Urinary incontinence among women: AJOG study

The major subtypes of UI include stress, urgency, and mixed UI. The International Urogynecological Association and International Continence Society joint report defines stress UI as "observation of involuntary leakage from the urethra synchronous with effort or physical exertion, or on sneezing or coughing." Urgency UI is defined as a "complaint of involuntary loss of urine associated with urgency" and is commonly described in the context of overactive bladder (OAB) syndrome. Lastly, mixed UI is defined as "complaint of involuntary loss of urine associated with urgency and also with effort or physical exertion or on sneezing or coughing.

Rapid aging of the population in industrialized countries, the growing awareness that UI is not part of normal aging and can be remedied, and the relatively high prevalence factors that are associated with UI, such as obesity and smoking, may all influence the proportion of women recognizing and reporting UI symptoms. To address this knowledge gap, this study carried by Abufaraj M, Xu T, Cao C, et al aimed to evaluate the contemporary prevalence and trends in UI and its subtypes from 2005 to 2018 among US women and to identify sociodemographic and lifestyle correlates.

Authors used data from the National Health and Nutrition Examination Survey, a nationally representative series of surveys that was designed to evaluate the health status of the US population. Data on urinary incontinence from 7 consecutive 2-year cycles (2005-2006 to 2017-2018) were used for this study. A total of 19,791 participants aged 20 years were included. Weighted prevalence estimates and 95% confidence intervals were calculated in each study cycle for stress, urgency, and mixed urinary incontinence.

• In the 2017-2018 cycle, stress urinary incontinence was the most prevalent subtype (45.9%), followed by urgency urinary incontinence (31.1%) and mixed urinary incontinence (18.1%).

• The prevalence rates of urgency and mixed urinary incontinence were higher in women aged 60 years and older (urgency, 49.5%; mixed, 31.4%) than in those aged 40 to 59 years (urgency, 27.9% ; mixed, 15.9%) and those aged 20 to 39 years (urgency, 17.6%; mixed, 8.3%).

• The overall prevalence of stress and mixed urinary incontinence was stable throughout 2005 to 2018 (both Ptrend=0.3), with increases in mixed urinary incontinence among women aged 60 years and older (P=.001). The prevalence of urgency urinary incontinence significantly increased, particularly among women aged 60 years and older (both P=0.002).

• Age, obesity, smoking, comorbidities, and postmenopausal hormone therapy were associated with higher prevalence of all types of urinary incontinence.

• Black women were less likely to report stress urinary incontinence but more likely to report urgency urinary incontinence.

• In this representative sample of US women, stress UI was the most common type of UI, reported by at least 4 of 10 women. Urgency UI was the second most prevalent type, which was reported by approximately 3 of 10 women.

• All types of UI were more prevalent among women who were older or had a higher BMI. In addition, smoking, comorbidities, use of postmenopausal therapy, and a history of vaginal delivery made women at least 20% to 40% more likely to report stress UI, urgency UI, or both.

Vaginal delivery, by itself or through operative vaginal delivery (particularly forceps), increases the risk of stress UI, via excessive stretching of the pelvic floor muscles or possible nerve injury. A US population-based study found that the rates of forceps delivery have been decreasing, translating into less possible pelvic floor injury and resultant stress UI. Moreover, pelvic floor exercises, widely recommended nowadays by healthcare providers for women, especially after vaginal deliveries, have demonstrated remarkable efficacy in mitigating the severity of stress UI. In addition, the rates of smoking have been steadily decreasing in the United States, affecting smoking-induced cough and pelvic muscle and connective tissue injuries.

Several sociodemographic factors were found to be correlated with the prevalence and trends of UI. A non Hispanic Black race and ethnicity was significantly associated with less stress and mixed UI. African Americans have stronger pelvic floor muscles and higher urethral closure pressures than Whites.

The etiology of urgency UI is not fully understood, but it has been hypothesized to be related to an altered urinary microbiome, which may explain the observed disparities in relation to ethnicity and socioeconomic status.

A higher BMI was associated with higher prevalence of all types of UI by at least 2-folds. Obesity, as indicated by higher BMI, is associated with increased intra-abdominal pressure, precipitating stress UI. In addition, preliminary work suggests that insulin resistance, commonly associated with obesity, compromises the integrity and innervation of the pelvic floor muscles.

The association between smoking and higher prevalence of stress UI, urgency UI, or both can be construed by the effect of smoking on connective tissue quality, chronic cough, and resultant chronic diseases. Chronic diseases, such as diabetes, COPD, or cancer, can also compromise pelvic floor muscle function, increase intra-abdominal pressure, or both.

This analysis found that using estrogen and/or progesterone for postmenopausal hormone therapy was associated with at least 23% increased odds of experiencing UI of all types. The etiology is not fully understood but postmenopausal hormone therapy was found to be associated with increased bladder contractility and collagen turnover, precipitating urgency and stress UI, respectively.

"In this nationally representative survey of US women, the prevalence of stress, urgency, and mixed UI were high, affecting 45.9%, 31.1%, and 18.1% of women, respectively. Although the trends in stress UI were generally stable from 2005 to 2018, the prevalence of urgency and mixed UI significantly increased among women aged 60 years or older. Future studies are needed to address UI disparities across sociodemographic subgroups and to investigate the factors driving the rising trends in subtypes of UI among older women. In addition, focused research can help prevent and remedy this growingsocioeconomic and individually calamitous malady."

Source: Abufaraj M, Xu T, Cao C, et al. Prevalence and trends in urinary incontinence among women in the United States, 2005e2018. Am J Obstet Gynecol 2021;225:166.e1-12.

https://doi.org/10.1016/j.ajog.2021.03.016