The maintenance of urinary continence depends on intact micturition physiology (including the lower urinary tract, pelvic structures, and neurologic components), adequate pelvic floor muscle and connective tissue support, and sufficient functional ability to toilet independently. Disruption of any of these components may result in symptoms of urinary incontinence.
Risk Factors for Female Urinary Incontinence
1. Age
Both the prevalence and severity of urinary incontinence increase with advancing age.
In large population-based studies of nonpregnant women, the prevalence of urinary incontinence was approximately 3%among women younger than 35 years, 7% among those aged 55 to 64 years, and ranged from 38% to 70% among women aged 60 years and older.
Urinary incontinence is particularly common among nursing home residents, with reported prevalence rates ranging from 43% to 77%.
In addition, the type of urinary incontinence tends to change with age. Most studies suggest a shift from stress urinary incontinence (SUI) toward mixed urinary incontinence (MUI) and urgency urinary incontinence (UUI) as women age.
2. Obesity
Obesity and increased waist circumference are important risk factors for urinary incontinence. Compared with non-obese women, obese women have nearly a threefold higher risk of urinary incontinence. Chronic obesity is associated with an increased risk of developing urinary incontinence later in life.
Weight loss is associated with improvement and remission of urinary incontinence, particularly SUI. A meta-analysis of 33 studies reported that weight reduction achieved through bariatric surgery or behavioral interventions significantly reduced the prevalence of both stress and urgency urinary incontinence.
3. Pregnancy and Postpartum
The prevalence of urinary incontinence—particularly SUI—increases during pregnancy and generally rises with advancing gestational age. Overall, the prevalence of stress urinary incontinence during pregnancy is approximately 40%, and more than 50% of affected women report a significant negative impact on quality of life.
At three months postpartum, the prevalence of urinary incontinence decreases to approximately 30%, symptoms tend to be milder, and the impact on quality of life is substantially reduced. However, compared with age-matched nulliparous women, primiparous women appear to have a threefold higher risk of urinary incontinence during pregnancy and a 2.5-fold higher risk at one year postpartum.
Interestingly, the amount of weight gained during pregnancy does not appear to strongly influence the severity of urinary incontinence during pregnancy or postpartum. In contrast, postpartum weight loss may accelerate the recovery of continence. Multiple studies have demonstrated that appropriately performed pelvic floor muscle training (PFMT) has a protective effect and reduces the risk of urinary incontinence during pregnancy and postpartum, particularly when initiated immediately after delivery.
Regardless of the effectiveness of postpartum PFMT, and irrespective of whether urinary incontinence ultimately improves or resolves after childbirth, the occurrence of urinary incontinence during pregnancy is associated with a higher likelihood of developing symptomatic urinary incontinence later in life.
a. Mode of birth
Women who undergo vaginal delivery have a higher risk of urinary incontinence, particularly SUI, compared with those who deliver by cesarean section. Vaginal delivery also appears to increase the risk of UUI, although to a lesser extent than SUI. Importantly, cesarean delivery does not completely prevent urinary incontinence.
In a longitudinal study with 12 years of postpartum follow-up, cesarean delivery reduced the risk of urinary incontinence only when all deliveries were cesarean; if any delivery was vaginal, the protective effect was lost.
A history of vaginal delivery of a macrosomic infant (birth weight >4 kg) is significantly associated with an increased risk of urinary incontinence later in life. For example, among women who delivered at least one infant weighing more than 4 kg, the risk of weekly urinary incontinence was 1.47 times higher than in women without such a history.
b. Parity
Multiparity is a recognized risk factor for urinary incontinence.
A single pregnancy and delivery significantly increases the risk of urinary incontinence later in life, with an odds ratio (OR) of approximately 1.5. The risk increases further with each additional delivery. Among women with five or more deliveries, the odds ratio for developing any degree of urinary incontinence is 1.72 or higher.
The risk of urinary incontinence also appears to be related to the timing of the first delivery. Several studies suggest that women whose first delivery occurs closer to age 20 may have a higher risk, although this remains controversial. As expected, the association between parity and urinary incontinence is most pronounced for SUI.
4. Family History
Women with a family history of urinary incontinence may have a higher risk, particularly for UUI. One study found that daughters (relative risk [RR] 1.3, 95% CI 1.2–1.4) and sisters (RR 1.6, 95% CI 1.3–1.9) of women with urinary incontinence had an increased risk.
Twin studies suggest that genetic factors account for 35% to 55% of the risk for urgency urinary incontinence/overactive bladder, whereas the genetic contribution to SUI is only about 1.5%. Genetic markers have been identified for UUI, but not for SUI.
5. Race/Ethnicity
Most cross-sectional studies indicate that Caucasian women have a higher prevalence of urinary incontinence and a higher risk of incident UI and SUI compared with African-American and Asian women.
6. Hormonal Therapy
Multiple studies indicate that oral estrogen therapy, with or without progestin, is associated with the development of urinary incontinence in middle-aged and older women. In a large, well-designed randomized trial, postmenopausal women receiving placebo, estrogen alone, or estrogen plus progestin experienced nearly a twofold increase in incident urinary incontinence over one year of follow-up.
In contrast, local (vaginal) estrogen therapy has not been clearly associated with the development of SUI and has been shown to be effective for treating vaginal atrophy and recurrent urinary tract infections.
7. Smoking
Although data are somewhat inconsistent, several convincing studies have demonstrated an association between smoking and urinary incontinence. In a study of more than 2,000 Finnish women, urgency and frequency symptoms were strongly associated with current smoking status. Heavy smoking was more likely than light smoking to be associated with severe urgency symptoms.
In a cross-sectional study of over 80,000 nurses, severe urinary incontinence was associated with current smoking (OR 1.34). Among women planning surgery for SUI, the severity of urinary incontinence was significantly associated with current smoking status. Overall, recent smokers experienced 56% more episodes of urinary incontinence than nonsmokers.
8. Diet
Certain dietary factors have been associated with urinary incontinence. The strongest evidence supports an association between caffeine intake, particularly coffee consumption, and symptoms of UUI, MUI, or overactive bladder (OAB). Recent data appear to reinforce this association, especially in men.
Carbonated beverages and artificial sweeteners are primarily associated with urgency symptoms. A secondary analysis of postmenopausal women in the Women’s Health Initiative Observational Study found that consuming one or more servings of artificial sweeteners per day was associated with a 10% increased risk of mixed urinary incontinence (adjusted OR 1.10) compared with consuming less than one serving per week. No significant associations were observed for SUI or UUI, and different types of artificial sweeteners were not distinguished.
Evidence regarding alcohol consumption is very limited and suggests no significant association with urinary incontinence.
9. Medical Conditions
Urinary incontinence appears to be more common among women with certain medical conditions, particularly diabetes mellitus and depression.
The prevalence of urinary incontinence among women with type 2 diabetes may be as high as twicethat of age-matched women without diabetes. Emerging evidence suggests that women with type 1 diabetes may experience similar risks.
In a survey of more than 9,000 nurses with type 2 diabetes, 48% reported urinary incontinence at least once per month, and 29% reported weekly episodes. Obesity significantly increased the risk in this population. Similar findings were observed in an interventional trial of obese women with type 2 diabetes undergoing weight-loss treatment, in which 27%reported weekly urinary incontinence.
A cross-sectional analysis of 1,400 women with type 2 diabetes from the National Health and Nutrition Examination Survey (NHANES) identified macroalbuminuria and peripheral neuropathic pain as independent risk factors for urinary incontinence.
Data on women with type 1 diabetes are more limited. However, in a study of over 500 women with type 1 diabetes, 17%reported weekly urinary incontinence, a prevalence significantly higher than that observed in non-diabetic women in NHANES.
Depression has also been shown to be associated with urinary incontinence in women. It remains unclear whether this relationship reflects increased symptom distress among depressed women, urinary incontinence leading to depressive symptoms, or shared pathophysiologic mechanisms. Multiple studies suggest that depression increases the risk of developing urinary incontinence later in life.
10. Other Factors
A. Comorbidities and medications
Diabetes, stroke, depression, fecal incontinence, genitourinary syndrome of menopause/vaginal atrophy, hormone replacement therapy, genitourinary surgery (eg, hysterectomy), and pelvic radiation therapy have all been associated with an increased risk of urinary incontinence. However, analyses of NHANES data from 2015 to 2018 did not identify diabetes or prior hysterectomy as significant risk factors.
Other risk factors for UUI include impaired functional status, recurrent urinary tract infections, and childhood bladder symptoms, including childhood enuresis. Urinary incontinence is also common among individuals with cognitive impairment or dementia, with reported prevalence rates ranging from 10% to 38%.
B. High-impact exercise
SUI is associated with participation in high-impact physical activities, including jumping and running. In an online survey of 423 women, the prevalence of urinary incontinence was significantly higher among women participating in CrossFit training (84%) than among those attending general fitness classes (48%). In a survey of 480 competitive female weightlifters, 44% reported urinary incontinence within the previous three months.
11. Urogenital Microbiome
Emerging evidence suggests that the urogenital microbiome differs between continent and incontinent women, particularly in those with urgency urinary incontinence. However, findings regarding bacterial diversity in other types of urinary incontinence are conflicting. Additional research is needed to clarify the role of the urogenital microbiome in both health and the pathogenesis of urinary incontinence.
Contributing Factors / Conditions
● Genitourinary Syndrome of Menopause / Vaginal Atrophy
Declining estrogen levels after menopause result in thinning of the superficial and intermediate layers of the urethral mucosa. This atrophy may lead to urethritis, reduced urethral coaptation and compliance, and local irritation, all of which may contribute to urinary incontinence.
● Urinary Tract Infection
Lower urinary tract infections may present with symptoms resembling overactive bladder and exacerbate urinary incontinence. Not all women with UTIs experience dysuria or hematuria. Women with UTIs may experience worsening urinary incontinence not only during active infection but also for a period after resolution.
● Other Urologic or Gynecologic Disorders
Less common urologic or gynecologic conditions that may cause urinary incontinence include urogenital fistulas, urethral diverticula, and ectopic ureters.
● Systemic Causes
Patients with underlying medical conditions that cause urinary incontinence typically exhibit other characteristic clinical features or relevant medical histories.
a. Neurologic disorders
Spinal cord disorders may result in overflow urinary incontinence. Other neurologic conditions associated with urinary incontinence include stroke, Parkinson disease, multiple sclerosis, and normal pressure hydrocephalus.
Patients with diabetic autonomic neuropathy may develop overflow incontinence and weak urinary stream.
b. Malignancy
Less common systemic causes of urinary incontinence include bladder cancer and invasive cervical cancer.
● Potentially Reversible Causes
Potentially reversible causes or contributing factors for urinary incontinence include medications, intoxication, excessive intake of tea or caffeine, and constipation or fecal impaction.
● Functional Urinary Incontinence
Functional urinary incontinence occurs when urinary storage and voiding mechanisms are intact, but physical limitations prevent timely access to toileting. This appears to be a common contributor to urinary incontinence among older women.
In one study of 177 women aged 57 to 85 years with daily urinary incontinence, 62% reported at least one functional disability or dependence, and 24% reported specific difficulty or dependence with using the toilet. Functional urinary incontinence may be reversible when modifiable factors are addressed, such as decreased mobility after surgery, reduced manual dexterity, or medication-related sedation leading to altered cognitive or mental status.
● Cognitive Impairment
The association between cognitive impairment and urinary incontinence is partly mediated by functional limitations and disability. In addition, comorbid conditions and medications frequently contribute to the development or worsening of urinary incontinence.
References:
1.Campbell-Walsh Urology, ch74, Urinary Incontinence and Pelvic Prolapse: Epidemiology and Pathophysiology
2.https://www.uptodate.com/contents/female-urinary-incontinence-evaluation
