Clinical Geriatrics

Introduction
Overactive bladder (OAB) is the syndrome of lower urinary tract symptoms (LUTS), defined by the International Continence Society (ICS) in 2002 as “urgency, with or without urge incontinence, usually with frequency and nocturia.”¹ Urgency, the sudden and compelling, often difficult (or impossible) to delay, desire to urinate is the hallmark of the OAB syndrome.² The symptom complex of OAB represents a final common pathway of dysfunctions relating to the lower urinary tract and its neurophysiologic control, concurrent systemic morbidities and pharmacology, and environmental interactions. Thus, the term overactive bladder probably should not be used as a diagnostic term, despite its widespread implication as a diagnosis in common clinical usage. Nonetheless, the use of the term among practitioners is generally understood to refer to the presence of the symptom complex in the absence of identifiable and treatable cause.

OAB is an important health problem in older women. The overall prevalence of OAB in both men and women increases with age, with notable increases in incontinence associated with OAB in women after age 40. The National Overactive BLadder Evaluation (NOBLE) program reported a prevalence of OAB in nearly one-third of women over 65 years of age, with approximately two-thirds of these women having associated incontinence.³ Patients with OAB have significant impairments in quality of life as compared with patients who have other chronic diseases. The financial costs of OAB are considerable and have been estimated to be similar to other common problems of older women, such as osteoporosis, gynecologic and breast cancers, pneumonia and influenza, and arthritis.⁴

The evaluation and treatment of OAB is aimed at discovering causes that may be corrected or compensated. While the clinical syndrome of OAB is by definition the same in older women as in other groups, the factors contributing to OAB are influenced by age and gender; thus, older women represent a unique clinical subgroup of patients with OAB.

Lower Urinary Tract Function and Dysfunction in the Older Woman
The lower urinary tract consists of two functional units: the reservoir (urinary bladder) and the outlet (urethra, bladder neck, external urethral sphincter, and striated muscles of the pelvic floor). It is innervated by an integrated afferent and efferent neuronal complex involving the parasympathetic, sympathetic, and somatic neurons, regulating the muscular activities of the bladder, urethral, and periurethral musculatures.⁵ Lower urinary tract function (storage and emptying) is ultimately a response to bladder and urethral sensory information. The micturition reflex is mediated by pathways integrating higher cortical centers with bladder afferent and efferent stimulation. During the filling phase, bladder afferents (primarily small-diameter myelinated A delta fibers) relay sensations of bladder volume to central processing centers. Functional magnetic resonance imaging (MRI) studies demonstrate complex interactions of the periaqueductal gray (PAG), thalamus, insula, dorsal anterior cingulate gyrus (ACG), orbitofrontal cortex, and pontine micturition center (PMC).⁶ Under normal circumstances, these operate with subconscious control until normal volume thresholds are reached, at which time the micturition reflex may be activated at a socially appropriate moment. Efferent signaling is relayed over parasympathetic and somatic nerves, resulting in activation of the detrusor muscle via stimulation of (primarily) M3 muscarinic receptors in the detrusor muscle, and sphincteric relaxation, resulting in normal bladder emptying.