having GERD, 61% had NERD, 29% had EE and 10% had BE in the Uygur GERD group (254 male and 50 female), and in the Han group (203 male and 53 female), 55% had NERD, 35% had EE and 10% had BE. The incidence of GERD in Uygur was significantly higher than that in Han Chinese adults. The results of the present investigation also showed that the incidence of GERD in both Uygur and Han male adults was higher than that in Uygur and Han female adults, respectively. In addition, the incidence of NERD in Uygur was higher than that in Han. Using stratification analysis, we found that in Uygur with GERD, civil servant ratio, strong tea ratio, alcohol drinking ratio and BMI value in males were higher than those in normal males and females, respectively. The civil servant ratio, alcohol drinking ratio and BMI value in Uygur females with GERD were higher than those in normal females. In Han with GERD, the same results as those described in Uygur were observed, however, the mainly meat ratio in both males and females with GERD was higher than that in normal males and females. Regression analysis further revealed a correlation between seven factors and GERD in Uygur and Han participants, respectively. The above results indicated the presence of ethnic and gender differences between Uygur and Han Chinese with regard to GERD in China. The correlation between occupation, alcohol drinking as well as BMI and GERD was similar to previous studies[12-14]. A recent study found that the incidence of GERD in Caucasians was higher than that in other ethnic groups, which suggested that Caucasian was a related factor[15]. Anthropology research has demonstrated that the gene structure in Uygur subjects contains Caucasian and Mongolian bloodlines[16,17], thus the gene fusion characteristics in Uygur may reasonably explain their different phenotype with regard to GERD, which is not only different from but also similar to that of Han Chinese. The mainly meat ratio in both male and female Han participants with GERD was higher than that in normal males and females, respectively, and may be an independent risk factor associated with GERD. Although we cannot explain this result in Han at present, further research is needed in order to determine whether this result is objective, and whether ethnic groups or gene polymorphisms are related to GERD occurrence[18,19].

It has been shown that there are geographic and population (gender, age, ethnic group) differences in the incidence of GERD[20]. Related GERD etiological factors include BMI, smoking, alcohol consumption, esophageal hiatus, and inheritance. GERD may also be associated with chronic cough, asthma, pharyngitis, stomatitis and sleep disorder[12]. In the present study, the incidence of GERD in Han was higher than that found in several previous reports[3,4], and was possibly due to environmental differences. To date, there have been no published reports on GERD in Uygur, our findings showed that the incidence of GERD in Uygur (including NERD) was significantly higher than that in Han. In addition, the incidence of GERD in Uygur was higher than that in Israeli subjects, while the GERD ratio in females was lower than those in Israeli and Japanese females[21,22]. However, our findings were in agreement with those in previous studies carried out in Western populations, which indicated a ethnic group difference [23], further highlighting ethnic group and geographical differences.

The Gerd Q was designed by Jones et al[8] in 2007, and was used to assess and diagnose GERD, and to assess symptom changes and quality of life in GERD patients. Several studies have demonstrated its effectiveness and reliability[24]. Receiver operating characteristic curve analysis revealed that when taking a score of 8 as the diagnostic threshold for GERD, the accuracy rating was up to 70%, which was close to the diagnostic level of a gastroenterologist. After comparing the diagnostic rate for GERD, we found that there was no significant difference between the normalized methods and the Gerd Q scale, thus a Gerd Q score of ≥ 8 can be used as a standard to diagnose GERD. Since more than 50% of GERD patients have NERD, it is impracticable to diagnose GERD routinely using endoscopy or 24-h esophageal pH monitoring in China. Therefore, in the case of a young or middle-aged patient intolerant of invasive examination who has typical reflux symptoms, but no warning symptoms, a diagnostic method based on symptoms may be desirable. We suggest that the Gerd Q scale may be used as a primary clinical diagnostic approach[25,26].

The backward method of logistic regression analysis revealed that gender, occupation, strong tea, alcohol drinking, mainly meat and BMI were the six common related risk factors in Uygur and Han adults with GERD; for Uygur adults with GERD, smoking was a related risk factor which was different from that in Han, and for Han, age was a related risk factor which was different from that in Uygur. Furthermore, all factors correlated with GERD in a linear manner. Because the age of 75% of the participants in this investigation ranged from 35 to 45 years, we did not analyze the relationship between age stratification and GERD, however, the results revealed a gender difference (Table 4). Gender, smoking and alcohol drinking have been demonstrated to be risk factors for GERD[12]. Smoking was not shown to correlate with GERD in Han participants. The smoking ratio which was lower in Han than in Uygur and racial difference were the main risk factors, in addition to occupation related to GERD in Han. This may have been due to the nature of work, lifestyle, and less exercise in Han. The above results confirmed the correlation between these risk factors and GERD. We suggest that males and civil servants are susceptible to GERD. A recent study demonstrated that gender was a related factor for GERD in Japan[27], and our results are consistent with these findings.

Xinjiang is located in Northwest China, and is a multi-ethnic area, where the day is longer than the night, and cold and dry conditions are the main climatic features which are different from those inland, and dinner-to-bed time is shorter than that inland. A recent report indicated that shorter dinner-to-bed time was significantly associated with an increased OR for GERD[28]. Uygur is the main minority group in Urumqi, and the ethnic culture, religion, lifestyle and dietary customs are different from those in Han, as mainly meat (beef and lamb) and dairy products are important dietary components. Han Chinese who live in the same region have many similarities to Uygur subjects with the exception of differences such as meat and milky tea (milky tea is a conventional drink in Uygur). The dietary structure of residents in Xinjiang is characterized by high caloric, high fat, spicy, strong flavors, strong tea, smoking and alcohol drinking which are more prevalent in males; in addition, changing lifestyle, obesity prevalence, as well as changing population structure have increasingly led to transition of the disease spectrum, which has become and is becoming common and an important etiology of GERD in Uygur and Han Chinese. Drinking strong tea is a common traditional custom in Uygur and Han subjects in Xinjiang, Fu-Brick tea which the Uygur drink and the various teas which the Han drink are fermentative green teas. Green tea consumption has also been shown to be negatively associated with the risk of chronic atrophic gastritis, as green tea can suppress the proliferation of Helicobacter pylori in the stomach and inhibit the progression of chronic atrophic gastritis[29]. Therefore, green tea, especially strong green tea, can increase gastric acid secretion leading to the development of GERD symptoms. Thus, we consider green tea to be a significant risk factor for GERD[10].

In conclusion, the present investigation and logistic regression analysis with regard to GERD in a large population clearly demonstrated that GERD is highly prevalent in adults living in Urumqi. The incidence of GERD in Uygur and Han adults, especially Uygur, was similar to that in Western populations. There are ethnic group and gender differences between Uygur and Han, and regional differences between China’s Xinjiang residents and other countries. Being male, smoking, alcohol drinking, strong tea, mainly meat and BMI are the main risk factors for GERD in Uygur, while being male, civil servant, alcohol drinking, strong tea, mainly meat and BMI are the main risk factors for GERD in Han. These factors have a significant impact on GERD symptoms and quality of life. Our results also demonstrated that the Gerd Q can be used to diagnose GERD and possibly allow the evaluation of clinical efficacy in GERD patients.

Based on the above results, it would be very advantageous to prevent the development of GERD and cure it by optimizing lifestyle (such as controlling weight[30], aerobic exercise, avoid overeating, appropriate sleep)[31], modifying dietary structure (low caloric intake, low fat intake, avoid strong and spicy foods, more vegetables, high cellulose, less stimulating beverages, less smoking, less alcohol drinking), and reducing foods and drugs that probably lead to a fall in lower esophageal sphincter pressure. When suffering from GERD symptoms, one should consult a doctor and undergo appropriate treatment under the guidance of the doctor.