Among this cohort of 2,106 racially diverse females, fecal incontinence was found to be as common as many chronic medical conditions. Nearly one-quarter of females in this cohort reported fecal incontinence in the previous year with nearly 6 percent reporting at least monthly fecal incontinence. Almost one-half of the females with monthly fecal incontinence were moderately or greatly bothered by it, and all females with daily fecal incontinence reported that they were greatly bothered by their condition. Even for females with infrequent fecal incontinence (less than monthly), nearly one-quarter of females had a high level of bother. In addition, fecal incontinence was independently associated with diminished general quality of life, with a greater impact on mental health compared with physical health. Flatal incontinence was much more common than fecal incontinence, with almost three times as many females reporting leakage of gas. The loss of gas, which often is included in studies of anal incontinence, needs to be examined further because the prevalence, frequency, quality of life, and level of bother of flatal incontinence are poorly defined.
The diversity of our large population-based RRISK cohort provides a unique opportunity to examine differences in fecal incontinence among four major racial/ethnic groups within one study. To the best of our knowledge, ours is the first population-based study to ascertain fecal incontinence that includes all major racial/ethnic groups, and thereby avoids the problems inherent in comparing fecal incontinence prevalence across studies. We found that Latina females reported the lowest prevalence, followed by Asian–American, African–American, and non-Latina white females. Latina females remained at the lowest risk for fecal incontinence, even after we adjusted for common risk factors. Interestingly, in the RRISK cohort, Latina females had the highest prevalence of weekly or greater urinary incontinence, followed by white, African–American, and Asian–American females (36, 30, 25, and 19 percent, respectively, P
The decreased prevalence of FI and increased prevalence of urinary incontinence in Latinas could be a result of reporting bias or other unmeasured factors not included in our analysis. Future studies of prevalence using larger sized Latina populations and anorectal physiology studies pertaining to FI in Latinas may further clarify this new finding. Unfortunately, most studies to date have not addressed issues of race and ethnicity and, therefore, data are limited.1,3-6,19
Two studies comparing the prevalence of fecal incontinence between racial/ethnic groups have evaluated only whites vs
. African–Americans, and observed no significant difference in prevalence.10,11
The etiology of fecal incontinence may be better understood with studies that investigate if there are any racial/ethnic disparities in the prevalence of and risk factors for fecal incontinence.
We identified several other independent risk factors for fecal incontinence in the previous year, including obesity, COPD, irritable bowel syndrome, urinary incontinence, and colectomy. In addition, when we examined factors independently associated with monthly or more frequent fecal incontinence, age, diabetes, parity, and cholecystectomy also were significant. These risk factors likely contribute to FI via
multiple mechanisms: anatomic, neurologic, congenital, and functional.12
Mechanistically, fecal incontinence results from an imbalance of the propulsive forces of stool with the resistive mechanisms of the pelvis. Associations of certain conditions with increased abdominal pressure (obesity and coughing related to COPD), increased intestinal motility or loose stool (irritable bowel syndrome, diabetes, colectomy, cholecystectomy), and sphincter or pelvic floor weakness from an anatomic defect or nerve damage (age, parity, diabetes) may all contribute to fecal incontinence.
Increased abdominal pressure is a potential mechanism for the increased FI seen with obesity and COPD. The association of FI with increasing obesity has been described in previous studies4,20
; however, the wide range of BMI in this study allows for more precise estimates of its independent association. We postulate that excess weight increases abdominal and pelvic pressure both at rest and with exertion, which in turn damages pelvic floor support, leading to FI. It is unknown whether this effect is reversible. Independent of smoking, COPD was associated with a nearly twofold higher odds of FI. It is possible that chronic cough caused by COPD also increases pelvic pressure and damages the pelvic floor structures in a similar way as obesity.
Liquid stool associated with increased intestinal motility has been observed by others as an independent predictor of fecal incontinence.10
Diarrhea has been noted in patients with diabetes,21-23
irritable bowel syndrome,24
and those who have had previous cholecystectomy25
Previous studies of FI have examined associations with diabetes and irritable bowel syndrome,4,11,23
and our study additionally found cholecystectomy and colectomy to be associated with FI. If the diarrhea and increased motility associated with these conditions could be treated, it might be possible to decrease the frequency of or eliminate FI in these patients.
Theoretically, weakness of the pelvic floor muscles and support associated with advancing age and parity may impair the resistive forces of the pelvis that prevent leakage of stool. Although some studies have reported that age1,4
are independently associated with fecal incontinence, our study did not. Whereas vaginal delivery often is considered a risk factor for fecal incontinence, it did not remain one in our multivariate analysis. Additionally, both cesarean section and vaginal delivery were associated with monthly or more frequent incontinence in our study, indicating that parity, and perhaps labor, are risk factors, not mode of delivery. The association of vaginal delivery with incontinence was weaker in our study than in others,5,27
probably because we adjusted for multiple related factors, such as age and other medical conditions.
Urinary incontinence was an independent risk factor for fecal incontinence in this study. Other studies also have shown this association, leading investigators to believe that urinary and fecal incontinence share etiologic factors, including damage to the pelvic floor as a result of pregnancy and childbirth.10,20,28
Therefore, urinary incontinence may be a marker for pelvic floor damage and dysfunction rather than a cause of fecal incontinence. This underscores the importance of asking patients with fecal or urinary incontinence whether they experience symptoms of the other condition.
Hysterectomy, estrogen use, and menopause also were found to be independently associated with fecal incontinence. Findings on the association of hysterectomy with fecal incontinence are inconsistent in studies using multivariate analysis. Although we observed a decreased risk of fecal incontinence in females with a hysterectomy, another study found a significant increased risk of fecal incontinence after hysterectomy with oophorectomy (OR, 1.93; 95 percent CI, 1.06–3.54)10
and one study reported no association with hysterectomy.4
Females currently using estrogens were at a 30 percent increased risk of fecal incontinence. Only one study examining estrogen replacement therapy demonstrated no association in a univariate analysis.6
Recent, large, randomized trials of hormone therapy in females with urinary incontinence have found that standard doses of oral estrogen, with or without progestin, worsen urinary incontinence.29,30
A number of mechanisms for increased urinary incontinence have been suggested, including increased collagen breakdown and subsequent decreased periurethral collagen,31
and increased loose, vascular connective tissue layer of the urethra.32
Similar mechanisms may affect the rectal sphincter, resulting in fecal incontinence. When females are considering hormone therapy, they should be informed of the potential increased risk of fecal incontinence. Similarly, our finding of increased risk of fecal incontinence in postmenopausal females has not been observed in other studies, begging the inclusion of these variables in future studies of risk factors for fecal incontinence.
Finally, diabetes may contribute to fecal incontinence through neurologic and microvascular pathways. We found diabetes to be associated with a 40 percent increased risk of fecal incontinence. Previous studies also have found diabetes to increase risk for fecal incontinence.11,23
Microvascular complications associated with diabetes may damage the innervation of the rectum and pelvic floor musculature. In addition, acute hyperglycemic episodes inhibit external sphincter function and diminished rectal compliance, which can potentially exacerbate fecal incontinence.33
Several of these risk factors for fecal incontinence are potentially preventable and/or modifiable: obesity, COPD, diabetes, and irritable bowel syndrome. Management of diarrhea is a standard first line of therapy for fecal incontinence.34
Additional treatment and control of irritable bowel syndrome or diabetes and intervention for weight loss and coughing associated with COPD also may affect fecal incontinence. Identifying preventable and modifiable risk factors may guide future research for prevention or treatment of fecal incontinence. Furthermore, females with fecal incontinence should be assessed for any medical conditions that are associated with fecal incontinence because treatment of these conditions may secondarily affect symptoms of incontinence.
Our study had several limitations that should be considered when interpreting the results. First, the study is cross-sectional and thus cannot determine causal associations. Second, as in previous large epidemiologic studies, fecal incontinence was defined by self-report without specifying the consistency of stool lost or using any other characteristics that may help to define severity. Unfortunately, there are as yet no standardized definitions for severity of incontinence, which has had a significant impact on research in this field. A scoring system needs to be developed that can assign a numeric value to important variables that define incontinence, such as consistency of stool, frequency of loss, the presence of urgency, and the need for pads or diapers. A third limitation is that quality of life was measured by the SF-36, a commonly used instrument14
that is not incontinence specific, and by a question of bother. A recently validated fecal incontinence-specific quality of life instrument, the Fecal Incontinence Quality of Life instrument (FIQL), measures four areas (lifestyle, coping/behavior, depression/self-perception, and embarrassment) and is more sensitive than symptom-nonspecific scales for fecal incontinence.35
However, our study is the first to adjust the analyses of quality of life for other medical conditions that may have confounded the results. Finally, the participants in the study were generally healthy, community-dwelling volunteers who were long-term members of a large prepaid health delivery system. Before initiating the study, we determined that females who were Kaiser members since age 18 years were similar to all female members of the same age with respect to multiple characteristics, including the number of office visits in the past 27 months to gynecology, urology, and family practice/internal medicine clinics, previous hysterectomies, and use of hormone replacement therapy. However, this aspect of our study should be considered when generalizing our results to other populations.