Alternating bowel pattern: what do people mean?

Transcription

1 Alimentary Pharmacology & Therapeutics Alternating bowel pattern: what do people mean? R. S. CHOUNG*, G. R. LOCKE III*, A. R. ZINSMEISTER, L.J.MELTONIIIà &N.J.TALLEY* *Dyspepsia Center and Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, MN; Department of Health Sciences Research Division of Biostatistics, Mayo Clinic College of Medicine, Rochester, MN; àdivision of Clinical Epidemiology, Mayo Clinic College of Medicine, Rochester, MN, USA Correspondence to: Dr G. R. Locke III, Professor of Medicine, Mayo Clinic, 200 First Street SW, W-19A, Rochester, MN 55905, USA. Publication data Submitted 27 January 2006 First decision 14 February 2006 Resubmitted 20 March 2006 Accepted 3 April 2006 SUMMARY Background With the introduction of new therapies, the subgrouping of patients based on bowel pattern has become important. However, the appropriate definition of an alternating bowel pattern remains unclear. Aim To determine if specific symptoms are reported by people with an alternating bowel pattern. Methods Using the Rochester Epidemiology Project, a series of population-based surveys were undertaken in which valid self-report gastrointestinal symptom questionnaires were mailed to 4029 randomly selected members of the community. One question asked was How would you describe your usual bowel pattern in the last year? Results 3022 subjects (74%) provided questionnaire data and 2718 were eligible for this analysis, the mean age was 57 years, with a range of years (median ¼ 61). Of these, 9.2%, 2.5% and 7.6% reported their usual bowel pattern as being constipated, diarrhoea, or alternating respectively. At least 50% of those reporting alternating bowel pattern reported incomplete evacuation (63%), urgency (57%), straining (55%) and loose stool (50%). The proportion of alternators reporting each individual symptom was between that of diarrhoea and constipation except for mucus and incomplete evacuation; however, no symptom was unique to alternators. Conclusion People who self-report an alternating bowel pattern appear to represent a blend of constipation and diarrhoea symptoms, rather than a distinct subgroup. Aliment Pharmacol Ther 23, ª 2006 The Authors 1749 doi: /j x

2 1750 R. S. CHOUNG et al. INTRODUCTION Recently two new therapies, alosetron and tegaserod, have been developed for irritable bowel syndrome (IBS). It is important to note that they have very different effects. 1 4 Alosetron helps diarrhoea-predominant IBS (IBS-D) 1, 2 whereas tegaserod helps constipation-predominant IBS (IBS-C). 3, 4 The development of these therapies has therefore led to a need to subclassify IBS. Thus, the Rome committees suggested definitions for IBS-D and IBS-C. 5, 6 This subgrouping leaves a group of people with IBS who are neither constipation-predominant nor diarrhoea-predominant; they may have both or they may have neither. The terms alternating IBS and mixed IBS have recently been used to define these groups. 7, 8 At present, the appropriate definition of an alternator is not clear. Drossman et al. 9 suggested that mixed IBS is not fulfilling criteria for either IBS-C or IBS-D, whereas alternating IBS is a change in bowel habit over time. Rather than impose definitions, however, we sought to understand what comprised an alternating bowel pattern by allowing people in the community to selfreport their typical bowel pattern. Our aim was to determine if a specific set of symptoms was associated with people reporting an alternating bowel pattern. MATERIALS AND METHODS Subjects The Olmsted County, MN population comprises approximately subjects, of which 90% are white; sociodemographically, the community is similar to the United States white population. 10 Over 95% of County residents receive their medical care from one of the two group practices in the community (Mayo Medical Center and Olmsted Medical Center). Mayo Clinic has maintained a common medical record system with its two affiliated hospitals (Saint Marys and Rochester Methodist) for over 90 years. Recorded diagnoses and surgical procedures are indexed, including the diagnoses made for out-patients seen in office or clinic consultations, emergency room visits or nursing home care, as well as the diagnoses recorded for hospital in-patients, at autopsy examination or on death certificates. This system was further developed by the Rochester Epidemiology Project, which created similar indices for the records of other providers of medical care to local residents, most notably the Olmsted Medical Group and its affiliated Olmsted Community Hospital (Olmsted Medical Center). Thus, details of the medical care provided to the residents of the County are available for study. Annually, over 80% of the entire population is attended by one or both of these two practices, and nearly everyone is seen at least once during any given 3-year period. 10 Therefore, the Rochester Project medical records linkage system also provides what is essentially an enumeration of the population from which samples can be drawn. As approved by the Institutional Review Boards of the Mayo Clinic and Olmsted Medical Center, we used this system previously to draw a series of random samples of Olmsted County residents stratified by age (5-year intervals between 20 and 94 years) and sex (equal numbers of men and women). Survey methods As part of previous investigations, these randomly selected Olmsted County residents were mailed valid self-report gastrointestinal (GI) symptom questionnaires. The Bowel Disease Questionnaire (BDQ) was mailed to subjects years of age, and the Elderly Bowel Syndrome Questionnaire (EBSQ) was mailed to subjects years of age. The questionnaires have been shown to be understandable, easily completed and to have adequate validity. 13, 14 The BDQ consists of 46 GI symptoms, while the EBSQ has 33 symptom items; 26 of these items are identical on both questionnaires, and these were considered in the analysis. The BDQ also included the Somatic Symptom Checklist (SSC), whereas the EBDQ did not. This checklist consists of 12 non-gi and five GI symptoms or illnesses, and subjects are instructed to indicate how often each symptom occurred (0 ¼ not a problem to 4 ¼ occurs daily) and how bothersome each was (0 ¼ not a problem to 4 ¼ extremely bothersome when occurs) during the past year, using separate 5-point scales. The study questionnaire and an explanatory letter were mailed to this age- and gender-stratified sample of 4029 residents of Olmsted County. Reminder letters were mailed at weeks 2, 4 and 7 to non-responders. Subjects who indicated at any point that they did not wish to complete the survey were not contacted further. Otherwise, non-responders were contacted by telephone at week 10 to request their participation and verify their residence within the County. A completed questionnaire was returned by 3022 subjects, giving a response rate of 74%. Among the 3022 subjects who

3 ALTERNATING BOWEL HABITS 1751 completed a questionnaire, 304 (10.1%) had subsequently denied authorization to use their medical records for research, 15 leaving 2718 subjects for this analysis. The questionnaires included one question that asked, How would you describe your usual bowel pattern in the last year? The response options were normal, constipated [self-reported constipation (SRC)], diarrhoea (SRD), and alternating constipation and diarrhoea (SRA). This question was used to define the study groups used in the analysis. The reliability of this specific question regarding self-reported bowel habit was 0.72 (95% CI: ) with 89% agreement 14 and the median j-statistic for all questions was Three GI symptom complexes were defined by specific symptom criteria, as follows: Constipation Defined as two or more of the following complaints in the prior 12 months: straining >25% of the time, hard stools >25% of the time, feeling of incomplete evacuation >25% of the time, or <3 stools/week >25% of the time. Diarrhoea Defined as two or more of the following complaints in the prior 12 months: loose or watery stools >25% of the time, urgency >25% of the time, or more than 3 stools/day >25% of the time. Irritable bowel syndrome Defined as abdominal pain more than six times in the prior year, in combination with two or more of the following symptoms (referred to as the Manning symptom criteria): 18 (i) pain that was often relieved by defecation (more than 25% of the time); (ii) looser stools often when pain began; (iii) more frequent stools often when pain began; (iv) abdominal distension often; (v) a feeling of incomplete evacuation often and (vi) mucus per rectum. Statistical methods To identify symptoms that are described differently among groups defined by their self-reporting of bowel pattern (normal, constipation, diarrhoea, alternating), logistic regression models were examined in which each individual symptom was considered as the dependent variable and bowel pattern groups (as dummy regression variables) were the predictors. In addition to the individual symptoms (i.e. straining, urgency, incomplete evacuation, hard stool, bowel movement frequency, loose bowel movement, pain frequency, mucus, pain severity and pain relief by bowel movement), three symptom complexes (i.e. constipation, diarrhoea, IBS) were also assessed as response (dependent) variables in separate logistic regression models. A generalized logit link function was used for symptoms with more than two categories (e.g. pain frequency). The regression models were set up with normal bowel pattern group as the reference level (i.e. SRC, SRD, SRA vs. normal) and specific pairwise contrasts of the regression coefficients were used to obtain the odds ratio (OR) for each symptom (or symptom complex) for SRA relative to SRC and SRA relative to SRD. Odds ratios and 95% confidence intervals (CI) were calculated based on the estimated regression coefficients and their standard errors from the logistic regression models. All P-values were two-sided, and P-values <0.05 were considered statistically significant. In addition, these models were analysed separately for those above and below 60 years of age. RESULTS Of the 2718 Olmsted County residents who were eligible for this analysis, the mean (s.d.) age was 57 (19) years, with a range of years (median ¼ 61); 63% were women. The proportions reporting each bowel pattern were as follows: 9.2% had SRC, 2.5% had SRD and 7.6% had SRA. The 206 subjects with SRA had a mean age of 54 years, and 63% were female. Subjects reporting SRA had smaller ORs for being older than 50 years relative to those reporting normal bowel pattern or SRC, and greater ORs for being female than those reporting a normal bowel pattern. A subset of subjects had been mailed questionnaires containing the SSC, and among the corresponding respondents, a total of 1462 subjects (54.4%) completed the items to compute an SSC score (55.3%, 34.4%, 73.9%, 62.6% in those reporting normal, constipation, diarrhoea and alternating bowel habit, respectively), SSC scores were significantly higher in SRA (vs. normal and SRC, P < 0.005) but not different from SRD. Among those in the SRA group, 39% reported bowel function consistent with a classification of constipation only, 16% with diarrhoea

4 1752 R. S. CHOUNG et al. % Constipation only Diarrhoea only only, 20% with both, and 25% neither bowel pattern. Figure 1 shows the proportion by gender of those with SRA who met criteria for constipation only, diarrhoea only, both and neither. No significant gender differences were noted. Overall 16% of subjects met IBS by Manning criteria. Among subjects meeting Manning IBS criteria, 19% reported a constipation bowel habit, 8% diarrhoea, 23% alternating and 50% normal bowel habit. Among subjects not meeting Manning IBS criteria, 7% 20 Both Male Female Neither Figure 1. Percentage of Olmsted County, MN residents with self-reported alternating bowel pattern (n ¼ 206) who met symptom criteria for constipation only, diarrhoea only, both, or neither. reported a constipation bowel habit, 1% diarrhoea, 4% alternating and in 86% a normal bowel habit. Among subjects with SRC, 33% met Manning criteria for IBS, among those SRD, 54% met Manning IBS criteria and among those reporting SRA, 50% met Manning criteria for IBS, while in those reporting a normal bowel habit, 10% met Manning IBS criteria. The ORs for meeting symptom criteria of constipation were increased for SRA vs. normal (OR ¼ 10.6, 95% CI: ) and vs. SRD (OR ¼ 15.2, 95% CI: ) but decreased vs. SRC (OR ¼ 0.3, 95% CI: ). Correspondingly, the ORs for meeting symptom criteria of diarrhoea were increased in SRA vs. normal (OR ¼ 11.6, 95% CI: ) and vs. SRC (OR ¼ 27.5, 95% CI: ) but decreased relative to SRD (OR ¼ 0.2, 95% CI: ). The ORs for IBS were increased in SRA relative to normal (OR ¼ 8.7, 95% CI: ) and relative to SRC (OR ¼ 2.0, 95% CI: ) but not SRD (OR ¼ 0.9, 95% CI: ). The distribution of individual abdominal symptoms among the bowel pattern subgroups is summarized in Table 1. As expected, symptoms of constipation and diarrhoea were frequently reported by people with SRC and SRD, respectively. Among the subjects with SRA, just over half reported incomplete evacuation (63%), urgency (57%), straining (55%) and loose stool (50%; Table 1). Also among SRA, 35% reported mucus that Symptom Percentage of the following subgroups with symptom Normal (n ¼ 2164) Constipation (n ¼ 250) Diarrhoea (n ¼ 69) (n ¼ 206) Table 1. Demographic characteristics and abdominal symptoms among self-reported bowel pattern subgroups Age over 50 years Female gender Pain severe or very severe Pain several times each week or more Loose bowel movement Frequent BM Feeling of incomplete evacuation Mucus Urgency Straining Hard stool Bloating Pain relief with BM More BMs with pain BM, bowel movement.

5 ALTERNATING BOWEL HABITS 1753 was the highest proportion among the three groups. The reporting of feelings of incomplete rectal evacuation was 63% in SRA when compared with 60% in SRC and 42% in SRD. The ability of the self-report bowel pattern groups to predict individual symptoms is shown in Table 2. Logistic regression analysis indicated that all of the symptoms assessed (except for frequent bowel movements) were significantly associated with SRA relative to normal (P < 0.05). Significantly increased ORs in SRA relative to SRC were observed for urgency, frequent stools, loose stools, mucus, frequent and severe abdominal pain, while decreased ORs were observed for straining and hard stools. In comparing SRA with SRD, increased ORs for straining, hard stools and incomplete evacuation were observed, but ORs were decreased for urgency, frequent bowel movements and loose stools. We analysed these results separately for patients younger and older than 60 years of ago. However, we found there were no interaction by age for the associations between individual symptoms and self-reported bowel patterns. Thus, for constipation symptoms, the ORs were higher for SRA than SRD but lesser for SRA than SRC. For diarrhoea symptoms, the ORs were higher for SRA than SRC but lower for SRA than SRD. However, mucus and feelings of incomplete rectal evacuation were reported by a higher proportion of those with SRA than either SRC or SRD. For mucus per rectum, the association with SRA was significant compared with SRC but not SRD; for the feeling of incomplete evacuation the association with SRA was significant compared with SRD but not SRC. DISCUSSION Recently, questions about who is an alternator in IBS have increased because of its apparent frequency in IBS and the increasing need to accurately subclassify IBS for therapeutic targets. 19, 20 However, no criteria were suggested for the alternator IBS subgroup by the Rome committee, and despite a relative lack of attention, the alternator IBS subgroup appears to represent approximately one-third of IBS patients. 21, 22 In our study, we found the proportion with SRA bowel pattern to be high (7.6%) based on a community sample, in comparison, the proportion with SRD was 2.5% and SRC was 9.2%. There is actually little epidemiological data on self-reported alternating bowel habit. Our data are similar to the study of Agreus et al. 23 They reported the overall prevalence of alternating bowel pattern in a Swedish population-based study was 6.2%. Among those with SRA, 20% met symptom definitions of both constipation and diarrhoea by specific criteria, 39% met the definition of constipation and 16% met the definition of diarrhoea; 25% did not meet either definition. Among the 2718 subjects for whom full data were available, 444 (16%) met Manning criteria. This proportion of IBS is similar to previous studies. Talley Table 2. Associations between individual symptoms and selfreported bowel patterns [OR (95% CI)] Symptom vs. normal vs. constipation vs. diarrhoea Straining 8.0 ( )* 0.2 ( )* 20.2 ( )* Urgency 8.8 ( )* 6.2 ( )* 0.5 ( )* Incomplete evacuation 11.6 ( )* 1.2 ( ) 2.5 ( )* Hard stool 4.4 ( )* 0.2 ( )* 27.3 ( )* Frequent BM 2.0 ( ) 31.2 ( )* 0.1 ( )* Loose BM 5.1 ( )* 7.5 ( )* 0.5 ( )* Mucus 6.3 ( )* 3.1 ( )* 1.5 ( ) Pain severity 10.6 ( )* 2.5 ( )* 0.7 ( ) (severe/very severe) Pain relief by a BM 4.7 ( )* 1.5 ( ) 1.4 ( ) More BM with pain 4.9 ( )* 4.6 ( )* 0.5 ( )* Frequent pain (>1/week) 11.7 ( )* 2.6 ( )* 0.8 ( ) BM, bowel movement. * P < Odd ratios (95% CI) in alternator relative to normal, constipation and diarrhoea.

6 1754 R. S. CHOUNG et al. et al. 24 reported that the prevalence of IBS in a geriatric population sample is similar to the prevalence of a middle-age population sample. Interestingly, about 50% of the SRA group met the definition of IBS by the Manning criteria. Recent studies have tried to define an alternator group in IBS, but no consensus exists. Drossman et al. 9 suggested that an alternator in IBS patients be defined as at least one change between IBS-D and IBS-C by Rome II criteria over a 1-year period. However, they did not study whether different characteristics existed in alternators compared with constipation- or diarrhoea-type in IBS. Tillisch et al. 7 defined the subgroups of IBS using diagnostic criteria based on stool consistency. They suggested that stool consistency provided the most simple and specific means of characterizing alternators in patients with IBS. However, this study was not population-based, as subjects were recruited from a tertiary referral centre or by advertisement. Mearin et al. 20 reported that among those with IBS by Rome I criteria, 66% considered themselves to have constipation. Yet among the 38 people who had what they called alternating IBS by Rome I, just 8% reported constipation. Among 40 people with alternating IBS by Rome II, the majority had constipation but no actual numbers are given. A changing of the definition between Rome I and Rome II leads to very different results. In this study, the sample size of people with IBS-A and the subjects with IBS who self-reported having an alternating bowel patterns was quite small. In the Mearin et al. study, 20 among those who self-reported alternating bowel habit, about 30% had constipation, 30% had diarrhoea and about 40% had alternating IBS subtype. However, our study revealed, among subjects meeting Manning IBS criteria, 19% reported a constipation bowel habit, 8% diarrhoea, 23% alternating and 50% normal bowel habit. This highlights the issue of whether alternators include people with both diarrhoea and constipation or neither? We found that bowel symptoms were quite common in people with SRA. For most symptoms; the proportion in SRA was higher than normal and was between SRC and SRD. Two symptoms seemed different: the subjects with SRA reported passage of mucus and feelings of incomplete evacuation more often than people with SRD or SRC. However, our study could not identify a distinct subgroup of symptoms that were reported by alternators. Those with SRA had symptoms of both constipation and diarrhoea. Thus, self-reported alternating bowel pattern seems to suggests a combination of bowel patterns rather than a distinct pathophysiology. The strengths of the present study include the investigation of a random community sample who was not seeking health care for their bowel complaints, which should have minimized selection bias. The fact that we employed a previously validated self-report symptom questionnaire also increases confidence in the results. 13 Those with SRC had more constipation symptoms than other groups, while those with SRD had more diarrhoea symptoms than other groups. This may just suggests that these two groups are better at judging their bowel habit, as reported by Mearin et al. 20 This study also had limitations. In particular, prospective diary data were not available to confirm the self-reported information. These data cannot be generalized to the whole population because the racial composition of this community is predominantly Caucasian. 10 The prevalence of bowel pattern may vary across different countries and cultures, but at minimum our data are probably generalizable to the US Caucasian population. Comparable studies in other populations are necessary. Because our study population had a median age of 61 years, these results are more applicable to older individuals. Still we did not identify any significant age effects. We conclude from this population-based study that self-reporting an alternating bowel pattern is associated with passage of mucus and, to a lesser extent, the feeling of incomplete evacuation, but that people who self-report alternating bowel patterns cannot be classified into a distinct subgroup. Alternating bowel pattern appears to reflect a combined state of both constipation and diarrhoea. Further work to understand what characterizes an alternator, and the relationship between alternating bowel pattern, constipation and diarrhoea, is warranted. ACKNOWLEDGEMENTS This study was sponsored in part by Novartis Pharmaceuticals Corporation and the Mayo Foundation. The authors would like to thank Cathy Schleck for her assistance with data analysis and Mary Jo Philo for her assistance in the preparation of the manuscript.

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