Prevalence of idiopathic fecal incontinence in a community-based sample.

Background: The epidemiology of fecal incontinence (FI) remains incompletely understood. The use of different interview questions in highly selected populations has resulted in widely varying reported rates.

Aim: To define the prevalence of idiopathic FI in a Canadian urban community sample using a validated interview questionnaire.

Methods: Respondents completed a telephone interview regarding bowel health as part of the 2006 Winnipeg Area Study (WAS). The WAS has been conducted annually by the Department of Sociology at the University of Manitoba (Winnipeg, Manitoba) since 1981. The household was the primary sampling unit. An eligible respondent was an individual 18 years of age or older who lived at that address, matched a randomly preassigned sex and provided consent. Respondents were asked whether they had ever been diagnosed by a physician with colon cancer, ulcerative colitis, Crohn's disease or irritable bowel syndrome. They were also asked, 'In the past 12 months have you experienced accidental leakage of liquid or solid stool?' Respondents were asked not to consider short-term diarrheal illness. Finally, respondents were asked to rank eight attributes of bowel habit on a 10-point scale. Answers ranking 5 points or greater were defined as having the attribute.

Results: In the city of Winnipeg, population 650,000, 1153 households were contacted. Of these, 727 (63%) agreed to participate and formed the study sample. Of the respondents, 361 were men and 366 were women (mean age 47 years). The sociodemographics of these respondents were comparable with those reported in previous WAS samples and the 2001 Canadian census data. Respondent cooperation, high interview quality and willingness for repeat contact were rated by the interviewers at 93%, 89% and 90%, respectively. FI was reported by 3.7% of the sample. There was no difference in sex or age of those reporting FI when compared with the rest of the sample. With physician-diagnosed gastrointestinal conditions removed from the analysis, 2.0% of the sample reported FI. Of the gastrointestinal conditions, only irritable bowel syndrome demonstrated a significant correlation with FI (one-sided X(2) test 11.567, degrees of freedom = 1; P=0.001). Four bowel habit attributes demonstrated strong correlation with FI (P=0.0001 for each t test): admission to any type of bowel accident, inability to delay toileting, inability to control passage of stool and need to wear a pad due to soiling. These four bowel habit attributes were reported (ranked 5 points or greater) by 1.5%, 22%, 2.4% and 1.5% of the sample, respectively.

Conclusion: The prevalence of idiopathic FI in a well-defined community sample was 2.0%. There was no sex preference and the mean age of affected individuals was 47 years - demographic variables that did not vary among the sample. These findings suggest the need to develop a new paradigm beyond aging and childbirth injury to study the pathophysiology of FI. It is imperative to control for subjects with known irritable bowel syndrome in epidemiological studies because their inclusion in the present analysis doubled the calculated prevalence of FI.