For a study, researchers further sought to understand the circadian regularity of urine; they looked at urinary parameters assessed by toilet uroflowmetry in hospitalized males with nocturia throughout a 24-hour period. Only in the early morning do doctors frequently encounter male patients who complain of a low maximal flow rate. However, it had not been empirically proven because most urine exams were often only done during the day for outpatients.

The 117 hospitalized male patients in this retrospective analysis had an average age of 68.7±12.8 years. A toilet-style gadget, a toilet uroflowmeter, was used on the ward to analyze the data from 4,689 urinations made by patients throughout their hospital stay. Generalized linear mixed models with an identity link function were used to analyze the records, which included voiding volume, maximum flow rate, and voiding duration, as averages of 8 time periods of 3 hours each.

After age adjustment, voiding volume was much larger at night (21:00–06:00) than it was in the morning (06:00–09:00), and it was at its maximum between 00:00–03:00. It’s interesting to note that the highest flow rate between 06:00 to 09:00 was the lowest, even after adjusting for both void volume and age. After adjusting for age and voided volume, voiding time was considerably higher at night (00:00–06:00) than during the day (06:00–09:00).

In a group of hospitalized males with nocturia, they unequivocally demonstrated the circadian cycle of urine. The maximum flow rate was the lowest early in the day, especially immediately after waking up.