Chronobiology of micturition: putative role of the circadian clock

Purpose: Mammals urinate less frequently during sleep period than during awake period, which is modulated by triad factors; decreased arousal level in the brain, decreased urine production rate from the kidneys, and increased functional bladder capacity during sleep. The circadian clock (‘the clock’) is genetic transcription-translation feedback machinery. The clock exists in most organs and cells, termed ‘peripheral clock’, which is orchestrated by the central clock in the suprachiasmatic nucleus of the brain. In this review we discuss the linkage between the day-and-night change in micturition frequency and the genetic rhythm maintained by the clock system, focusing on brain, kidney and bladder. Material and Methods: We performed inclusive review of the literature on diurnal change in micturition frequency, urine volume, functional bladder capacity and urodynamics in humans and rodents, and related it with recent basic biological findings about the circadian clock. Results: In humans, various behavioral studies demonstrated diurna