EpidemiologyUrinary incontinence is defined as involuntary loss of urine. The prevalence of UI increases with age. Moderate to severe UI affects 7% of women 20 to 39 yrs of age, 17% of 40 to 59 yrs of age, 23%of 60 to 79 yrs of age , and 32% of ≥80 yrs of age [1] . With global population aging, the absolute numbers of older persons with UI are increasing exponentially. The primary impact of UI is on quality of life, including self-concept, self-esteem, and the burden of coping. Economic costs of UI continue to rise, adding an estimated $26 billion annually to the cost of caring the elderly in USA [2] .
AetiologyWhereas UI in younger and middle-aged persons is nearly entirely caused by alteration in the lower urinary tract (LUT) and its innervation, in older persons, UI represents a geriatric syndrome with broadly based, patient level risk factors that include age-related changes in physiology, comorbidity, medications, and especially functional impairments [3,4] . Moreover, in older persons, UI can cause significant morbidity (such as falls and fractures) and functional impairment. Additionally, many older and especially frailer persons require caregivers, and UI can lead to caregiver stress and institutionalization of the frail elder. Risk factors for UI in older persons include impaired mobility, falls, medications, depression, transient ischemic attacks and stroke, dementia, congestive heart failure, fecal incontinence and constipation, and obesity [4] .
Age-related Changes in the Lower Urinary TractDetrusor contraction strength declines with age in women as well as men, and there is no detrusor overactivity (DO) associated increase in contractility [5] . Lack of estrogen contributes to, and estrogen replacement reverses, ultrastructural changes of impaired contractility (caveolar depletion and detrusor fibrosis), while low estrogen also may contribute to bladder muscle cell differentiation [6] . In the urethra, closure pressure decreases by an estimated 15 cm H 2 O per decade [7] , possibly related to mucosal changes extending to the bladder trigone, irritating sensory afferent nerves and triggering DO, and decreased urethral vascular density and blood flow (note: these studies did not control for vascular risk factors) [8,9] . Circular smooth muscle mass and fiber counts decrease, with striated muscle loss in the anterior urethra [10] . Little remains known about urethral changes in older men other than prostatic obstruction. Despite evidence for levator denervation and decreased muscle fiber number, type, and diameter, pelvic floor dysfunction whether defined as stress UI (SUI), resting and volitional vaginal closure force, or pelvic organ prolapse is not associated with age after controlling for obesity, parity, menopause, and hormone use [11] . The vagina shortens by a clinically insignificant 0.08 cm per 10 years [12] . Post-menopausal atrophy may cause loss of lactobacillus and colonization with pathogenic organisms (E. coli, enterococci, etc), leading to higher rates of bacteriuria and symptomatic uri...