The purpose of this study was to determine the prevalence of fecal incontinence in a large cohort of nonpregnant, nulliparous women, and thereby construct a reference group to evaluate the effect of childbirth.

This national questionnaire survey was conducted in 2014. Statistics Sweden was requested to identify the study population from the Total Population Register. Swedish women that had not given birth and were 25 to 64 years of age were identified (n = 625 810). A sample of 20 000 was randomly selected by Statistics Sweden and invited to participate in the study by returning a postal questionnaire. The participants comprised four independent random samples, stratified by decades of age, with oversampling of the two youngest age groups for a subsequent longitudinal follow-up. The questionnaire was returned by 10 187 women. Of these 990 were excluded; 525 were parous, 194 were pregnant, 271 had an unusable returned questionnaire which resulted in a final study population of        9 197 women. Given this size of study cohorts, an alfa level of 0.05, a power value of 80%, and using Student’s t-test for the analysis, the minimum significant difference in prevalence of fecal incontinence was 2%. The women were invited to answer a 40-item questionnaire (web and postal version), which included questions about current symptoms of fecal and urinary incontinence and pelvic organ prolapse. Women were also asked about current height and weight, menstrual status, hysterectomy, menopause, and hormone treatment. Fecal incontinence was defined as the involuntary loss of feces – solid or liquid stool. Descriptive data for continuous variables were presented as numbers, mean and standard deviations (SD). Categorical data were presented as numbers and percentages and 95% confidence intervals (CI). Fisher’s exact test was used for comparisons of dichotomous variables and Student’s t-test for continuous variables when comparing two cohorts. Logistic regression analysis was used to analyze the risk of fecal incontinence between age groups. Predicted values of fecal incontinence were presented as means and 95% CI and adjusted p-values. An adjustment​ was made for age and BMI. Statistical significance was set at p < 0.05.

The response rate was 52.2%. Fecal incontinence was reported by 1 087 of 9 110 women aged 25 to 64 years (11.9%). Women with fecal incontinence were older (43.3 versus 40.4 years, p<0.0001), more often obese (BMI≥30) (21.2% versus 13.1%, p<0.0001), and postmenopausal (21.5% versus 16.6%, p<0.0001), compared to those without fecal incontinence (Table 1). 

The prevalence of fecal incontinence increased consistently with age from 9.6% among the youngest women (25 to 29.9 years) to 15.6% among the oldest (55-64.9 years), p<0.0001 (Figure 1). The rate of increase was highest during the age interval of 45-55 years and was similar for each leakage modality. Incontinence of liquid stool was almost three times more prevalent compared to incontinence of solid stool (11.1% versus 4.0% respectively). Almost every second women had incontinence of flatus (45.7%). Across ages,​ one in four women had bothersome fecal incontinence, which was rare and most prevalent among the oldest women 4.1 % versus 2.3 % among the youngest (p<0.0001). Bothersome fecal incontinence increased consistently with BMI from 2.1% among those with BMI<25 to 6.9% among women with BMI≥35 (p=0.0017).

All aspects of fecal incontinence increased with age and BMI. The prevalence of fecal incontinence increased from about 10 to 15% over a period of 40 years up to 64 years of age. Every fourth nulliparous woman had bothersome fecal incontinence.

This study has shown that nulliparous women have fecal incontinence and prevalence increases with age and BMI. This underlines the importance of using this group as a ​reference in comparisons with parous women, to estimate the effect of pregnancy, childbirth and obstetric injuries.