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Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Background : Colonic diverticular disease is more common in Western populations than in developing countries.

Aim : To determine whether the frequency of colonic diverticular disease is different in British patients of Indian-subcontinent Asian origin compared with other ethnic groups.

Methods : All colonoscopies performed over a 3-year period in a London hospital were studied. Patients of Indian-subcontinent Asian origin were identified by name.

Results : Five of 134 Indian-subcontinent Asian males (4%) had colonic diverticular disease, compared with 278 of 1268 patients of other ethnic groups (22%; P < 0.001). Five of 91 Indian-subcontinent Asian females (6%) had colonic diverticular disease, compared with 333 of 1486 patients of other ethnic groups (23%; P < 0.001). Although patients of Indian-subcontinent Asian origin (54.8 ± 15.8 years) were younger than those of other ethnic groups (60.3 ± 17.8 years; P < 0.0001), the ethnic difference in the frequency of diverticular disease persisted even when age was taken into account.

Conclusion : There is a lower frequency of colonic diverticular disease in Indian-subcontinent Asians presenting for colonoscopy, compared with other ethnic groups. This cannot be explained by sex or age differences. Our findings require confirmation, but may provide opportunities for research into the aetiology of colonic diverticular disease.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Colonic diverticular disease is a common condition and the cause of significant morbidity and mortality in the Western world.1–3 Being especially a disease of the elderly, it is becoming a clinical problem of increasing proportions.4 There are marked temporal and geographical variations in the frequency of colonic diverticular disease. It was rare prior to the latter part of the 20th century, but then rapidly became a commonly recognized clinical entity.1, 5–8 It is less common in developing countries, such as Singapore and Fiji, compared with the West.8, 9 Colonic diverticular disease preferentially affects the sigmoid and left colon in Western patients. In contrast, when colonic diverticular disease occurs in oriental populations, right-sided disease predominates.10–12

Geographical and ethnic differences in disease frequency may be due to genetic or environmental influences, or a combination of both. Indians form one of the main ethnic groups in Fiji and Singapore. As there are genetic and dietary differences between English residents from the Indian subcontinent and their white counterparts, we hypothesized that the frequency and pattern of colonic diverticular disease in England may be different for Indian-subcontinent Asians compared with other individuals. We therefore analysed the colonoscopy database in our institution, with special reference to the effect of ethnicity on the frequency and pattern of colonic diverticular disease.

Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

All endoscopies performed at St George's Hospital, London, are recorded in a computer database. Colonoscopy records for the 3-year period from October 1999 to October 2002 were retrieved. Patients of Indian-subcontinent Asian origin were identified by surname and forename. This method has previously been shown by ourselves and others to have acceptable sensitivity and specificity in the identification of Asian ethnic origin.13, 14 In order to ensure that the classification of race was correct, we checked the hospital database of all patients who appeared to be of Indian-subcontinent Asian origin by name. If information regarding ethnic origin was available, the patient was re-classified whenever appropriate. Care was taken to ensure that patients who had repeat colonoscopies were only counted once.

Patients with diverticular disease were identified and numbers calculated. Patient demography, sites of involvement of diverticular disease and indication for colonoscopy in each case were recorded. The chi-squared test was used to compare categorical data and Student's t-test to compare numerical data. Probability values of < 0.05 were considered to be significant.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Over the study period, 2979 patients had colonoscopies performed. Of the 244 patients whose names appeared to be of Indian-subcontinent origin, 185 (76%) had their ethnicity recorded on the hospital database. Of these, 19 (10%) had other ethnic origins (white, 12; Afro-Caribbean, 6; Chinese, 1). Having taken these into account, 225 patients in our series were Indian-subcontinent Asians, while 2754 belonged to other ethnic groups (Table 1). Indian-subcontinent Asians had an average age of 54.8 years and a male to female ratio of 1.47 : 1. Patients of other ethnic groups had an average age of 60.3 years and a male to female ratio of 0.85 : 1 (P < 0.001). In this cohort of patients, Indian-subcontinent Asians were significantly younger than patients of other ethnic groups, regardless of whether the two sexes were considered separately or together (Table 1).

Table 1.  Demography of patients undergoing colonoscopy
 Indian-subcontinent AsiansOther ethnic groupsP
NumberMean age ± s.d. (years)NumberMean age ± s.d. (years)
  1. s.d., standard deviation.

Males13456.3 ± 16.49126860.4 ± 17.0< 0.001
Females 9152.4 ± 14.6148660.1 ± 18.4< 0.0001
All22554.8 ± 15.8275460.3 ± 17.8< 0.0001
Male : female ratio1.47 : 1 0.85 : 1 < 0.001

In patients of Indian-subcontinent Asian origin, the country of birth was recorded for eight of the ten patients with diverticular disease and, of these, one was born in Britain (13%). Of the 215 patients of Indian-subcontinent Asian origin without diverticular disease, the country of birth was recorded in 143 cases (67%). Of these, 20 patients (14%) were born in Britain (N.S.).

Colonic diverticular disease was generally an incidental finding. One to three indications were entered for each patient undergoing colonoscopy, and these indications were similar in the two groups (Table 2). The most common indication was rectal bleeding, and was the reason for investigation in 28% of Indian-subcontinent Asians and 22% of other ethnic groups. Other frequent indications were anaemia and change of bowel habit. Proportionately more patients of Indian-subcontinent Asian origin were colonoscoped for anaemia (31%) compared with patients of other ethnic groups (16%; P < 0.001). In contrast, fewer patients of Indian-subcontinent Asian origin were colonoscoped for a family history of colorectal cancer (4%) compared with patients of other ethnic groups (12%; P < 0.001).

Table 2.  Indications for colonoscopy
 Indian-subcontinent AsiansOther ethnic groups
  • A number of patients had more than one indication for colonoscopy.

  • *

     P < 0.05.

  •  P < 0.001.

Number (%)225 (100)2754 (100)
Indications
 Rectal bleeding 63 (28) 609 (22)*
 Anaemia 70 (31) 445 (16)
 Change in bowel habit 57 (25) 579 (21)
 Colitis assessment/  surveillance 28 (12) 274 (10)
 Cancer follow-up 14 (6) 179 (6)
 Family history   colorectal cancer 10 (4) 328 (12)
 Polyp follow-up 15 (7) 281 (10)
 Abdominal pain 15 (7) 223 (8)

Ten of the 225 Indian-subcontinent Asians (4.4%) had diverticular disease, compared with 611 of 2754 subjects in the other ethnic groups (22.2%; P < 0.001) (Table 3). There were no gender differences for patients of either ethnic group (Table 3). Patients with diverticular disease were older than those without (Table 4). This was the case for both patient groups and for both sexes, except that, for male Indian-subcontinent Asians, the difference did not reach statistical significance. As diverticular disease was more prevalent amongst older individuals, and as Indian-subcontinent Asians were younger than subjects of other ethnic groups, the age-specific prevalence of diverticular disease were calculated for the two patient groups (Table 5). For patients aged between 45 and 64 years, three of 88 Indian-subcontinent Asians (3.4%) had colonic diverticular disease, compared with 152 of 898 subjects (16.9%) of other ethnic groups (P < 0.01). For patients aged between 65 and 84 years, the corresponding numbers were seven of 72 (9.7%) and 375 of 1079 (34.8%), respectively (P < 0.001). These differences were also statistically significant for either sex (data not shown). Therefore, the lower frequency of colonic diverticular disease in Indian-subcontinent Asians was not merely an artefact relating to their younger age structure.

Table 3.  Proportions of patients with diverticular disease (DD)
 Indian-subcontinent AsiansOther ethnic groupsP
All patientsPatients with DD (%)All patientsPatients with DD (%)
Males1345 (3.7)1268278 (21.9)< 0.001
Females 915 (5.5)1486333 (22.4)< 0.001
All22510 (4.4)2754611 (22.2)< 0.001
Table 4.  Diverticular disease, ethnicity and age
 Diverticular diseaseNo diverticular diseaseP
  • Indian subcontinent Asians vs other ethnic groups.

  • *

     N.S.

  • †‡ P < 0.05.

Indian-subcontinent Asians
 Males65.7 ± 4.2*55.9 ± 16.6N.S.
 Females62.6 ± 5.4†51.8 ± 14.8N.S.
 All64.9 ± 5.1‡54.3 ± 16.00.032
Other ethnic groups
 Males71.1 ± 11.3*57.4 ± 18.4< 0.0001
 Females73.0 ± 11.2†56.4 ± 18.4< 0.0001
 All72.1 ± 11.3‡56.9 ± 17.8< 0.0001
Table 5.  Age-specific prevalence of diverticular disease (DD) by ethnicity
Age (years)Indian-subcontinent AsiansOther ethnic groupsP
DDTotalDDTotal
< 45 0 63  4 601N.S.
45–64 3 88152 898< 0.01
65–84 7 723751079< 0.001
> 84 0  2 80 176N.S.
All102256112754< 0.001

All 10 patients of Indian-subcontinent Asian origin with diverticular disease had disease confined to the left colon. Of the 611 patients in the other ethnic groups with diverticular disease, 499 (82%) had left-sided disease. Forty-two patients (7%) had disease extending from the left colon to the transverse colon. In a further 58 patients (9%), there was disease affecting the left colon, transverse colon and the ascending colon. Four patients (1%) had purely right-sided disease. The extent of disease was not specified in eight patients (1%). There were no gender differences in the distribution of diverticular disease.

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Colonic diverticular disease is uncommon in the East. In oriental countries, westerners are more likely to be affected than the indigenous populations. In a study involving four teaching hospitals in Scotland, Singapore, Nigeria and Fiji, annual admission rates for colonic diverticulitis were 12.88 per 100 000 population in Scotland, compared with 0.17 in Nigeria.6 In Singapore, the annual admission rate was 0.13 per 100 000 population for indigenous subjects, compared with 5.41 for Europeans. Similarly, in Fiji, the annual admission rates were 0.34 per 100 000 for Indian Fijians, 0.21 per 100 000 for non-Indian Fijians, and 7.62 per 100 000 for Europeans. Our finding of a lower prevalence of colonic diverticular disease in Indian-subcontinent Asians, when compared with other ethnic groups resident in England, is therefore consistent with the results from these earlier studies.

Although the sex ratio differed between patients of Indian-subcontinent Asian origin and subjects of other ethnic groups, this could not explain the different frequencies of diverticular disease, as the prevalence of diverticular disease was unaffected by gender. Although patients of Indian-subcontinent Asian origin were younger than subjects of other ethnic groups, these ethnic differences remained even when age was taken into account.

Colonoscopy is less sensitive for the diagnosis of colonic diverticular disease when compared with barium studies or autopsy. However, any limitation of colonoscopy in the diagnosis of colonic diverticular disease will apply equally to patients of different ethnic groups, and so our finding of ethnic differences should remain valid.

Ethnic differences in the frequency of disease may be due to genetic or environmental factors, or a combination of both. Environmental differences may change over a period of years, whereas genetic ones do not. The traditional view is that colonic diverticular disease is caused by deficient intake of fibre in the Western diet. A low-fibre diet tends to be associated with a prolonged colonic transit time and a decreased volume and water content of stool. This may increase colonic segmentation and intraluminal pressure, which in turn predisposes to diverticula formation.1, 15 It is possible that the lower frequency of colonic diverticular disease in Indian-subcontinent Asians is due to a higher intake of dietary fibre. Further studies are required to confirm or refute this hypothesis.

A review of barium enemas in Singapore showed that, in 70% of patients with colonic diverticular disease, only the right colon was affected.10 In Australian patients, by contrast, only 5% of cases were right-sided.16 Colonic diverticular disease was confined to the left colon in 71% of Australian patients, compared with only 22% of cases in the Singapore series. Patients with right-sided diverticular disease were younger than those with left-sided disease by approximately 10 years.10 In 42% of cases of right-sided diverticular disease, the diverticula were solitary. A large radiological study from Japan showed an increase in right-sided diverticular disease over a 15-year period, from 1982 to 1997, whereas the frequency of left-sided disease remained unchanged.11 The prevalence of left-sided diverticular disease increased with age, but right-sided disease was most prevalent in middle-aged patients. As the number of diverticula per patient did not change over age or time, right-sided diverticula are probably acquired, but self-limited in development.11 The occurrence of right-sided diverticular disease was not associated with fruit or vegetable use or laxative intake, but was positively associated with meat consumption.17 In the present series, the left colon was predominantly affected, even in those of Indian-subcontinent extraction, but the patient numbers in the Indian-subcontinent Asian group were too small to allow any firm conclusion to be made.

Further studies are warranted to confirm our finding that colonic diverticular disease is less common in Indian-subcontinent Asians when compared with patients of other ethnic groups. Our data did not show any difference in the frequency of colonic diverticular disease between first- and second-generation Indian-subcontinent Asians, but the patient numbers were small. Furthermore, at the present time, second-generation Indian-subcontinent Asians tend not to have reached the age normally associated with colonic diverticular disease. It would be interesting to re-address this issue in years to come, as such a difference may indicate environmental influences, e.g. diet. Future studies should also examine the prevalence of right- and left-sided disease in patients of Indian-subcontinent Asian origin, and determine whether different subsets of Indian-subcontinent Asians have different frequencies and/or subsites of colonic diverticular disease.

Acknowledgements

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

This study was presented to the British Society of Gastroenterology in March 2003. The authors would like to thank Dr Sonia Saxena for her helpful comments.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References
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