A longitudinal study of urinary incontinence in community-based women: prevalence, incidence, resolution, and associated factors, and impact on well-being and quality of life

Background Available data indicate that urinary incontinence (UI) is a condition in women, which adversely impacts on quality of life and daily activities. It affects women of all ages, but is particularly common in older women. It has been associated with significant physical morbidities, lowered well-being, loss of independence as well as sexual difficulties. It also causes a considerable financial burden on both individuals and the healthcare system. A detailed understanding of UI in terms of its prevalence, incidence and risk factors in women is an essential step in reducing the impact of this condition. However, the reported prevalence of UI among women varies widely between studies, with most studies reporting a prevalence of any UI in the range of 25 to 50%. This range is a result of the different definitions used for UI, the heterogeneity of study populations and the different data collection procedures applied for this sensitive health issue. UI is commonly viewed as a permanent condition once it develops. However, few studies have examined the progression and resolution of UI in community-based women with or without treatment. To date no study of the prevalence and incidence of UI in Australian women has been undertaken using a validated instrument. Also, little is known about the natural history of UI and its association with fecal incontinence. The aetiology of UI is widely recognised to be multifactorial and various risk factors have been identified in different studies. However, the estimated magnitude of risks varies widely in these studies and there is inconsistent evidence with regard to certain factors including mode of delivery, hysterectomy and hormone therapy use. Aims The aims of this doctoral thesis are to comprehensively examine UI in community-dwelling women in Australia in terms of its age-specific prevalence, risk factors, impact on quality of life, natural history (incidence and resolution) and its relationship with fecal incontinence (FI). Methods The project involved 542 community-based women aged 24 to 80 years in 2006 who were originally recruited from a previous cross-sectional study of 1423 women who participated in the Study of Androgens in Women (SAW). The SAW women were recruited from a database established from the Victorian Electoral Roll. Of the 1423 women who participated in the SAW, 754 agreed to be re-contacted regarding further research and of those, 542 women expressed interest in participating in the study of UI. A detailed self-administered questionnaire was mailed to the participants of this research at baseline in 2006 and again at follow-up in 2008. UI was assessed using a validated questionnaire, the Questionnaire for Urinary Incontinence Diagnosis (QUID) and FI by the Pelvic Floor Distress Inventory (PFDI). The PFDI was included in the follow-up study only. Definitions of stress and urge UI that conform to the standards recommended by the International Continence Society were used. The Bristol Female Lower Urinary Tract Symptoms Questionnaire (BFLUTS) was used to assess the impact of UI on condition-specific quality of life. The impact of UI on well-being was assessed using the Psychological General Well-being Index (PGWBI). Results Five hundred and six women provided data for the baseline analysis and 442 women for the follow-up data analysis. Prevalence: The overall point prevalence of any UI was 41.7% [95% confidence interval (CI): 37.2-45.8%] at baseline and increased to 44.6% [95%CI: 40.0-49.2%] by the end of the follow-up period. Of the 210 women reporting UI at baseline, 16% [95%CI: 12.9-19.3%] reported stress UI; 7.5% [95%CI: 5.2-9.8%] reported urge UI and 18% [95%CI: 14.7-21.5%] reported a mixed pattern. Stress UI was found to be the most common type among middle-aged women (25.3% of women aged 35-44 years), while urge UI was the most common type in women over the age of 75 years (24.2%). Risk factors: In logistic regression analyses, obesity (P<0.001) and parity (P=0.019) were found to be associated significantly with stress UI. Greater age (P=0.002) was associated significantly with urge UI, and higher body mass index (BMI) (P=0.035) and hysterectomy (P=0.021) were associated significantly with mixed UI. Impact on well-being and quality of life: Incontinent women had a lower total PGWBI score (76.9 ± 16.5), indicating lower well-being than women with no UI (81.6 ± 15.3) (p=0.001). The total PGWBI mean score was significantly lower in women suffering from stress UI (77.8 ± 16.2, p=0.05) and mixed UI (74.2 ± 17.8, p<0.001) compared with women with no UI. All types of UI were associated with impaired quality of life (p<0.001) and adversely impacted on daily activities, as determined by BFLUTS. Change over time: Over the 2-year follow-up period the incidence of any UI was 17% [95%CI: 12.4-21.6%] among the unaffected women and the resolution was 16.8 % [95%CI: 11.4-22.2%] among the incontinent women including women who had no treatment for UI. There was also movement of women between diagnoses of stress UI, urge UI and mixed type during the follow-up period. Only 34 women reported specific treatment for their UI during the follow-up period, and of them, 5 experienced resolution of their condition. Relationship with FI: The overall prevalence of any FI at follow-up was 20.7% (95% CI: 16.9%–24.5%). The prevalence for loose FI was 20.7% (95% CI: 16.9%–24.5%) and well-formed FI, 4.5% (95% CI: 2.6%–6.4%). All of the women with well-formed FI also reported loose FI. About two-thirds of the women with any FI reported co-existing UI. Loose FI was associated significantly with any UI [OR, 2.8(95% CI: 1.7-4.8)] after adjusting for age and BMI (p<0.001). Conclusions Stress, urge and mixed incontinence have different age distributions and risk factors. Stress UI is the most common type in women at midlife and urge UI at older ages. UI is a dynamic clinical condition, with movement between diagnostic subtypes of stress, urge and mixed UI and periods of resolution. Having any UI negatively impacts on well-being and is significantly associated with impaired quality of life. The relatively low proportion of women who have treatment for their UI suggests there are barriers to treatment that merit further investigation. Loose FI is also a common condition, affecting one in five adult women in our study. Women with loose FI were more likely to have UI, independent of their age and BMI. It is therefore important that clinicians are aware that this is not an uncommon problem and consider the possibility of FI when assessing patients, especially women with UI.