Prevalence of faecal incontinence and associated risk factors

Faecal incontinence is a significant cause of social embarrassment and imposes a high cost on the patient and the community. It can be physically and psychologically disabling, leading to progressive isolation and a devastating social impact. It is the second most common cause for institutionalisation of the elderly in the USA,2,3 and accounts for costs of over US$400 000 000 per year for adult diapers.4 Borrie et al estimated that the annual cost of incontinence for an institutionalised patient in Canada was C$9771.5 Patients suffering from faecal incontinence may be reluctant to seek medical advice,6,7 and doctors may be reluctant to ask about the condition.

Reports of the prevalence of faecal incontinence in the community have shown significant variability.1,8-13 An accurate estimation of the magnitude of the problem in the community would help in providing knowledge of who is at greatest risk so that preventive measures can be applied. For this reason, we undertook a population-based study of the epidemiology of faecal incontinence, using a self-administered questionnaire. We aimed to ascertain the prevalence of faecal incontinence in the community sample, evaluate the health-seeking behaviour in people afflicted by faecal incontinence, determine its associated risk factors, and assess the impact of the condition on quality of life.

This study was formally approved by the Wentworth Area Health Service's ethics committee. The samples were drawn randomly from the Lindsay electoral roll, an electoral region in western Sydney, Australia. Since voting is compulsory for all citizens 18 years and over in Australia, the Electoral Commission in each State routinely registers and updates the lists of citizens in each electorate. The population sampling frame is demographically similar to the Australian population, except that its inhabitants are slightly younger and have a slightly higher socioeconomic status.14 The survey consisted of a self-administered questionnaire sent out to 990 residents in two stages in 1997 and 1998 (stratified for equal numbers of men and women).

Most of the questionnaire items had been previously validated in Australian and US populations.14-16 Two forms of the questionnaire were used. A long form, consisting of 32 questions, assessed bowel habit, laxative use, presence and severity of faecal incontinence, previous suspected risk factors for faecal incontinence, health-seeking behaviour, degree of mobility, and social impact of faecal incontinence (n = 770 subjects). A short form, with seven questions on a single page, was a pruned version of the longer questionnaire, primarily aimed to assess the presence of faecal incontinence (n = 220 subjects). In the first stage, 440 questionnaires were sent out (220 short and 220 long). In the second stage, long questionnaires were mailed to a further 550 randomly selected residents. We used the two questionnaire formats to evaluate which would be optimal in achieving higher response rates (results reported elsewhere).17

All the mailouts included a reply-paid envelope and covering letters explaining the purpose of the study, with the investigators' contact number. The respondents were assured that their responses were confidential.

After the first mailout, a second mailout was sent at four weeks to those who had not returned their questionnaires. A third mailout for those who did not respond was sent out after a further six weeks. Six weeks after the third mailout we followed up non-responders by telephone if we could find their phone number. The second and third mailouts included a refusal form so that subjects could, if they wished, use the reply-paid envelope to indicate that they did not want to be contacted again.

We defined faecal incontinence as an involuntary loss of anal sphincteric control that led to unwanted release of liquid or solid faeces (not flatus) at an inappropriate time or in an inappropriate place. Symptoms were measured over the past 12 months, the standard time frame in our previously validated questionnaires.15 Faecal incontinence related to an acute illness (eg, acute diarrhoea) was excluded. Quality of life was measured by asking about interference with social activities or lifestyle.15 We also enquired about perceived level of health, mobility and independence.

An overall response rate of 66% (651 out of 990) was achieved. The age and sex distribution of responders and non-responders was similar.

Faecal incontinence was reported by 72 of 642 responders (incomplete data for nine responders), yielding a prevalence of 11.2% (95% CI, 8.8%–13.7%). This was similar among men (31/286 [10.8%]; 95% CI, 7.2%–14.4%) and women (41/353 [11.6%]; 95% CI, 8.3%–15.0%). The prevalence of solid and liquid faecal incontinence was 2.0% (13/642; 95% CI, 0.9%–3.1%) and 9.0% (58/642; 95% CI, 6.8%–11.3%), respectively. Liquid faecal incontinence was reported by 8.8% of women (31/353; 95% CI, 5.8%–11.7%) and 9.4% of men (27/286; 95% CI, 6.1%–12.8%); solid faecal incontinence was reported by 1.1% of women (4/353; 95% CI, 0.03%–2.2%) and 3.1% of men (9/286; 95% CI, 1.1%–5.2%). The mean age of subjects with faecal incontinence was 53 years; 55% were women. Faecal incontinence was positively associated with age (χ2 = 11.75; P = 0.003) (Box 1).

Of the 58 people who reported liquid faecal incontinence, 37 (63.7%; 95% CI, 51.4%–76.2%) reported that they usually leaked a small amount, and 21 (36.2%; 95% CI, 23.8%–48.6%) reported that they usually leaked a moderate or large amount. Twelve of the 13 people who reported solid faecal incontinence indicated that this involved a small amount of leakage.

Twenty of 71 people reporting faecal incontinence (incomplete data for one responder) reported having one or more leakages per week (28.2%; 95% CI, 17.7%–38.6%).

This study evaluated the prevalence of faecal incontinence in a random population sample with previously validated, self-administered questionnaires. An acceptable response rate of 66% was achieved and there was no evidence of response bias. The prevalence of faecal incontinence is likely to depend on the definition applied as well as the duration and type of faecal incontinence (solid versus liquid or gas incontinence). Our definitions were easy to understand and clear. We enquired about unwanted release of faeces (excluding flatus) over a defined 12-month period, and excluded faecal incontinence related to acute illness.

Daily or weekly episodes of faecal incontinence have previously been reported to occur in about 2% of the adult population and in about 7% of healthy independent adults over the age of 65.1,4,10 Community-based studies have shown prevalence rates of up to 16.9% in very old, independently living people.1,8,9,11,12,18,19 In this study, the prevalence was 11.2% — higher than in some previous community-based studies,1,8,11 but consistent with more recent studies12,13 (Box 3). The reason for this disparity may lie with the definition used as well as the study methodology. For example, Nelson et al used a telephone interview with a member of the household that asked about the health status of other household members.1 This method potentially underestimates the prevalence of faecal incontinence. Our random population sample should more realistically represent the community prevalence.

We found that the prevalence of faecal incontinence was similar in men and women (10.8% and 11.6%, respectively). Faecal incontinence has traditionally been thought to be more common in women,1,12,20 in part because obstetric trauma can result in unrecognised damage during childbirth. Obstetric injury to the pudendal nerve or sphincter muscle has been proposed as a primary risk factor for faecal incontinence.21,22 Irritable bowel syndrome, which is also more common in women, may be another risk factor.23 A few community-based studies show a higher prevalence of faecal incontinence in women,1,12,20 but others have shown a similar or even higher prevalence in men.8,11,13

Other causes of faecal incontinence are thought to include anal surgery, neurological disease and previously corrected congenital anorectal malformations.24,25 In our study, the prevalence of faecal incontinence was associated with advancing age as well as perianal surgery and injury. However, the prevalence of faecal incontinence was not significantly associated with diabetes or pelvic radiotherapy. Passage of loose or watery stool and urgency were all associated with faecal incontinence, suggesting that diarrhoea can overwhelm the mechanisms involved with maintaining continence. Feelings of incomplete rectal evacuation were also associated with incontinence, but straining was not. While feelings of incomplete defecation, possibly due to pelvic outlet obstruction, may seem to be a counterintuitive risk factor, faecal incontinence associated with faecal impaction and overflow incontinence is well described.26 An association between constipation and faecal incontinence has also been previously shown, which may be caused by pelvic nerve damage in this group of patients.27

Only nine of 33 individuals with faecal incontinence reported seeking medical attention (27.3%); only seven of 48 (14.6%) reported being asked about faecal incontinence by their medical practitioner. Johanson, on surveying patients during doctor visits, reported that 34% discussed their incontinence with the doctor.4 It is likely that patients visiting their doctors are a selected group. Enck et al have reported a systematic underestimation of faecal incontinence, finding that only 5% of patients with faecal incontinence, regardless of the underlying mechanism, had incontinence symptoms noted in the medical charts.6 It is not clear whether the lack of acknowledgement of faecal incontinence was mainly due to the patient's failure to volunteer the information or medical practitioners' reluctance to ask about it.

Many people with incontinence may not seek medical attention owing to the embarrassment associated with this condition, but medical practitioners may be even less likely to ask about this problem. This lack of interest may be because healthcare providers feel that little can be done for these patients other than antidiarrhoeal agents and diapers. With the advent of newer treatments, including surgical techniques and biofeedback,28 and professional awareness programs, doctors may usefully become more involved by asking directed questions about faecal incontinence.

About a third of people reporting faecal incontinence reported some interference with their lifestyle, and faecal incontinence was associated with lower levels of overall health. Whether this is a cause or effect relationship is unclear, but the data suggest that individuals afflicted by faecal incontinence face a number of problems because of the condition.

In conclusion, this study indicates that faecal incontinence is common in the Australian community. It is equally prevalent in men and women and is not confined to the elderly. It is associated with poorer health status and limits the social activities of affected individuals. Despite significant associated morbidity, faecal incontinence appears to be largely unrecognised by health care providers.

1: Prevalence of faecal incontinence according to age and sex