Subtypes of overactive bladder in old age

Age and Ageing,  March, 1993  by Gudmundur Geirsson,  Magnus Fall,  Sivert Lindstrom

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Introduction

Urinary incontinence is widespread, includes a range of types and severity and increases with age. According to community-based surveys, the prevalence of urinary incontinence is roughly 8% in the active adult population |1-3~. The validity and reliability of such selected samples have been debated but the general figure quoted has been confirmed in a large nation-wide study in Sweden |4~. In the elderly population, the prevalence increases dramatically, the condition being reported in as many as 40% or more of subjects above 85 years of age |5-7~. The dominating symptom in old age, in both sexes, is urge incontinence, mainly related to bladder overactivity. In patients over 70, detrusor overactivity was found in 50% of the men and more than 30% of the women |8~. Resnick et al. |6~ identified bladder overactivity as the predominant cause of incontinence in 61% of institutionalized elderly persons (mean age 89 years).

It is well known that discrete or diffuse degenerative changes within the central nervous system increase with age, as do better defined clinical conditions such as dementia, cerebral vascular insults and Parkinson's disease. Such observations are in general agreement with our hypothesis that bladder overactivity primarily results from a disturbed central neuronal control of the lower urinary tract |9~. If this is true, different functional patterns are to be expected depending on the site and extent of the neuronal dysfunction. In line with this reasoning, we have recently proposed a new functional subdivision of overactive bladders based on cystometry and clinical findings |9,10~. Three main categories with different symptom patterns have been identified, namely uninhibited overactive bladder (UOB), characterized by impaired perception of bladder fullness and loss of voluntary inhibition of micturition contractions, phasic detrusor instability (PDI), with spontaneous or provoked abortive detrusor contractions during the bladder filling phase, and spinal detrusor hyperreflexia (SDH), following spinal upper motor neuron lesions with impaired voluntary command and unco-ordinated micturition reflexes. We have now studied the distribution of these three subtypes of overactive bladders in a large group of patients, aged over 65 years.

Patients and Methods

All subjects with overactive bladders were selected from the list of patients examined at our urodynamic laboratory during the three-year period 1986-8 (n=1794). Patients with urinary tract infection, possible infravesical outflow obstruction and indwelling catheters were excluded. Almost all patients were ambulatory, and the majority, except those with complete upper motor neuron lesion, had symptoms of urge with or without incontinence.

All patients underwent water-fill cystometry assessed by standards recommended by the ICS |11~. In addition, a two-minute inhibition test and an ice-water test |9, 12~ were performed. Simultaneous urethral pressure measurements or sphincter EMG recordings were not systematically performed. Preserved neuronal control of the sphincter was assessed by recording absence of leakage from the urethra at concomitant voluntary inhibition of the detrusor or during the ongoing detrusor contraction while the patient was instructed to inhibit micturition. Thus, the inhibition test measures two separate functions: the ability to inhibit the detrusor and to control the external sphincter.

Each patient was, if possible, referred to one of the defined urodynamic subtypes as described below. The outcome of the urodynamic investigation was also correlated with the occurrence of clinical neuropathy obtained from medical records.

Our subdivision of overactive bladder has been described in detail elsewhere |9, 10~. The uninhibited overactive bladder (UOB) (Figure IA) is characterized by impaired perception of bladder fullness and loss of voluntary inhibition of micturition contraction. During cystometry, the first desire to void is experienced at normal or subnormal volume and is almost immediately followed by an involuntary micturition. The patient does not experience a strong desire to void until he is already voiding with a sustained detrusor contraction and a concomitant relaxation of the urethra, i.e. a coordinated micturition. At this stage, the patient is typically unable to interrupt the micturition voluntarily (inhibition test). The ice-water test is usually positive. Patients were referred to this category if they had the typical perception defect and could not voluntarily inhibit a sustained detrusor contraction.

Phasic detrusor instability (PDI) (Figure 1B), is characterized by urgency of micturition and/or urge incontinence, normal or increased bladder sensation and phasic bladder contractions occurring spontaneously during bladder filling or being provoked by rapid filling, coughing, jumping or other external mechanical stimuli. Voiding is co-ordinated and can in most cases be voluntarily delayed during a two-minute cystometric inhibition test. Typically, the ice-water test is negative. Patients were referred to this group if they presented phasic detrusor contractions (above 15 cm |H.sub.2~O) and had normal perception of bladder fullness.