2 Epidemiology of Faecal Incontinence

Introduction

This chapter focuses on the prevalence and incidence rate of faecal incontinence in the general population and specific subgroups, including the elderly and children. Epidemiological definitions are described, and problems with measuring faecal incontinence are discussed. Descriptive studies of prevalence and incidence rates are reviewed, including demographic determinants and the reliability of the prevalence estimates. A thorough discussion of risk factors for the development of faecal incontinence is covered elsewhere in this volume. Having highlighted the need for valid, reliable measurement tools, an exam- ple of such a tool is given for use in epidemiologic studies.

Definitions

The following epidemiologic definitions are used in this chapter:

Prevalence: the proportion of a population with a disease at a specific point in time. This is also called the

“point” prevalence. Prevalence measures are given as proportions, percentages or cases per population.

Incidence Rate: a measure of how rapidly people are newly developing a disease or health status, rep- resented by the number of new cases in a time period divided by the average population in that time peri- od. Although commonly called the “incidence”, this is a true rate, as it measures the number of new diag- noses per population per time period.

Epidemiological Bias: systematic deviation of study results from the true results because of the way in which the study is conducted. This is usually divid- ed into three types of bias: selection bias, information bias and confounding. Table 1 demonstrates the com- mon causes of bias in prevalence studies of faecal incontinence and their likely effect on the prevalence estimate.

Problems with Measurement

Measuring faecal incontinence has long proved diffi- cult for those wishing to study its epidemiology.

When measuring the frequency of faecal inconti- nence in a population, it is necessary to have a clear idea of both the definition and the criteria for diag- nosis. A consistent case definition is vital for data about prevalence and incidence rate to be meaning-

Epidemiology of Faecal Incontinence

Alexandra K. Macmillan, Arend E.H. Merrie

2

Table 1. Sources of bias in prevalence studies of faecal incontinence and their likely effect on the prevalence rate [1]

Source of bias Likely effect

Selection bias

Sample frame Sampling an older population may overestimate prevalence Sampling healthy workers may underestimate prevalence

Sampling general practice or hospital patients may overestimate prevalence Response rate Low response rate is likely to result in an overestimate of prevalence by

self-selection of those with incontinence and a higher proportion of older participants Information bias

Outcome definition Use of an insensitive definition will underestimate the prevalence, and an oversensitive definition may overestimate it

Data collection method Face-to-face or telephone interviewing is likely to underestimate the prevalence, and use

of anonymous postal questionnaires may overestimate the prevalence

ful and comparable. While faecal incontinence is commonly defined as a loss of voluntary control of the passage of liquid or stool, it is usual for clinicians to use this term to include incontinence of flatus. The term “anal incontinence” has also been used to include the uncontrolled passage of flatus and liquid or solid stool. These two definitions can therefore be confusing, and we recommend the continued use of the term “faecal incontinence” to include the incon- tinence of flatus as part of a continuum. Some quali- fication of these definitions with regard to quantity, frequency and impact on quality of life is also required in any assessment of prevalence or inci- dence rate, particularly if such an assessment is to be useful for planning to meet a community need for assessment and treatment services. Rather than a sin- gle disease, faecal incontinence represents a clinical spectrum with diverse manifestations that are closely related to its varied aetiology. This makes classifica- tion within the case definition important. The Rome committees [2–4] have provided useful case defini- tions for functional faecal incontinence that can eas- ily be converted for also defining faecal incontinence with an organic origin.

Some work around definition and classification has been done in the paediatric population in which there is again confusing terminology. There have been several attempts to standardise the definition of functional faecal incontinence in childhood, which accounts for more than 90% of cases [5, 6] The term

“encopresis” is commonly used for paediatric faecal incontinence; however, there is variability about its definition in the literature. In 1994, a “classic” set of criteria was defined for encopresis (with or without symptoms of constipation) [7]. The criteria included two or more faecal incontinence episodes per week in children older than 4 years. The Rome II consensus group also defined criteria for nonretentive faecal incontinence of once per week or more for at least 3 months in a child older than 4 years [6, 8]. However,

these two definitions exclude faecal incontinence secondary to constipation and faecal retention, which account for a significant proportion of cases [5, 6, 9]. In 2004, a consensus conference on faecal incontinence defined encopresis as the repeated incontinence of a normal bowel movement in inap- propriate places by a child aged 4 years or older [9].

Soiling was defined as the involuntary leakage of small amounts of stool, and both encopresis and soil- ing were encompassed in the term faecal inconti- nence. No criteria related to frequency were included in this definition. These definitions are summarised in Table 2.

In addition to the inconsistencies in definition and classification noted above, data relating to morbidity from faecal incontinence is not included in routinely collected data sets (such as emergency hospital admissions or deaths). This lack of routine data results in a reliance on self-reported assessments for accurate epidemiologic measurement. A number of methods can be used to collect such data about the prevalence of faecal incontinence, most commonly by telephone or face-to-face interviews or by postal surveys. These methods can either be anonymous or named. Comparison of data collection methods for faecal incontinence has not been undertaken. How- ever, for other socially sensitive behaviours, the validity of data collected via face-to-face or telephone interviews compared with self-administered surveys has been tested. From this testing, anonymous ques- tionnaires are recommended, as they provide a greater degree of validity than either interview method. These measurement challenges are com- pounded by sufferers’ social stigmatisation and com- munity members’ reluctance to discuss bowel habits in general [10, 11].

In summary, definitions and survey methods sig- nificantly affect the outcomes of studies measuring the frequency of faecal incontinence in the popula- tion. We recommend the use of the term “faecal

Table 2. Definitions of functional paediatric faecal incontinence [1]

Authors Definition Age criterion Frequency criterion

Benninga et al. Encopresis: voluntary/ Older than 4 years On a regular basis

1994 [6] involuntary passage of

normal bowel movement in the underwear (or other unorthodox locations)

Rome II consensus Nonretentive faecal soiling Older than 4 years Once per week for

group 1999 [1] more than 12 weeks

Di Lorenzo and Benninga Encopresis: repeated Older than 4 years None given

2004 [8] expulsion of normal bowel

movement in inappropriate

places

incontinence” that includes incontinence of flatus for both adults and children. Furthermore, anonymous, self-administered questionnaires are the recom- mended survey method for cross-sectional studies of faecal incontinence.

Studies Measuring Disease Frequency

Prevalence in the Adult Population

Several cross-sectional prevalence studies have been undertaken; however, they all used different defini- tions of faecal incontinence, few used anonymous questionnaires and they included different age groups and sample populations. In addition, many of the studies have been hampered by poor response rates. Together, these factors contribute to signifi- cant epidemiological bias within studies, limiting estimate interpretation and making prevalence esti- mates difficult to compare.

This likely explains why the prevalence of faecal incontinence for adults in the community reported in cross-sectional studies varies more than ten-fold.

Thomas et al. [12] reported a prevalence of 0.43%

among general practice patients in the UK but defined faecal incontinence as “faecal soiling twice or more per month” and relied on face-to-face confir- mation of answers to a postal survey. Using a more sensitive definition and an anonymous self-adminis- tered questionnaire, Giebel et al. surveyed hospital patients, employees and their families and found a prevalence of any loss of control of stool, “winds” or frequent faecal soiling of almost 20% [13]. The full range of results found in prevalence studies of com- munity adults is demonstrated in Figure 1.

Four studies that minimised epidemiological bias by using anonymous, self-administered question- naires sampling randomly from the general adult population and achieving a good response rate found a prevalence rate of faecal incontinence ranging from 11% to 17% [14–16]. These studies are summarised in Table 3.

In keeping with a commonly held belief, these studies (Table 3) demonstrated an increasing preva- lence of faecal incontinence with increasing age: up to 25% in those aged over 70 years [14]. However, the studies also examined gender differences in preva-

Fig. 1. Variation in prevalence of faecal incontinence in studies of community-dwelling adults. Reprinted with permission from [1]

De Miguel 1999 Denis 1992 Giebel 1998 Lynch 2000 MacLennan 2000 Nelson 1995 Denis 1992 Drossman 1996 Enck 1991 Johanson 1996 Kalantar 2002 Lam 1999 MacLennan 2000 Perry 2002 Roberts 1999 Roig Vila 1993 Thomas 1984 Thompson 2002

Prevalence and 95% Confidence Interval

26 24 22 20 18 16 14 12 10 8 6 4 2 0

Anal Incontinence Faecal Incontinence

Faecal Incontinence, bias minimised

lence, and contrary to popular belief, there was no clear gender difference. Johanson and Lafferty [14]

and Lam et al. [16] found a higher prevalence in men than in women, Kalantar et al. [15] found no signifi- cant difference between men and women and Siproudhis et al. [17] found a higher prevalence in women (Table 4). Further investigation is required to establish whether there are differences in the fre- quency of faecal incontinence related to other demo- graphic factors, such as ethnicity, occupation or socioeconomic status.

Prevalence in Older Adults

The best-designed prevalence studies of faecal incon- tinence in the general population, discussed above,

have demonstrated an increasing prevalence with increasing age. Indeed, it has previously been assumed that faecal incontinence is limited to elder- ly populations and some women following child- birth. A number of epidemiological studies have therefore focused solely on elderly populations, either community dwelling or in institutional care.

These studies have similar problems with varying definitions of significant incontinence, subject sam- pling, age groups, response rates and data collection methods. Added to these problems is the frequent use of proxy respondents, particularly for those eld- ers in institutions. Perhaps the most reliable estimate results from a study by Talley et al. in 1992 [18]. They used a validated self-administered questionnaire to assess faecal incontinence (among other gastroin- testinal symptoms) in community-dwelling adults 65 Table 3. Prevalence of faecal incontinence in studies that minimised sources of epidemiological bias

Study Population Sample size Data collection Outcome Prevalence

(response method definition (95% confidence

rate) interval)

Johanson and Convenience 586 Anonymous Any involuntary Approximately

Lafferty 1996 sample of general- self-administered leakage of stool 11% (8.5, 13.5)

[14](USA) practice patients questionnaire or soiling of

aged 18–92 undergarments

Lam et al. Random sample 955 (71%) Anonymous postal At least two of: 15% (12.2, 17.8)

1999 [16] of Sydney electoral questionnaire, stool leakage,

(Australia) roll, aged over 18 core questions pad for faecal

validated soiling,

incontinence of flatus >25%

of the time

Kalantar et al. Gender-stratified 990 (66%) Anonymous Unwanted release 11.2% (8.8, 13.7) 2002 [15] random sample of self-administered of liquid or solid

(Australia) Sydney electoral roll, questionnaire faeces at an

aged over 18 inappropriate time

or place

Siproudhis et al. Random stratified 7196 (72%) Anonymous Uncontrolled 16.8% (15.9, 17.6)

2006 [17] cluster sample of self-administered anal leakage

(France) noninstitutionalized postal questionnaire of stool ever

adults aged over 15 in past 12 months

a

Estimated from sample size and response rates stated using a simple random sample assumption of design effect

Table 4. Prevalence of faecal incontinence by gender in least-biased studies where figures were available

Study Prevalence in women Prevalence in men

(95% confidence interval) (95% confidence interval)

Johanson and Lafferty 1996 [14] (USA) 17% 20.5%

Lam et al. 1999 [16] (Australia) 11.1% 20%

Kalantar et al. 2002 [15] (Australia) 11.6% (8.3, 15.0) 10.8% (7.2–14.4)

years and older and found an age-adjusted preva- lence of more than once per week of 3.7%, with 6.1%

of the same population wearing a pad. There was no difference between men and women and no signifi- cant increase in prevalence with age within elders.

This prevalence estimate is somewhat lower than that reported for the oldest subjects in the general popu- lation studies described above. This is likely to be related to a less sensitive definition of incontinence.

Prevalence in the Paediatric Population

There have been very few prevalence studies of child- hood faecal incontinence, and no formal systematic review of epidemiological studies has been undertak- en. Bellman’s seminal epidemiological studies in the 1960s provided a strong basis for more recent work [19]. As with studies of adult faecal incontinence, these prevalence studies used variable definitions of incontinence, soiling and encopresis, as discussed previously. Issues of low response rate and difficul- ties with data collection are made more problematic in children because of the need for parental permis- sion and assistance to take part in research. Faecal incontinence is very distressing for children, and they will often attempt to hide their incontinence from their parents [9]. Parents are often also embar- rassed and distressed by their child’s incontinence, leading to under-reporting [19]. This is likely to result in underestimation of the problem by preva- lence studies. Although the accuracy of parental information about bowel habit has been tested [20], no study has investigated the accuracy of informa- tion from the child alone. All these factors affect the prevalence found by these studies.

Anonymously collected data from a random questionnaire sample of more than 1,000 6- to 9- year-old Danish school children [21] recently sug- gested a prevalence higher than that commonly quoted, with a prevalence of 5.6% in girls and 8.3%

in boys. However, no definition of faecal inconti- nence was given. A more recent population-based study of school children (aged 5–6 and 11–12 years) defining encopresis as the involuntary loss of faeces in the underwear once a month or more was report- ed [22]. Parents were asked about the presence of encopresis on behalf of the child in a face-to-face interview with a doctor while the child was present.

The authors reported a prevalence of 4.1% in 5- to 6-year-old children and 1.6% in the 11- to 12-year- old children, with a significantly greater prevalence in boys than in girls. Further demographic associa- tions were identified in the study. In particular, the

prevalence of encopresis was significantly higher in children of lower socioeconomic status. These stud- ies demonstrate potential information bias, with the lack of definition in one and method of data collec- tion in the other being likely to underestimate the prevalence.

Incidence-rate Studies

There are no true incidence-rate studies of faecal incontinence in the general population. This dearth of research is a result of the difficulties with meas- urement discussed above. The incidence rate of fae- cal incontinence is therefore not known. As a result, the natural history of faecal incontinence in the gen- eral population is likewise unclear, in particular with regard to rates of spontaneous remission.

Conclusion

In conclusion, the prevalence of faecal incontinence in the general population is poorly understood. From the available studies, it is likely that the prevalence is between 11% and 17%, which is higher than usually quoted. This appears similar for both genders and increases with age. There is some indication that the prevalence of faecal incontinence also varies by socioeconomic status and ethnicity. In children, there have been too few well-designed studies to esti- mate a prevalence range; however, it is likely to be higher than that normally quoted for the reasons dis- cussed above.

For future epidemiologic studies, a consensus def- inition of faecal incontinence is recommended that includes any incontinence of flatus, liquid stool or solid stool that impacts on quality of life in adults and children [1]. Any further prevalence studies should ideally be undertaken using anonymous self- administered questionnaires to aid with minimising bias. Widespread use of a standardised questionnaire would assist with achieving consistency and compa- rability between further studies. An example of a standardised, valid and reliable self-administered questionnaire [23] is included (Appendix). This questionnaire was constructed and validated in New Zealand, and incorporates with permission the Bris- tol Stool Form Scale [24–26], Faecal Incontinence Severity Index (with patient weighted scoring) [27]

and Faecal Incontinence Quality of Life Index (scored as per Rockwood et al. [28]).

Continued

Appendix

BOWEL CONTROL QUESTIONNAIRE

The first section relates to general information, and will help with our data analysis.

1. What is your gender? (Please tick one) Female

Male

2. What is your age in years?

3. Which of these ethnic groups do you identify with most? (Please tick the box or boxes that apply to you)

NZ European

Maori

Samoan

Tongan

Cook Island Maori

Niuean

Chinese

Indian

Other

(such as Tokelauan, Japanese) Please state:

Go to next page

4. What is your highest level of education? (Please tick one)

No formal qualification

School Certificate

University Entrance (e.g. Bursary)

Trade/Professional Diploma of Certificate

Bachelor’s Degree

Postgraduate Degree

5. What is your occupation?

(e.g. primary school teacher, homemaker/caregiver, motel manager, clothing machinist)

If retired or currently unemployed, please also state most recent occupation

Go to next page

The following questions relate to your usual bowel habit in the last 3 months.

6. On average, how often did you pass a bowel motion in the past 3 months?

(Please tick one)

More than 3 times per day

2 to 3 times per day

Once per day

2 to 3 times per week

Once per week

Less than once per week

7. What has been the usual consistency of your bowel motions in the past 3 months?

(Please circle the ONE type that applies to you USUALLY)

Go to next page Type Description

1 Separate hard lumps like nuts (difficult to pass) 2 Sausage shaped but lumpy

3 Like a sausage but with cracks on its surface

4 Like a sausage or snake, smooth and soft

5 Soft blobs with clear-cut edges (passed easily)

6 Fluffy pieces with ragged edges, a mushy stool

7 Water, no solid pieces, ENTIRELY LIQUID

The next question relates to any difficulty you may have had passing a bowel motion in the past 3 months.

8. In the past 3 months have you experienced any of the following? (Please tick all that apply to you)

Straining on more than 1 out every 4 bowel motions

Feeling that your bowel motion is incomplete more than a

quarter of the time

Feeling of blockage during bowel motions more than a

quarter of the time

Need to use fingers or hands to help with passing a bowel motion more than a quarter of the time

None of the above statements apply to me

9. In the past 3 months have you used medications regularly, including laxatives or antidiarrhoeal medication, to help you pass a bowel motion?

Yes

No

Go to next page

Go to next page

The following section relates to any amount of bowel leakage (accidental loss of gas, mucus or stool/faeces) you may have had in the last month.

10. For each of the following, please mark on average how often in the past month you experienced any amount of bowel leakage.

(Ngati Whatua translations are given in brackets)

PLEASE TICK ONE BOX IN EACH ROW

Never 1 to 3 Once a 2 or Once a 2 or

times week more day more

a times times

month a week a day

A. LEAKAGE OF

GAS

(tete)

B. LEAKAGE OF

MUCUS

(para tutae) C. LEAKAGE OF

LIQUID STOOL

(tikotiko) D. LEAKAGE OF

SOLID STOOL

(puru tutae)

11. How often in the past month did you wear a pad because of bowel leakage?

2 or more times a day

Once a day

2 or more times a week

Once a week

1 to 3 times a month

Never

12. In the past month, did you have any warning or feeling when you needed to pass a bowel motion?

Yes

No
(Go to question 13) If Yes, did you have to rush/hurry to reach the toilet as soon as you felt the need to pass a bowel motion?

Yes

No

13. In the past month, did you ever have bowel leakage shortly after emptying your bowels or passing a bowel motion?

Yes

No

The following question relates to your bladder control in the past month.

14. In the past month have you experienced loss of control of your bladder

(a) on coughing, laughing, sneezing or other physical activity?

Yes

No

(b) when feeling an urgent need to pass water (urinate), but not making it to the toilet in time?

Yes

No

Go to next page

Go to next page

The next questions are only for women. If you are male Go to Question 22 on the next page.

15. How many children have you given birth to?

If you have had no children Go to Question 21.

16. Thinking back on these births, how many were vaginal deliveries?

17. In your longest labour, how long did you push for (second stage)? (Please tick one)

Less than 1 hour

1 to 2 hours

More than 2 hours

18. Thinking back on all your labours, were forceps or instruments ever used?

Yes

No

19. Thinking back on all your labours, did you ever have a tear or episiotomy involving the muscles of your anus (back passage)?

Yes

No

20. Thinking back on all your labours, what was the weight of your largest baby?

kg OR lbs

21. Have you ever had a hysterectomy (operation to remove your womb)?

Yes

No

If yes, was it... Vaginal

Abdominal

Go to next page The following questions are for everyone.

22. Have you ever had any of the following types of surgery to your bowels or anus (back passage)? (Please tick all that apply to you)

Removal and rejoining of party of your bowel

Anal fistula surgery

Operation on anal muscles

Operation for haemorrhoids or piles

Major prostate operation

None of the above

23. Do you have a stoma (bag) for emptying your bowels?

Yes

No

24. Have you ever injured your anus (back passage), not including during labour?

Yes

No

25. Do you suffer from any of the following medical problems? (Please tick all that apply to you) Inflammatory bowel disease

(Eg Crohn’s disease or ulcerative colitis)

Irritable bowel syndrome

Rectal prolapse

Diabetes

Stroke

Other neurological condition

Decreased mobility

None of the above apply

Go to next page The following section relates to how your bowel habit may be affecting your lifestyle.

26. In general, would you say your health is:

Excellent

Very Good

Good

Fair

Poor

27. For each of the items below, please indicate by circling the appropriate number, how much of the time the item is a concern for you due to any accidental bowel leakage (gas, liquid, solid or mucus). If it is a concern for you for another reason (not accidental bowel leakage), then please circle “None of the time”.

PLEASE CIRCLE ONE NUMBER IN EACH ROW

Most Some A little None Not

of the of the of the of the Applicable Because of accidental bowel leakage: time time time time

I am afraid to go out 1 2 3 4 N/A

I avoid visiting my friends 1 2 3 4 N/A

I avoid staying overnight away from home 1 2 3 4 N/A

It is difficult for me to get out and do things 1 2 3 4 N/A

like going to a movie or to church

I cut down on how much I eat before I go out 1 2 3 4 N/A

Whenever I am away from home, I try and 1 2 3 4 N/A

stay near a toilet as much as possible

It is important to plan my daily activities 1 2 3 4 N/A

around my bowel habit

I avoid travelling 1 2 3 4 N/A

I worry about not being able to get to the 1 2 3 4 N/A

toilet in time

I feel I have no control over my bowels 1 2 3 4 N/A

I can’t hold on to my bowel motion long 1 2 3 4 N/A

enough to get to the bathroom

I try to prevent bowel accidents by staying 1 2 3 4 N/A

very near a bathroom

Go to next page

28. Because of any accidental bowel leakage, please indicate, by circling one number in each row, how much you agree or disagree with each of the following statements.

If it is a concern for you for another reason, or not a concern at all, please circle N/A.

PLEASE CIRCLE ONE ANSWER IN EACH ROW

Due to accidental bowel Strongly Somewhat Somewhat Strongly Not

leakage: agree agree disagree disagree Applicable

I feel ashamed 1 2 3 4 N/A

I cannot do many things I want to do 1 2 3 4 N/A

I worry about bowel accidents 1 2 3 4 N/A

I feel depressed 1 2 3 4 N/A

I worry about the smell 1 2 3 4 N/A

I feel unhealthy 1 2 3 4 N/A

I enjoy life less 1 2 3 4 N/A

I have sex less often than I would like 1 2 3 4 N/A

I feel different from other people 1 2 3 4 N/A

The possibility of bowel 1 2 3 4 N/A

accidents is always on my mind

I enjoy life less 1 2 3 4 N/A

I am afraid to have sex 1 2 3 4 N/A

I avoid travelling by plane or 1 2 3 4 N/A

public transport

I avoid going out to eat 1 2 3 4 N/A

Whenever I go somewhere new,

I make sure I know where the 1 2 3 4 N/A

toilets are

29. During the past month, have you felt so sad, discouraged, hopeless, or had so many problems that you wondered if anything was worthwhile?

Extremely so- to the point where I have just about given up

Very much so

Quite a bit

Some- Enough to bother me

A little bit

Not at all

30. Have you ever discussed loss of bowel control with anyone? (Please tick all that apply to you)

YES Family

Family Doctor

Specialist

Other health professional

Please say what kind of health professional . . . .

NO

31. Have you been referred to any other service for loss of bowel control?

Yes
Please say where . . . .

No

This is the end of the questionnaire.

Thank you for your time and assistance.

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