Patients with nocturia due to nocturnal polyuria syndrome (NPS) have unique circadian changes in diuresis that may be amenable to treatment, according to researchers.

To characterize NPS, Thomas F. Monaghan, MD, of SUNY Downstate Medical Center in New York, and colleagues examined circadian variation in diuresis in 130 male veterans with and without NPS using 24-hour frequency-volume charts. To minimize confounding, the investigators excluded patients on diuretics or with sleep apnea, heart failure, edema, kidney disease, or diabetes insipidus.

The team used 2 different definitions of NPS for analyses: nocturnal urine production exceeding 90 mL per hour or a nocturnal polyuria index (NPi) greater than 33%.

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Early and late nocturnal diuresis rates differed significantly for patients with but not without NPS, according to results published in European Urology Focus. The group of NPS patients with nocturnal urine production exceeding 90 mL per hour had a significantly higher early vs late nocturnal diuresis rate: 152 vs 120 mL per hour. The group of NPS patients meeting the NPi cutoff likewise had a higher early rate: 120 vs 91 mL per hour.

Men without NPS showed uniform early vs late nocturnal diuresis rates by either definition (nocturnal urine production less than 90 mL per hour: 60 vs 59 mL per hour; NPi less than 33%: 75 vs 75 mL per hour).

The investigators defined early nocturnal diuresis as the first nocturnal voided volume within the first uninterrupted sleep period. Late nocturnal diuresis was the remaining nocturnal urine volume voided during the remaining hours of sleep.

“There exists a significant drop-off in nocturnal diuresis rate after the time of first awakening that is unique to patients with NPS,” Dr Monaghan’s team explained. “Our finding that these individuals produce urine at the highest rate in the early hours of sleep suggests that they may benefit from pharmaceuticals specifically designed to reduce urine production during this period.”

Among the study’s limitations, the team could not fully account for fluid intake, nor could they exclude the possible influence of non-dipping hypertension.

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Monaghan TF, Suss NR, Epstein MR, et al. Differential Nocturnal Diuresis Rates Among Patients With and Without Nocturnal Polyuria Syndrome. Eur Urol Focus. DOI:10.1016/j.euf.2018.10.015