Urinary incontinence in nulliparous women aged 25-64 years: a national survey

A systematic survey of pelvic floor disorders in nulliparous women has not been presented previously.

The purpose of this study was to determine the prevalence of urinary incontinence parameters in a large cohort of nonpregnant, nulliparous women, and thereby construct a reference group for comparisons with parous women.

This postal and World Wide Web-based questionnaire survey was conducted in 2014. The study population was identified from the Total Population Register in Sweden and comprised women who had not given birth and were aged 25-64 years. Four independent age-stratified, random samples comprising 20,000 women were obtained from the total number of eligible nullipara (n = 625,810). A 40-item questionnaire about pelvic floor symptoms, its severity, and its consequences were used. Age-dependent differences for various aspects of urinary incontinence were analyzed with the youngest group (25-34 years) serving as reference. Crude and body mass index-adjusted prevalence and its 95% confidence limits were calculated for each 10-year category.

The response rate was 52% and the number of study participants was 9197. Urinary incontinence increased >5-fold from 9.7% in the youngest women with a body mass index <25 kg/m² to 48.4% among the oldest women with a body mass index ≥35 kg/m². The prevalence of bothersome urinary incontinence almost tripled from 2.8-7.9% among all nulliparas. The proportion with bothersome urinary incontinence among incontinent women increased from 24.4% in the youngest age group to 32.3% in the age group 55-64 years. Nocturia ≥2/night increased 4-fold to 17.0% and leakage ≥1/wk increased 3-fold to 12.8% among the oldest women. Mixed urinary incontinence increased from 22.9-40.9% among the oldest 0-para with incontinence, whereas stress urinary incontinence decreased inversely from 43.6-33.0%. In the total cohort surgical treatment for urinary incontinence occurred in 3 per thousand.

Almost every aspect of urinary incontinence was present in nulliparous women of all ages and prevalence increased with advancing age between 25-64 years. This must be taken into account when using nullipara as a control group in comparisons with parous women to estimate the effect of pregnancy and childbirth.