Prevalence of gastro-oesophageal reflux disease
The prevalence of GORD and its complications is thought to be higher in the West ( Table 1) 4,7,8,18–24 than in Asia ( Table 2). 1,2,24–33 In Asia, few studies on the prevalence of GORD and its complications have been made. Few reports were published before the 1980s and those that exist indicate considerably lower levels of GORD than in the West. 1,32 Similarly, a low prevalence of hiatal hernia 25 and of Barrett’s oesophagus 34,35 has been recorded in Asians.
Table 1. Prevalence of gastro-oesophageal reflux disease (GORD),* its associated complications and its symptoms in North America and Europe
|Heartburn||20–40% of adult population; 4|
| ||14% reporting symptoms|
| || weekly, 7% reporting|
| || symptoms daily 18|
|Barrett’s oesophagus||10–15% of GORD patients 4|
|Hiatal hernia||50% of GORD patients;|
| ||16–22% of general population 7,8|
|Non-cardiac chest pain||Up to 50% of cases attributable|
| || to GORD 19|
|Oesophageal stricture||1% of GORD patients 20|
|Delayed gastric emptying||20–40% of GORD patients 21,22|
|Reflux oesophagitis||7–23% of GORD patients 23|
Table 2. Prevalence of gastro-oesophageal reflux disease (GORD)* and associated complications in Asian studies
|Burkitt and James 25||Asia||1973||< 2% frequency of hiatal hernia in radiographic examinations|
|Ke et al.26||China||1993||83% of 52 non-cardiac chest-pain patients diagnosed with GORD|
|Lau et al.27||Hong Kong||1996||29% of 108 non-cardiac chest-pain patients diagnosed with GORD|
|Hu et al.28||Hong Kong||1997||5% of 1558 ethnic Chinese assessed by questionnaire had GORD|
|Lee et al.29||Korea||1994||3% prevalence of oesophagitis|
|Yeom et al.30||Korea||1998||5% of 1010 patients assessed by endoscopy had reflux oesophagitis and 4% had|
| || || ||hiatal hernia|
|Kang et al.31||Singapore||1993||3% prevalence of endoscopic oesophagitis in > 10 000 patients|
|Wang et al.32||Taiwan||1978||9% of 165 patients assessed by endoscopy had mucosal injury|
|Chen et al.1||Taiwan||1979||2% of 1000 patients assessed by endoscopy had erosive oesophagitis|
|Chang et al.33||Taiwan||1997||17% of 2044 patients recorded one GORD symptom, 5% had reflux oesophagitis,|
| || || || 2% had hiatal hernia|
|Yeh et al.2||Taiwan||1997||15% of 464 patients assessed by endoscopy had erosive oesophagitis, 2% had|
| || || || Barrett’s oesophagus and 7% had hiatal hernia|
More recent studies suggest that the prevalence of GORD in Asia is either increasing or being recognized more frequently. In Hong Kong, Lau et al. classified almost 30% of patients with non-cardiac chest pain as having GORD by using 24 h ambulatory pH monitoring to measure abnormal reflux patterns. 27 In the West, the proportion of non-cardiac, chest-pain patients with GORD has been reported at higher levels (as high as 50%) 19 but other Western studies 36 have produced similar results to those of Lau et al. In a study conducted in China in 1993, Ke et al. found a very high prevalence of GORD (83%) in patients with non-cardiac chest pain; 26 those investigators used a combination of oesophageal function tests, which could explain the very high rates of GORD. However, Hu et al. showed that only 5% of a Chinese population had GORD; 28 this rate is considerably lower than equivalent reports from the West. 37
In a 1-year study in Taiwan, patients evaluated for upper gastrointestinal tract symptoms had a prevalence of erosive oesophagitis (15%) similar to that recorded in the West. 2 Barrett’s oesophagus was also found in numbers similar to Western reports (2% of the overall study population and 14% of those with oesophagitis). The prevalence of hiatal hernia (7% overall and 29% in patients with erosive oesophagitis) was lower than in Western studies but the method of detection of hiatal hernia can influence significantly the apparent prevalence (e.g. data from barium swallow methods are lacking in Asia). No conclusions were drawn from that study about the overall prevalence of GORD because endoscopy alone was used, without 24 h oesophageal pH monitoring.
In a large study of Taiwanese patients, 17% had at least one of three reflux symptoms (acid regurgitation, heartburn and belching) almost daily. 33 This prevalence confirmed that symptoms of GORD are common among the Chinese. However, endoscopy showed that reflux oesophagitis, with a prevalence of 5%, was less common than in the West and less than reported by Yeh et al.2 Hiatal hernia rates were low in the whole study group and were observed in only 20% of patients with oesophagitis; this is significantly lower than in the West.
In Korea, reflux oesophagitis was found in 5% of patients referred for upper gastrointestinal endoscopy. 30 Although lower than in Western reports, this is higher than the 3% prevalence among Koreans reported previously. 29 The difference may be because the study involved a tertiary medical centre to which only patients with more severe symptoms were referred. The prevalence of hiatal hernia was also higher than expected (32% of patients with reflux oesophagitis). A low frequency of oesophagitis (3%) was found in patients with upper gastrointestinal complaints in Singapore; this study involved 10 000 patients. 31
Delayed gastric emptying occurs in approximately 20–40% of GORD patients in the West 21,22 but has been recorded in up to 50% of patients. 6 In a small-scale study in China, Hou et al. found delayed gastric emptying in a similar proportion of GORD patients (54%). 38
Factors relating to prevalence of gastro-oesophageal reflux disease in Asia
Several factors that influence the prevalence of GORD have been identified ( Table 3). 33,39–45 Differences in these factors are often used to explain the lower prevalence of GORD in Asia but little supportive evidence exists. The reasons for the recent increase in the prevalence of GORD in Asia are also not clear; this increase may be apparent rather than real. In the West, increased medical attention to GORD, improved diagnosis and technological advances led to more patients being diagnosed with GORD. Thus, in Asia, increased referrals for symptoms of GORD, improved diagnosis and an increase in the use of endoscopy may be contributing to the apparent increase in prevalence.
Table 3. Possible factors contributing to the lower prevalence of gastro-oesophageal reflux disease in Asia than in the West 33,39–45
|Low maximal acid output/small parietal cell mass|
|High lower oesophageal sphincter pressure|
|Lower body mass index and lower obesity|
|Lower consumption of alcohol, coffee and tea|
|Fewer aggravating medicines used|
|Lower dietary fat/chocolate|
|Lower consumption of carbonated soft drinks|
|Lower consumption of citrus fruit drinks|
In a prospective study of Malaysian patients with dyspepsia attending a primary care clinic, 46 heartburn and acid regurgitation were reported by 58 and 50% of patients, respectively. However, few of these patients reported severe symptoms (4% with heartburn; 2% with regurgitation) and the prevalence of oesophagitis, detected by endoscopy, was low. 47 This suggests that mild (endoscopy-negative) GORD is quite prevalent in the Malaysian population.
Diet may be one of the major reasons for lower rates of GORD in Asia. In general, food and drink can make GORD worse because both fill the stomach, induce transient relaxations of the lower oesophageal sphincter and stimulate gastric acid production. However, specific dietary components are a more likely cause of differences between the West and Asia.
Dietary fat has been shown to increase the frequency of transient lower oesophageal sphincter relaxations, 39,48 possibly via release of cholecystokinin. 49 Therefore, the lower fat content of Asian diets may explain, in part, the lower prevalence of GORD. In addition, the increase in GORD in Asia appears to correlate with an increase in dietary fat. Department of Health data from Taiwan showed that dietary fat in Taiwan increased from 11 g/day per person in 1945 to 81 g/day per person in 1978 and 137 g/day per person in 1991. 2 The fat content of chocolate may explain the reported precipitation of GORD symptoms by chocolate.
Another dietary cause of heartburn is acidic drinks. 40 The prevalence of GORD in Asia may be related to the consumption of citrus fruit drinks or carbonated soft drinks (which have very low pH) but no evidence indicates that Asians drink fewer of these drinks than Westerners or that an increase in consumption has contributed to the increase in GORD in recent years.
Other factors that may contribute to the difference in the prevalence of GORD between Asia and the West include cigarette smoking, alcohol consumption, obesity and body mass index. Smoking can increase the risk of GORD by causing transient reduction in lower oesophageal sphincter pressure, reducing salivary output and increasing acid clearance time. 41 The consumption of alcohol may increase the occurrence of GORD by inducing oesophageal motor dysfunction. 42 However, little evidence indicates that smoking or alcohol intake is lower in Asia than in the West or that they have increased in line with the prevalence of GORD.
Obesity has been reported to be associated with hiatal hernia and oesophagitis; 50 therefore, lower rates of obesity (and smaller body mass index) in Asians may contribute to the lower prevalence of GORD and its complications. For example, Chang et al. reported that body mass index was significantly higher in Chinese patients with oesophagitis than in those without oesophagitis. 33
Genetic differences may also account for the contrast between the West and Asia. Higher parietal cell mass in the stomach (resulting in higher gastric acid secretion) has been observed in people with a higher body mass index (i.e. those in the West). Another often overlooked factor is the difference in the maximal acid output between races. Lower rates of maximal and basal acid output have been reported in Indians and Chinese than in Europeans and Americans. 43,51,52 The investigators took into account the lower body mass index in Asians and still found significant differences in maximal acid output. The reason for these differences is not clear but the lower maximal acid output could explain why fewer Asian than Western patients with GORD experience chest pain. 27 Maximal and basal acid output have increased in Japan in the past 20 years but the causative factor is unknown. 53
Widespread H. pylori eradication may also contribute towards increased gastric acid in some patients. In the West, H. pylori infections are decreasing, with a concomitant decrease in peptic ulcer prevalence and this correlates with an increased prevalence of GORD. 54 In Japan, patients with H. pylori infection tended to have decreased gastric acid secretion, possibly because H. pylori infection may contribute to atrophic gastritis, 53,55,56 but the increases in maximal and basal acid output in these patients in the past 20 years was independent of H. pylori. 53 The link between H. pylori eradication and the development of GORD is still in doubt and, therefore, less extensive use of H. pylori eradication therapy in Asia is unlikely to be responsible for lower rates of GORD.
In a recent Korean study, 57 relatively high lower oesophageal sphincter pressures were found even in patients with reflux oesophagitis. The authors suggested that this could contribute to the lower rates of GORD in Korea.
Certain medicines, such as opioid analgesics, anticholinergic agents and calcium antagonists can aggravate reflux. These medications may previously have been used less frequently in Asia but their use appears to be increasing (no evidence to confirm this has been published). Non-steroidal anti-inflammatory drugs are known to induce gastrointestinal damage, such as peptic ulcers, and recent reports also suggest that these drugs can induce GORD or reflux-like symptoms. 58 The data are sparse but certain medicines may contribute to the observed increase in the prevalence of GORD in the elderly. 2,44 Alternatively, the combined effect of ageing and aggravating medicines may decrease lower oesophageal sphincter pressure or oesophageal acid clearance. 2 Hence, lower rates of GORD in Asia may reflect younger populations and recent increases in GORD may be the result of improved life expectancy. The evidence for this is rather weak and, in recent Asian studies, no link was shown between prevalence of reflux oesophagitis and patient age. 30,33
Drinks such as tea and coffee have been linked to GORD but this is also contentious. Although tea has been shown to increase gastric acid secretion, 45 it does not appear to contribute to GORD. By comparison, coffee apparently increases gastro-oesophageal reflux. 59 The irritant effect of coffee may be caused by its higher caffeine content but this has been disputed. 59 Coffee is relatively unpopular in Asia and this could contribute to the lower prevalence of GORD, although no evidence indicates that coffee consumption is on the increase. Chang et al. found no link between coffee or tea consumption and the incidence of oesophagitis. 33
The mechanisms by which many of the above factors influence the rate of GORD are not known and the reasons for the historically lower prevalence of GORD in Asia and the increase in its prevalence in recent years are not clear. Although some form of westernization is often given as the reason for the increase, insufficient evidence exists to reach a firm conclusion. The increase in the prevalence of GORD in Asia has predictably led to a greater need for accurate diagnosis and rapid treatment of symptoms.