Gastroesophageal reflux disease (GERD) is a condition that develops when reflux of stomach contents causes troublesome symptoms and complications, such as reflux esophagitits, hemorrhage, stricture, Barrett's esophagus, and adenocarcinoma (1). According to the Montreal workshop report, reflux esophagitis is defined endoscopically by visible breaks in the distal esophageal mucosa (1). In clinical practice, endoscopic esophagitis is seen in less than 50% of patients with typical GERD symptoms (2). Several recent endoscope-based studies have suggested that overall prevalence of reflux esophagitis in Western Europe and North America was around 10%-20% (3, 4). In contrast, GERD has traditionally been considered less common in Asia (5-7). However, more recent studies suggest that prevalence of GERD in Asia is increasing (3, 8). In Japan, the overall prevalence of reflux esophagitis among the adult population is roughly 10%-15% (9). Incidence of erosive esophagitis (EE) is also increasing in the Korean population (10-12). For example, prevalence of EE in subjects undergoing a routine check up was reported at around 2% in the early 1990s, and 5% in the late 1990s (4). In 2006, the prevalence of EE was found to be 8% (13). Incidence is expected to increase, not only due to developments in endoscopic examination and increasing awareness of the condition, but also because of changes in preference to a more westernized diet and lifestyle (4).

Up to now, many epidemiologic studies of EE, particularly those from Korea, have had a potential limitation, in that most did not fully represent population-based results. Subjects who attended personal annual medical check-ups had a higher income and higher educational level than average population (14, 15). Thus, the chance of selection bias exists.

Therefore, we attempted to estimate the prevalence of EE in Koreans, including those of low socio-economic status. Actually, the study population included subjects ≥ 40 yr of age who were Medicaid recipients and beneficiaries in the National Health Insurance Corporation. In addition, we attempted to investigate risk factors for EE among them.

In Korea, it is generally accepted that the nationwide prevalence of reflux esophagitis is lower than that in Western countries. However, recent studies have shown an increasing trend in the number of patients with reflux esophagitis (17, 18). In addition, EE is increasing in Asia (14). For example, it has increased from 3% in the late 1970s to 10%-15% in the late 1990s, as reported by a Japanese study of upper gastrointestinal endoscopies (19). In addition, it has increased from 3% in the early 1990s to 13% in 2000-2001, based on a Malaysian study (20). A recent large-scaled nationwide multicenter Korean study revealed that prevalence of EE in healthy subjects who had routine check-ups was 7.9% in Korea (n = 25,536) (13). In this study, endoscopic examination indicated that the overall prevalence of EE in Korean Medicaid recipients and beneficiaries over the age of 40 yr was 6.7%.

The Korean National Cancer Screening Program (NCSP) was initiated in 1999 for the purpose of reducing cancer-related mortality through early detection of most common cancers in Koreans through mass screening programs (21). The target five most common cancers, which are among the leading causes of death in Korea, include stomach cancer, breast cancer, cervical cancer, liver cancer, and colon cancer. In particular, the Korean government offers this cancer screening program for free to the general population who are over the age of 40 yr, including beneficiaries in the National Health Insurance Corporation, which is a kind of social security health system in Korea, as well as Medicaid recipients who are low income members of the Korean population (22).

Most epidemiologic studies on EE, particularly those from Korea, have not shown population-based results. Thus, the present study could be representative of the general Korean population who are over the age of 40 yr.

Although we did not evaluate the grade of minimal change in erosive esophagitis due to its flaw of low interobserver agreement, endoscopic evaluation showed that most of the subjects had mild grade EE with grade A. Mild degree of EE in this study might explain the lower prevalence of EE in Korea compared with other Asian countries, such as Japan (5). This difference among countries is observed in the distribution based on the LA classification of EE. In Korea, LA-A accounted for 71%, LA-B 28%, and LA-C plus LA-D 1% in this study, which differs from LA-C plus LA-D of 12% reported in Japan (23) and LA-C plus LA-D of 20% reported in Malaysia (20). These differences regarding prevalence and severity of EE in Asian populations are not easily explained, but may be a result of genetic background, diet, or Helicobacter pylori infection status (14).

In this study, we divided the subjects into two groups according to the presence of EE on upper endoscopy. Clinical features and endoscopic findings between the two groups were compared.

Based on several results from Asian studies, probable risk factors are presumed to be related to EE; age ≥ 60 yr old, male gender, obesity, especially BMI ≥ 25, H. pylori eradication history, smoking, alcohol consumption, and endoscopic findings of HH are shown to be significant risk factors (13, 24). In accordance with previous reports, this study revealed that old age, male sex, BMI ≥ 25, current smoking, alcohol consumption, fasting glucose level ≥ 126 mg/dL, and hiatal hernia were significant risk factors for EE. ESEM was not proven to be a significant risk factor in EE, although it was predominant in subjects with EE in comparison to those without EE.

Interestingly, a recent report from Korea suggests that EE might represent the disease spectrum of the metabolic syndrome showing significant relationship of EE to obesity, low HDL cholesterol, high triglyceride, high blood pressure, and elevated fasting glucose (4). In this study, BMI was not significantly different between subjects with EE and those without EE; however, the percentage of BMI ≥ 25 was found to be higher in subjects with EE than in those without EE. This suggests that obesity, one of the components of metabolic syndrome, is associated with EE.

With regard to endoscopic evaluation of EE, HH could be an important clue to diagnosis of GERD and it also implies possible progression to EE. Although this study did not ascertain the significance of ESEM in diagnosis of EE, ESEM may remain as an important endoscopic finding in Barrett's esophagus, one of the complications of EE. There was some limitation in this study. Because our study was a retrospective study, GERD-related symptoms, such as heartburn and acid regurgitation, were not investigated. Furthermore, lack of information on H. pylori eradication history failed to elucidate the relationship between H. pylori infection and EE.

In conclusion, the prevalence of EE was 6.7% in low socioeconomic Korean population, and it is close to that of recent reports in healthy individuals who voluntarily underwent personal annual medical check-ups. Risk factors for EE among them include old age, male sex, BMI ≥ 25, current smoking, alcohol consumption, fasting glucose level ≥ 126 mg/dL, and HH.