In this cohort of middle-aged and older women, almost two-thirds reported obstructive defecation at least once in the past year. Symptoms that occurred weekly or more often was reported by 12% of the cohort, which is consistent with, albeit at the lower end of, the overall prevalence of constipation reported in other population-based studies of women [1
]. In this study, we asked women to define their constipation symptoms based primarily on symptoms of obstructive defecation, which is known to be more common than infrequent stools in women [4
]. This assessment strategy may have resulted in a lower estimated prevalence of constipation in our cohort than in other studies that used a broader definition. However, since constipation is known to be characterized by a range of symptoms, further investigation is needed about which characteristics contribute most prominently to a person’s perception of their constipation.
We identified several risk factors that were independently associated with obstructive defecation occurring at least weekly. These included employment status, symptoms of pelvic organ prolapse, gynecologic or pelvic surgery, use of three or more medications, and IBS. Women who were unemployed had a more than two times greater odds of reporting obstructive defecation. The importance of this finding is unclear, although it is possible that a lower socioeconomic status may affect diet, physical activity and other lifestyle factors that are known to affect constipation [15
In our population-based study, women with symptomatic pelvic organ prolapse were two times more likely to report symptoms of obstructive defecation. Prior studies of concurrent constipation and pelvic organ prolapse in specialty clinic (urogynecology or gastroenterology) populations have produced contradictory conclusions. A fourfold increased odds of constipation was noted in one study of women with pelvic organ prolapse [23
], while other studies have shown no association between pelvic organ prolapse and constipation [16
]. Clearly, more longitudinal studies are required to assess the causal relationship of these two conditions. It is unclear whether chronic constipation and straining predispose patients to develop pelvic organ prolapse, or if the presence of pelvic organ prolapse exacerbates obstructive defecation by causing rectal outlet obstruction due to rectoceles, rectal prolapse and intussusception, or even pelvic floor dyssynergia.
The effect of hysterectomy on constipation has also been examined, with variable results. One prospective study found no increase in constipation symptoms after abdominal or vaginal hysterectomies for benign conditions [25
], and another cross-sectional study of hysterectomy and painless constipation found no significant association [26
]. However, a fourfold increased odds of obstructive defecation was noted in patients recruited from a gastroenterology clinic who had a history of hysterectomy. [16
]. Our study found that the odds of obstructive defecation increased twofold when women had a history of vaginal or laparoscopic hysterectomy, whereas abdominal hysterectomy did not confer any additional risk. This finding is noteworthy in that bowel habits have not been investigated in studies comparing abdominal, vaginal and laparoscopic hysterectomy approaches [27
]. Additional studies of changes in bowel function after vaginal and laparoscopic hysterectomy are needed to assess their individual contributions to constipation. In a similar vein, we demonstrated an increased odds of obstructive defecation in women who had undergone surgery for urinary incontinence or other pelvic surgery that did not include hysterectomy. There are no existing data about the causal effect of this type of surgery on constipation, but an increased odds of chronic constipation has been demonstrated in women with mixed and stress urinary incontinence [29
Our study also demonstrated the independent association of irritable bowel syndrome with obstructive defecation. IBS is characterized by constipation, diarrhea or alternating bowel habits. Similarly, we confirmed an independent association of fecal incontinence and IBS in a previous study [30
]. However, the risk of constipation with increasing number of medications has not been reliably demonstrated in other studies. In an investigation of over 60,000 women in the Nurses’ Health Study who were asked about their bowel habits, constipation was defined as having less than two bowel movements per week. The authors reported that the number of medications used was not significantly associated with constipation. However, in a separate study of risk factors in 14,000 patients diagnosed with constipation compared with 7,000 controls, a more detailed analysis of medications, based on class of drugs, demonstrated an increased risk of constipation with the use of opioids, diuretics, antidepressants, antihistamines, antispasmodics, anticonvulsants and aluminum antacids [17
]. Because many constipated patients may be using medication to ameliorate their condition, examining specific types of medications, as opposed to the number, may be more useful in understanding the relationship between constipation and medication usage.
Although reported as risk factors in other studies [15
], age and increased weight were not significant in our cohort of women. Our racially diverse population also provided a unique opportunity for us to examine racial differences in constipation, which has not previously been examined. However, we did not find any significant associations of race and obstructive defecation.
Obstructive defecation was also independently associated with a diminished general quality of life as measured by the SF-36, with a greater impact on mental health than on physical health. The importance of assessing constipation-related quality of life has become increasingly evident, especially when specific criteria that define constipation do not reflect the perceptions of those being evaluated. Few studies have actually examined the effect of constipation on quality of life. Two studies using the Rome criteria to identify functional constipation also found a significant decrease in the physical and mental component scores of patients with constipation compared to those without symptoms [18
]. However, our study is the first to adjust the analyses of quality of life for other medical conditions that may have confounded the results. This may explain why the effect of obstructive defecation on the physical component score was not significant after adjustment for these variables. However, the use of adjusted quality of life scores provides a more accurate representation of the specific effect of obstructive defecation on quality of life, which is similar to what a constipation-related quality of life measure would accomplish.
Our study had several limitations that should be considered when one is interpreting the results. First, this was a cross-sectional study that could not determine the incidence of obstructive defecation or causal associations. Second, as in previous large epidemiological studies, obstructive defecation was defined by self-report without using consensus criteria for functional constipation, obstructive defecation or irritable bowel syndrome, or specifying many of the characteristics that might have helped to define severity. As this study was designed to examine risk factors for urinary incontinence, questions about bowel habits and associated symptoms of constipation were limited and thus made it difficult to define subtypes of constipation. However, at the time of this study, no widely used, validated and reliable instrument was available to evaluate the severity of constipation. Lack of such an instrument has had a significant impact on research in this field. Consensus criteria, such as the Rome II, which are commonly used to assess constipation, can identify subtypes of constipation but do not determine severity of symptoms [32
]. In addition, the Rome criteria do not capture all people who consider themselves constipated by self-report measures [5
]. Quality of life has been measured by the SF-36, a commonly used instrument [34
] that is not specific to constipation. Only recently has a constipation-specific quality of life measure been developed [35
]. Finally, our cohort was made up of generally healthy, community-dwelling women who had been Kaiser members since age 18 years. They were found to be similar to all women members of the same age with respect to several characteristics, including the number of office visits in the past 27 months to gynecology, urology, and family practice/internal medicine clinics, prior hysterectomies and use of hormone replacement therapy. However, other potential differences in our cohort should be considered when one is generalizing our results to other populations.
In summary, obstructive defecation is a common problem in women that has a significant impact on overall quality of life. Women are at increased risk for this condition as they are more likely to have IBS, pelvic organ prolapse, and pelvic surgery. Health care providers should be aware that the anterior and posterior compartments of the pelvis might have a more integrated relationship than previously noted and, thus, should conduct a more comprehensive evaluation in patients presenting with urinary or vaginal complaints.