Prevalence of irritable bowel syndrome in a multi-ethnic Asian population.

Abstract

Sirs, In relation to the recent article by Lu et al. on the prevalence, social impact and health-seeking behaviour of irritable bowel syndrome patients in Taiwan,1 we would like to share our own prevalence data on irritable bowel syndrome in a multi-racial Asian population. It is widely believed that irritable bowel syndrome is rather uncommon in Asia. Prevalence studies on irritable bowel syndrome in Asia have reported varying results: Singapore (2.3%),2 Thailand (4.4%),3 Hong Kong (6.6%, Rome II criteria),4 China (22.8%, Manning criteria),5 Bangladesh (24.4%, Manning criteria; 8.5%, Rome I criteria)6 and Taiwan (22.1%, Rome II criteria).1 This may be due to the use of questionnaires based on different definitions of functional gastrointestinal disorders and to variations in the study populations and sampling methods. Differences in socio-economic status and cultural practices and the rapidly changing lifestyle of the affluent East Asian population may also be responsible for the disparity in the reported prevalence rates of irritable bowel syndrome. Racial differences within different communities in the same country (if any) have remained largely unexplored. Malaysia affords a suitable population base to study such differences in the prevalence of irritable bowel syndrome. We therefore undertook to estimate the prevalence of irritable bowel syndrome using a locally validated Rome II Modular Questionnaire.7 Additional questions pertaining to heartburn, acid regurgitation, physician visits and treatment (Western or alternative medicine) were also included. The study population was from the State of Perak (population approximately 2 million) whose ethnic composition is as follows: Malays, 51.4%; Chinese, 31.3%; Indians, 12.8%; others, 4.5%.8 This ethnic distribution and basic demographic characteristics are representative of the rest of west Malaysia. Subjects were identified from the National Household Sampling Frame created for the 2000 Population and Housing Census.8 Subjects were recruited from both rural and urban areas using a race-stratified disproportionate random sampling procedure to ensure a sufficient number of members of ethnic minorities. To avoid ethnic ambiguity, only those subjects without racial admixture in the immediate two preceding generations were recruited. A team of interviewers trained by one physician (SR) interviewed the subjects at home in the languages/dialect usually understood and spoken by the respondents. A total of 1179 selected individuals were interviewed, but questionnaires returned by 949 subjects only (314 Malays, 314 Chinese, 321 Indians) were successfully analysed. They were aged between 18 and 81 years (mean, 33.6 years; s.d., 13 years); 478 were males and 471 were females. Irritable bowel syndrome was diagnosed in 148 individuals (39 Malays, 55 Chinese, 54 Indians; P = 0.16), with a female to male ratio of 1.4. (irritable bowel syndrome subjects vs. controls: odds ratio, 0.65; 95% confidence interval, 0.45–0.94; P = 0.01). Ethnic-adjusted irritable bowel syndrome prevalence rates were as follows: Malays, 12.4%; Chinese, 17.5%; Indians, 16.8%. The race-standardized prevalence of irritable bowel syndrome was 14% with no significant ethnic differences (P = 0.08). Eighty-three patients with irritable bowel syndrome (56%) reported heartburn at least once a year, compared with 236 in the control group (29%) (irritable bowel syndrome subjects vs. controls: odds ratio, 3.06; 95% confidence interval, 2.10–4.4; P < 0.001). There were no significant differences in higher educational attainment or socio-economic class between subjects with irritable bowel syndrome and controls. Constipation-predominant irritable bowel syndrome was recorded in 36.5%, diarrhoea-predominant in 35.1% and mixed pattern in 28.4%. Amongst those with irritable bowel syndrome, 64 (43.2%) had consulted a doctor and 74 (50%) had taken medication (Western and alternative). Our data confirmed the reported association between gastro-oesophageal reflux and irritable bowel syndrome.9 In a large community study in the UK, Kennedy et al. reported that 43% of irritable bowel syndrome consulters had gastro-oesophageal reflux symptoms.9 In contrast, only 25% of those without irritable bowel syndrome had reflux symptoms of heartburn and/or acid regurgitation. It has been postulated that gastro-oesophageal reflux and irritable bowel syndrome share a common denominator,10 although the mechanisms involved are as yet undetermined. The prevalence of irritable bowel syndrome in our multi-racial population approached published Western figures with no significant ethnic differences. There was a preponderance of females with irritable bowel syndrome, as is the case in Bangladeshi and Caucasian irritable bowel syndrome individuals.6, 11-13 In contrast, irritable bowel syndrome studies in Singapore, Hong Kong and Taiwan did not reveal a gender difference.1, 2, 4 The reason for this discrepancy is unclear.