Overactive bladder (OAB) syndrome is the urgent, sudden and compelling desire to void which is difficult to delay. Several reasons are thought to account for the development of OAB: morphologic changes of the detrusor muscle of the bladder (e.g., patchy denervation of detrusor muscle bundles), neurologic changes (e.g., ischaemic nerve damage), age-related causes of urinary dysfunction, and metabolic causes (e.g., disturbed serotonin metabolism). The prevalence of OAB in Europe is reported to be 4.6% to 15.0 % in men and 14.0% to 40.0% in women.
In contrast, nocturia is the awakening from sleep to urinate. This is a common symptom in a variety of medical disorders and in the elderly. Awakening from sleep as a result of nocturia is thought to be secondary to a sensation of urinary urgency resulting from an overextended bladder.
Studies have reported that 10% of the general population over age 20 has nocturia two or more times per night. In the 50-59 age group, 58% of men and 66% of women experience nocturia. In those over age 80, 72% of men and 91% of women report nocturia. Nocturia-related awakenings can also cause significant sleep disruption and fatigue in elderly patients and are correlated with an increased number of falls at night.
Older men who have nocturia are often assumed to have benign prostatic hypertrophy and older women with nocturia are often assumed to have an unstable bladder or reduced bladder capacity associated with aging. However, nocturia occurs as a result of overproduction of urine, rather than diminished bladder capacity or prostatic hypertrophy.
New medical evidence confirms that obstructive sleep apnoea (OSA) is associated with a high incidence of both nocturia and overactive bladder syndrome. Based upon study findings a model has been developed to illustrate the complex set of events surrounding OSA leading to polyuria (excess urine production).
The overall impact of OSA is not just sleep deprivation; it is also a repetitive noxious cardiovascular event. In addition, OSA natriuresis is now identified as a mechanism for nocturnal polyuria (nocturia, enuresis and incontinence).
Recent studies demonstrate that nocturia was an independent predictor for severe obstructive sleep apnea (OSA), and therefore a marker of greater risk of stroke recurrence and mortality after stroke. Since nocturia is common in post-stroke patients with OSA, this recent study explored the predictive role of nocturia for severe OSA in patients with ischaemic stroke. Sixty-five patients with ischemic stroke admitted to rehabilitation ward received polysomnography and clinical assessments, including a 3-day urinary frequency–volume recording.
Patients with severe OSA were older (69.6 ± 9.9 vs. 62.6 ± 11.5 year), had a significantly higher oxygen desaturation index (37.9 ± 16.1 vs. 8.8 ± 6.1 episodes/night) and had a higher frequency of nocturia (2.2 ± 1.0 vs. 1.5 ± 0.8 episodes/night) than those without. In addition, men with severe OSA had a larger neck circumference (409 ± 26 vs. 381 ± 32 mm) than those without. The frequency of nocturia, age, sex, and interaction between sex and neck circumference remained significant in the final model for severe OSA.
The odds ratio of nocturia was highest (3.5) among the four variables consistent with nocturia being an independent predictor for severe OSA. For this reason increasing evidence favours all patients with ischemic stroke being screened for severe OSA.