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Keywords:

  • colorectal cancer;
  • gastric cancer;
  • gastroesophageal reflux disease;
  • Helicobacter pylori;
  • peptic ulcer disease;
  • time trends

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

The new millennium has seen distinct changes in the pattern of gastrointestinal disease in the Asia–Pacific region. These changes are important as more than half of the world's population come from the region and therefore impact significantly on the global disease burden. The highest incidence of gastric cancer (GCA) has been reported from Asia and GCA remains a very important cancer. However time-trend studies have shown a decrease in GCA incidence in several countries in Asia. A rise in cardio-esophageal cancers as seen in the West has not been reported. On the other hand, colorectal cancer has been steadily increasing in Asia with age-standardized incidence rates of some countries approaching that of the West. The pattern of acid-related diseases has also changed. Gastroesophageal reflux disease is a fast emerging disease with an increasing prevalence of reflux esophagitis and reflux symptoms. The prevalence of peptic ulcer disease has at the same time declined in step with a decrease in H. pylori infection. Many of the changes taking place mirror the Western experience of several decades ago. Astute observation of the epidemiology of emerging diseases combined with good scientific work will allow a clearer understanding of the key processes underlying these changes. With rapid modernization, lifestyle changes have been blamed for an increase in several diseases including gastroesophageal reflux disease, nonalcoholic fatty liver disease and colorectal cancer. A worrying trend has been the increase in obesity among Asians, which has been associated with an increase in metabolic diseases and various gastrointestinal cancers. Conversely, an improvement in living conditions has been closely linked to the decrease in GCA and H. pylori prevalence.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

More than half the world's population or approximately 4 billion people live in Asia. Changes in trends of disease in Asia would therefore impact significantly on the global heath burden. Major changes in disease and health is inevitable in the Asia–Pacific region as a result of dramatic socio-economic changes in the region and concomitant lifestyle changes.

For all diseases, an increased prevalence could be due to better diagnosis as well as a true increase in the frequency of disease. Observations of a decrease in disease prevalence are interesting and important as well. The changing epidemiology of a disease often provides valuable insights as to possible pathogenic mechanisms and the changing epidemiology in Asia allows us an opportunity to make such observations.

The purpose of this review is to study and summarize the changes that have taken place in the epidemiology of major gastrointestinal diseases: gastric cancer (GCA) and colorectal cancer (CRC), as well as that of acid-peptic diseases, including peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD) based on published data in the Asia–Pacific region.

GASTRIC CANCER

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

Gastric cancer remains one of the most common cancers in the Asia–Pacific region. In 2002, two Asia–Pacific countries, Korea and Japan, recorded the highest gastric cancer incidence in the world for both men and women.1 In absolute numbers, for the same year, close to 1 million new cases of GCA were diagnosed, more than half the cases were from East Asia, 41% from China and 11% from Japan. However Asia is a diverse continent and incidence rates vary greatly from country to country as well as between ethnic groups. Age standardized incidence rates in India, Thailand and the Philippines are among the lowest in the world and range from 10 to 15 per 100 000 per year.2 In multiracial Singapore, Chinese have the highest incidence rates compared to low incidence rates among Malays and Indians.2 Similarly in a case-control study from Malaysia, Chinese race was identified as a significant independent predictive factor for GCA.3

Food has been often implicated as cause of the high GCA incidence rates among Chinese, Koreans and Japanese. High salt content of oriental foods and the intake of preserved foods such as soya-bean paste soup and Kim-chi among Japanese and Koreans have been implicated as a cause.4–6 On the other hand, Indians appear to be protected because of the high intake of curries and chillies, which may contain gastro-protective factors such as curcurmin.7,8 Ultimately, causation of disease would depend on the interaction between host genetic factors and environmental factors including diet and H. pylori infection.

Broadly, ecologic comparison studies in Asian populations have shown a close association between H. pylori infection and GCA.9 Some anomalies exist. There is a high prevalence of H. pylori among both Chinese and Indians in a multiracial Asian population in Malaysia but an inordinately low GCA incidence among the latter has been observed and has been called the ‘Indian’ enigma.3 This fact is reiterated by the well reported high prevalence of H. pylori in the Indian population and the relatively low cancer incidence noted in Indian cancer registries.10,2

While the burden of GCA remains high in the Asia–Pacific region, age-standardized incidence rates (ASR) have started to show a decline. ASR from cancer registries in Osaka, Japan, Qidong county, China and Singapore for example, show a steady decline over the past 20 years (Fig. 1).11 Cancer statistics collected from the urban districts of Shanghai by the Shanghai Cancer Institute, showed a marked decline in ASR in men from 62 to 35.8 and in women from 23.9 to 17.5 per 100 000 population from 1979 to 1999.12,13 This is in keeping with observed trends noted in Western countries where GCA has been observed to have declined since the 1940s (Fig. 1).14

image

Figure 1. Time trends age-standardized incidence rates of gastric cancer in men from Western and Asian cancer registries showing declining incidence rates. Note the low incidence rates among Indians.11

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This decline is thought to be due to the decreased intake of salt and food preservatives following the widespread use of refrigeration of food in the West. Refrigeration has allowed greater intake of fresh fruits and vegetables with a higher level of antioxidants.15,16 This has been well shown in a study by Fei and Xiao from Shanghai where consumption of fresh fruits and vegetables and availability of home refrigeration was associated with a lower incidence of gastric cancer.17

H. pylori has now been identified as a critical factor in gastric carcinogenesis.18 With increasing awareness, diagnosis and treatment of the infection, prevalence rates of H. pylori have now also decreased throughout the world.19–21 However the decline in GCA preceded the discovery of H. pylori. Paradoxically, the prevalence of H. pylori, may in fact have also started to decline before its discovery. H. pylori is a marker of socioeconomic status and improvement in status with better personal and community hygiene has probably been a more important factor in the decrease in the prevalence of infection.22

Another important change with regard to GCA has been the change in the topography of GCA in Western patients which was first noted in the early 1990s. Cardia cancer has been reported to be the fastest growing gastrointestinal cancer in the West.23 However, such a change has not been noted in Asian countries where distally located tumors still predominate (Fig. 2).24,25

image

Figure 2. Comparison of subsite distribution of gastric cancer (men and women) from Western and Asian cancer registries.25

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Although incidence rates of GCA have declined, greater life expectancy and an increase in the elderly population, as is seen in Japan, would mean that the health burden in terms of actual numbers of GCA patients would remain the same or even increase.26

COLORECTAL CANCER

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

Colorectal cancer has long been considered a Western disease. There has however, been clear evidence that CRC incidence rates have been increasing in Asians.11 In the recent Globocan figures of 2002, ASR rates of CRC have increased markedly in Japan and among Singapore Chinese and are reported to be among the highest in the world.2 In several Asian countries, the ASR of colon and rectal cancer has now surpassed that of GCA.2

This changing epidemiology follows that of the West where CRC had been steadily over the past 40 to 50 years (Fig. 3). The increased incidence of CRC could be due to better detection and diagnosis of the cancer. With widespread availability of better health care services in Asia, flexible colonoscopy has become more readily available. However, the continuing rise in CRC rates points to a true increase in CRC.27 The reasons are likely to be similar to those in the West. Rising affluence with an increase in obesity and a decrease in physical activity have been implicated in CRC.28–30 On the other hand, the adoption of a westernized diet of higher protein and fat content has also been implicated as a cause for the increase in incidence.31,32 Without question, CRC will be the major GI cancer in the region in the coming years.

image

Figure 3. Time trends of age-standardized incidence rates of colorectal cancer in men from Western and Asian cancer registries showing increasing rates. Note the low incidence rates among Indians.11

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Another interesting observation is the anatomical left to right shift in location of CRC. This has been observed for many years in the West. Although recent reports from Asia have shown an overwhelming left side predominance (Table 1),33 some studies have shown a proximal shift. For example a study from Hong Kong, China has shown an increase in the proportion of proximal polyps and studies from Korea and Japan have shown an increase in the proportion of proximal tumors especially among women and in the elderly population (Fig. 4).34–36

Table 1.  Distribution of CRC in an Asian population.33 (Reproduced with permission.)
No1st lesion2nd lesion3rd lesion% of total
Rectum 90 0036.3
Sigmoid 6911032.3
Descending 25 3011.3
Transverse 13 11 6.0
Ascending 16 20 7.3
Caecum 15 20 6.9
Total228191
image

Figure 4. Time trends of the proportion (%) of patients = 70 years of age with proximal tumors.36 (Reproduced with permission.)

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ACID-PEPTIC DISEASES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

The marked change in the epidemiology of cancers is also seen with the acid-peptic diseases: peptic ulcer disease and gastroesophageal reflux disease.

Peptic ulcer disease

The decrease in prevalence of peptic ulcer disease has been documented in several studies from the region (Fig. 5).37–39 While the overwhelming majority of patients were diagnosed to have associated H. pylori infection, one study from Philippines has noted a steady decline in prevalence of H. pylori-associated ulcers.40 Reports on the prevalence of NSAID use and the increase in NSAID-associated ulcers have also been noted.41

image

Figure 5. Time trends – proportion of patients with duodenal ulcer, esophagitis and H. pylori infection in an endoscopy-based study.39 (Reproduced with permission.)

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Gastroesophageal reflux disease

Gastroesophageal reflux disease has been considered a rare disease in the East previously. Indeed earlier studies have shown an inordinately low prevalence of reflux esophagitis.42 Community-based studies have also shown a low prevalence of reflux symptoms. The situation has changed dramatically. More and better studies are now available, which have shown prevalence of reflux esophagitis approaching 20% and prevalence of reflux symptoms of 10–15%. More severe grades of esophagitis have also been noted although Barrett's esophagus remains uncommon.43

Helicobacter pylori infection

H. pylori underlies several gastrointestinal disorders including GCA and peptic ulcer disease. Reports from Asia have shown a steady decline of H. pylori over the years.44–47 Studies from Japan have linked the decrease in H. pylori incidence with an increase in GERD.48

OTHER GASTROINTESTINAL DISEASES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

Inflammatory bowel disease (IBD): ulcerative colitis and Crohn's disease have also been thought to be very uncommon diseases in Asians. Studies from Japan and China have, however shown marked increases in prevalence rates as well as absolute numbers of patients with IBD.49–52 Data from one study from northern India show inordinately high rates of ulcerative colitis comparable to that seen in the West.53 There is now enough evidence to show that IBD may be the next emerging GI disease in the Asia–Pacific region.54

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES

The epidemiological changes that have taken place over a relatively short interval of time point to the influence of exogenous factors. Broadly, changes to that result in a more ‘westernized’ lifestyle, have been blamed. Such changes that are relevant to our discussion include dietary changes, improved living conditions and a decrease in physical activity.

A change in diet to one that is rich in fat and protein has been implicated in the rise in incidence of CRC as well as GERD. This process could be brought about directly by the change in diet or through associated problems such as obesity. Dietary change compounded by a decrease in the level of physical activity has made obesity the fastest growing problem in the Asia–Pacific region.55 An epidemic of obesity-associated diseases such as ‘fatty liver’ has already been predicted.56

Paradoxically, dietary change has also meant a change to a better diet – one that contains less salt and preservatives. This has been thought to be the single most important factor in the decline in GCA rates. An improvement in living conditions and better personal and community hygiene has also resulted in the rapid decrease in the prevalence in H. pylori and as a consequence, a decline in the prevalence of associated gastroduodenal disease: peptic ulcer and GCA. A decrease in H. pylori infection has resulted in a healthier stomach with an increase in acid producing capacity which will contribute to the increase in GERD.57 An improvement in hygiene has conversely been implicated in the increase in IBD in Western populations.58 This may also be the case in the Asian population where an increase in prevalence has already been observed.

An important demographic factor to consider is the increase in the proportion of population that is elderly in the Asia–Pacific region. Apart from degenerative diseases, cancers including gastrointestinal cancers would increase and patterns of cancer will also change. Higher consumption of non-steroidal anti-inflammatory drugs in the elderly will result in an increase in gastrointestinal ulceration and associated complications particularly gastrointestinal bleeding despite the decrease in H. pylori associated ulcers.

Epidemiological change in disease is inevitable with time. The challenge for everyone is to identify putative factors and implement modifiable or remedial action to prevent the full deleterious effects of such changes.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GASTRIC CANCER
  5. COLORECTAL CANCER
  6. ACID-PEPTIC DISEASES
  7. OTHER GASTROINTESTINAL DISEASES
  8. DISCUSSION
  9. REFERENCES
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