Gastroesophageal reflux disease (GERD) has for a long time been considered a distinctly uncommon disease among Asians. In an early paper by Kang et al., a low prevalence of reflux esophagitis of 3.3% was reported.1 However, at the turn of the millennium, several review papers were published in this journal and others commenting on the rising incidence of GERD in the Asian population.2–5 In clinical practice, GERD and its complications have been encountered more frequently and this has culminated in the 1st Asian Pacific consensus report in 2005.6
Papers published in recent years have shown a higher prevalence of erosive esophagitis ranging from 6.1 to 15%7–11 compared to earlier studies. Similarly, surveys on the prevalence of GERD symptoms in the community have also shown a higher prevalence ranging from 9 to 17%12–16 compared to older studies. A time trend study from Singapore tracked the rising prevalence of esophagitis in endoscopy records from 1992 to 2001.17 From the same group, a revisit to a previously surveyed community in Jurong, Singapore showed a higher prevalence of GERD symptoms of 9.9% in 1999 compared to 1.6% in 1994.18
Further evidence for the increasing prevalence of reflux esophagitis is published in this issue of the Journal with the report of a large number of patients who underwent endoscopy in a major medical center in the Philippines. Sollano et al. reported a significant increase in the prevalence of erosive esophagitis, from 2.9% in 1994–1997 to 6.3% in the period of 2000–2003.19 The authors discussed the possible reasons for this increase; they include a decrease in H. pylori infection, which the authors have documented earlier in their own center, over the same period of time.20 A change in dietary intake, specifically an increase in dietary fat had been suggested and an increase in smoking and drinking alcohol was inferred from Philippine national statistics on smoking and drinking. However, as the study was essentially a retrospective review, data on obesity and the BMI of patients were not available.
This is unfortunate, as among the factors that have been postulated as underlying this dramatic change in the prevalence of GERD in Asia, obesity is perhaps the most important. In this same issue of the Journal, Kang et al. report that obesity is an independent predictive factor for reflux esophagitis.21 In their single-center study from Seoul, Korea, Kang and colleagues carried out a prospective cross-sectional study on a large group of patients who attended health screening; they correlated abdominal obesity and body mass index (BMI) with reflux symptoms and endoscopic esophagitis. The prevalence of reflux symptoms in this study was 8.2% and esophagitis was 6.6%. The authors found that the prevalence of esophagitis increased with increasing BMI up to a prevalence of 16% in the group with BMI greater than 30 kg/m2. When predictive factors for esophagitis and reflux symptoms were tested with a multiple logistic regression analysis model, abdominal obesity came out as an independent significant factor for esophagitis but not for reflux symptoms.
Symptoms of reflux have always been difficult to assess. Although the authors used a validated questionnaire, ‘GERD’ as a disease entity is fairly ‘new’ to Asian patients compared to peptic ulcer disease, for example. In clinical practice, Asian patients often do not understand what heartburn is, having no such word in the local vernacular language. The use of a locally validated questionnaire for Asians, for example the one used in Hong Kong, China, as opposed to the one used in this study, which was constructed and based on a western population, may have given a different outcome to the analysis.22
BMI, as defined, was also not a significant independent factor for both esophagitis and reflux symptoms. Kang et al. used the World Health Organization (WHO) definition of BMI which, again, is based on a Western population.23 Increasingly, however, studies in Asian patients have used a modification of this criterion as proposed by the Western Pacific Regional Office of the WHO, which allows for the smaller bone structure and different adipose distribution of Asian patients and thus gives a more accurate reflection of the body fat stores.24 That Asians in general, appear slim and are therefore not overweight may be a false perception based on a smaller body frame; Asian studies should make use of this modified BMI criteria. Obesity has become a major problem among Asians. Two recent surveys from China showed that overweight and obesity affected a significant proportion of the population.25,26 Obesity and its attendant associated diseases such as cardiovascular disease, diabetes mellitus and non-alcoholic fatty liver have been reported to be on the increase in the Asia–Pacific region.27–29
For many years, the proposal that obesity is a cause/risk factor of GERD has been bandied about and many textbooks of medicine have included obesity as a risk factor for GERD. As a corollary, many doctors tell their patients to lose weight as a treatment for GERD. Among the plausible mechanism(s) of disease causation, increased intra-abdominal pressure, impaired gastric emptying, decreased lower esophageal sphincter tone and an increase in the number of transient lower esophageal sphincter relaxations have been demonstrated in obese subjects.30–33 A recent study by Pandolfino and colleagues used sophisticated manometry techniques to show an increase in intragastric pressure as well as gastroesophageal pressure gradients in obese individuals.34 Both these pathophysiological mechanisms would increase the reflux of gastric contents into the lower esophagus.
In a meta-analysis of published studies, Hampel and colleagues have shown that obesity is associated with increased reflux symptoms, erosive esophagitis and esophageal adenocarcinoma.35 However, this review was based exclusively on Western data. Data on Asian patients have been sparse. Rosaida and Goh, in a prospective cross-sectional study, reported on overweight (defined as BM > 25 kg/m2) as an independent significant risk factor for GERD overall as well as for non-erosive reflux disease, but not for reflux esophagitis.9
GERD is clearly a fast-emerging disease in the Asia–Pacific region. Although statistics vary and better quality studies are needed, consistently higher figures for both prevalence of reflux symptoms and reflux esophagitis point to a true increase in the disease. The dramatic increase in disease prevalence in a relatively short space of time points to putative environmental factors. The common denominating factor throughout the entire region is the marked socioeconomic development. Specific factors are difficult to identify but it is obvious that obesity is an undesirable side-effect of a ‘better’ lifestyle in the entire Asian region and is likely to play a major role in the increase of GERD in Asia.