Classification of nocturia in the adult and elderly patient: a review of clinical criteria and selected literature.

Nocturia increases with age and significantly affects quality of life in both men and women. Attempts to determine the pathogenesis of nocturia have been based on frequency-volume charts, and three types of nocturia have been identified: low voided volume (previously termed low bladder capacity), nocturnal polyuria, and mixed origin. Validated clinical criteria based on frequency-volume data allow the type of nocturia to be specified using two threshold values, i.e. largest voided volume/body weight ratio <4 mL/kg for low voided volume; and nocturnal urinary output/body weight ratio >10 mL/kg for nocturnal polyuria. The utility of these thresholds was validated in a study of elderly patients with two or more nocturia episodes/night. Two other studies have improved the understanding of the epidemiology of nocturia. The first showed that in men and women, increased incidence with age was greater for nocturia than for the six other common lower urinary tract symptoms. The second study suggested that prostate changes in men (particularly bladder outlet obstruction caused by benign prostatic hyperplasia, which has been considered to be a major cause of nocturia) appear to play a relatively small role in the development of nocturia; the correlation was based on overall symptom score for seven common urological symptoms. Nocturia should thus be treated independently of other lower urinary tract symptoms, especially in men. The application of valid diagnostic criteria to differentiate the underlying cause of nocturia should help lead to more appropriate and effective management of this pervasive problem.