AIM: To determine effect of irritable bowel syndrome (IBS) subtype on IBS-specific quality of life (QOL) questionnaire and its subscales.

METHODS: We studied IBS patients visiting our functional gastroenterology disorder clinic at a tertiary care center of Unites States. IBS and IBS subtype were diagnosed using Rome-III questionnaire. QOL was assessed using IBS-QOL questionnaire. IBS-QOL assesses quality of life along eight subscales: dysphoria, interference with activities, body image, health worry, food avoidance, social reactions, sexual health, and effect on relationships. IBS-QOL and its subscales were both scored on a range of 0-100 with higher scores suggestive of better QOL. Results of overall IBS-QOL scores and subscale scores are expressed as means with 95%CI. We compared mean IBS-QOL score and its subscales among various IBS-subtypes. Analysis of variance (ANOVA) was used to compare the mean difference between more than two groups after controlling for age and gender. A post-hoc analysis using Bonferroni correction was used only when P value for ANOVA was less than 0.05.

RESULTS: Of 542 patients screened, 243 had IBS as per Rome-III criteria. IBS-mixed (IBS-M) was the most common IBS subtype (121 patients, 49.8%) followed by IBS- diarrhea (IBS-D) (56 patients, 23.1%), IBS-constipation (IBS-C) (54 patients, 22.2%) and IBS-unspecified (IBS-U) (12 patients, 4.9%). Overall IBS-QOL scores were significantly different among various IBS-subtypes (P = 0.01). IBS-QOL of patients with IBS-D (61.6, 95%CI: 54.0-69.1) and IBS-M (63.0, 95%CI: 58.1-68.0) was significantly lower than patients with IBS-C (74.5, 95%CI: 66.9-82.1) (P = 0.03 and 0.02 respectively). IBS-D patients scored significantly lower than IBS-C on food avoidance (45.0, 95%CI: 34.8-55.2 vs 61.1, 95%CI: 50.8-71.3, P = 0.04) and interference with activity (59.6, 95%CI: 51.4-67.7 vs 82.3, 95%CI: 74.1-90.6, P < 0.001). IBS-M patients had more interference in their activities (61.6, 95%CI: 56.3-66.9 vs 82.3, 95%CI: 74.1-90.6, P = 0.001) and greater impact on their relationships (73.3, 95%CI: 68.4-78.2 vs 84.7, 95%CI: 77.2-92.2, P = 0.02) than IBS-C patients. Patients with IBS-M also scored significantly lower than IBS-C on food avoidance (47.2, 95%CI: 40.7-53.7 vs 61.1, 95%CI: 50.8-71.3, P = 0.04) and social reaction (66.1, 95%CI: 61.1-71.1 vs 80.0, 95%CI: 72.1-87.7, P = 0.005).

CONCLUSION: IBS-D and IBS-M patients have lower IBS-QOL than IBS-C patients. Clinicians should recognize food avoidance, effects on daily activities and relationship problems in these patients.

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by abdominal pain or discomfort and alteration of bowel habits in the absence of an organic disorder[1-4]. It is the most common gastrointestinal disorder, affecting between 4%-22% of general population[1-4]. IBS is a generally non life-threatening disorder that is not associated with decreased life expectancy, which may potentially lead clinicians to underestimate its impact on patients’ lives and the healthcare system as a whole[5]. Nevertheless, studies have shown that patients with IBS make two to three times the number of health care visits per year compared to age-matched controls[6-8]. Additionally, many studies have also shown that patients with IBS have poorer quality of life (QOL) when compared to the general population as well as patients with other chronic diseases such as diabetes and end stage renal disease[8,9]. QOL has also been shown to correlate with disability, healthcare resource utilization, and clinical response to treatment. Thus, it is important to understand the variables affecting the QOL in patients with IBS[10].

While QOL in IBS has been shown to be affected by extraintestinal symptoms, psychiatric symptoms, disease severity, and gender, the effect of IBS-subtype is unclear[10,11]. Previous studies studying the effect of IBS subtype on QOL have failed to show any difference[11-15]. Most of these studies used general health-related QOL questionnaires like the SF-36 and WHO-QOL, which do not capture the specific issues pertinent to IBS[11-14]; thus, these general questionnaires could have minimized the impact of gastrointestinal symptoms on overall QOL. Disease-specific instruments have been developed and validated for IBS, such as the QOL measure specific to IBS (IBS-QOL), the IBS QOL questionnaire, and the functional digestive disorder QOL questionnaire[15-18]. These questionnaires aim to address the specific QOL domains that are most heavily affected by IBS, yet there is a paucity of data on effect of IBS subtype on IBS-QOL.

In order to better understand the interactions between IBS subtype and IBS-QOL, we studied the impact of IBS subtype on disease-specific QOL using the IBS-QOL questionnaire in our cohort of IBS patients.

Two hundred fifty one of 572 patients screened during the study period were diagnosed with IBS. The mean age of the study population was 44.3 years. More than three-fourths of the patients (79.7%) were females (200 females, 51 males). Eight patients who were diagnosed with IBS did not have sufficient information to classify them into subtypes. Of the remaining 243 patients, IBS-mixed type (IBS-M) was the most common subtype (121 patients, 49.8%), followed by IBS-diarrhea (IBS-D) (56 patients, 23.1%), IBS-constipation (IBS-C) (54 patients, 22.2%), and IBS-unspecified (IBS-U) (12 patients, 4.9%). For the purpose of statistical analysis, patients with IBS-U were excluded given their small sample size in addition to the uncertainty of what IBS-U category means clinically.

In this analysis of IBS patients presenting for evaluation at a tertiary care clinic, we found that IBS-D and IBS-M patients have a significantly-worse disease-specific QOL than IBS-C subtype. IBS-D patients also have more interference with their daily activities and avoided food more commonly when compared to patients with IBS-C. Similarly, patients with IBS-M also had more interference in their activities, greater impact on their relationships and lower social reaction score than IBS-C patients. To our knowledge, this data is unique in demonstrating subtype-specific QOL differences in this population.

Most of the previous studies studying the effect of IBS subtype on QOL failed to show any difference in QOL between the subtypes[12-15,18,21-23]. Like our study, most of these studies are from tertiary healthcare settings and have comparable sample sizes. However, most of these studies used general health-related QOL questionnaires like the SF-36 and WHO-QOL[11,12,14,22,24]. The use of such general QOL questionnaires could have minimized the impact of gastrointestinal symptoms on overall QOL. Our study used IBS-QOL, which captures the specific concerns of patients with IBS.

Notably, other studies using IBS-QOL have failed to show similar differences when IBS-QOL is compared by IBS subtype[15,21,25]. All three of these studies analyzed patients from outside the United States and therefore may be examining a slightly-different IBS population than our own. In line with our results, Patrick et al[18] and Schmulson et al[23] also found lower IBS-QOL scores in United States patients with IBS-D and IBS-M compared to those with IBS-C, but these differences failed to reach statistical significance. Both these studies enrolled fewer IBS patients than ours.

By overall IBS-QOL and all eight individual subscale scores, IBS-D and IBS-M were very similar to each other and distinct from IBS-C patients. Mearin et al[26] previously reported that many patients with IBS-D or IBS-C may qualify for the diagnosis of IBS-M over time. It is possible that these mixed patients were more similar to IBS-D patients than those with IBS-C in our population. Others have reported similarities between IBS-M patients and IBS-D in terms of defecation urgency, which at least partly explains low subscale scoring in the food avoidance and interference with activity domains in patients with IBS-M[14].

We found that patients with IBS-D and IBS-M had significantly more food avoidance when compared with IBS-C patients. Many patients with IBS attribute their gastrointestinal symptoms to diet and - as a result - a majority of patients restrict the consumption of perceived culprit foods[27]. Self-reported food avoidance has also been associated with high symptom burden and a reduced QOL[28]. Studies have shown that fermentable carbohydrates could increase colonic gas production, small intestinal water volume, and small intestinal motility and thus exacerbate IBS symptoms like pain, bloating, and diarrhea. In fact, fasting and diets restricted in fermentable carbohydrates were demonstrated to improve gastrointestinal symptoms including pain, bloating, and diarrhea in patients with IBS[29-31]. Thus, significantly higher food avoidance in IBS-D patients could be result of self- or physician-advised restriction to minimize these gastrointestinal symptoms.

IBS is known to interfere with the physical aspects of health-related QOL including daily activities and work productivity[11,32,33], yet limited data is available on the effect of IBS subtype on daily activities. In our study, patients with IBS-D and IBS-M had significantly more interference with their activities because of their disease than other IBS subtypes. Schmulson et al[23] also reported similar findings in female patients with IBS. Increased bowel frequency could understandably limit the ability of individual to go out and thus engage in daily activities like work, travel, and other social/leisure activities.

Thus, bowel frequency appears to be an important determinant of physical activity domain of QOL. This is further confirmed by the observation that the 5HT3-receptor antagonist alosetron, which improves stool consistency and frequency in these patients, also improved physical activity and work productivity[34]. This data argues that clinicians should focus on adequately controlling diarrheal symptoms in IBS-D patients in addition to addressing the pain and abdominal discomfort that are the hallmarks of IBS.

We found that IBS had a significantly greater impact on relationships in IBS-M patients when compared to IBS-C patients. Silk[33] reported that about one-fifth of married or cohabitating IBS patients reported difficulties in personal relationships due to their illness. More than half also reported embarrassment at the workplace. Interpersonal problems are reported to be more pronounced IBS-D patients[35]. Psychodynamic interpersonal therapy and improvement in interpersonal difficulties have not only been shown to improve psychological distress but also overall health status in patients with IBS[36]. Thus, patients with IBS-M might be benefit from counseling and interpersonal therapy.

Our study has some limitations. We did not study other factors known to affect the QOL in IBS such as somatic comorbidities, psychiatric comorbidities, and disease severity - which could have confounded our results. As a surrogate of gastrointestinal symptom severity, PAGI-SYM was used in our study as it is routinely administered to every patient coming to our functional gastrointestinal disorder clinic. Although PAGI-SYM has not been validated as a measure of symptoms severity in IBS patients, the components of the PAGI-SYM score, including bloating, lower abdominal pain, upper abdominal pain, and early satiety are all domains used to assess IBS symptom severity in IBS severity scales[37].

We found that overall PAGI-SYM score as well as individual subcomponent scores did not differ significantly among IBS subtype, suggesting similar disease severity amongst patients in our study population. The sample size of our study was also small, and similar studies should be repeated on larger number of IBS patients. Because these findings are derived from patients attending a tertiary care center, our study may not be easily generalized to IBS patients seen in community gastrointestinal practices or in the primary care setting. However, clinicians in these settings should also pay attention to these QOL domains.

We demonstrated that IBS-D and IBS-M patients have an overall lower IBS-QOL than IBS-C patients. Clinicians should pay special attention to patient-reported food avoidance, interference with daily activities, social reactions and problems with relationships, which are more prominent in IBS-D and IBS-M than other subtypes patients and drive a lower disease-specific QOL.