Nocturnal Polyuria in Older Adults: Pathophysiology and Diagnostic Approaches

Abstract

Introduction: Nocturnal polyuria (NP), defined as overproduction of urine at night, is a leading cause of nocturia. Its pathophysiology in aging remains incompletely understood. This review synthesizes current evidence on NP mechanisms and diagnostic strategies.

Methods: A literature review was performed in MEDLINE and CINAHL (2015–2023) for studies on adults ≥60 years with NP (nocturnal urine production >20% of 24-hour volume). We extracted data on circadian arginine vasopressin (AVP) secretion, renal function, and diagnostic tests.

Results: Twenty-three studies (n=4,201) showed that 58% of older adults with nocturia meet NP criteria. Blunted nocturnal AVP surge was found in 67% of NP patients. Reduced glomerular filtration rate nocturnally did not explain polyuria. The 24-hour frequency-volume chart (FVC) had 89% sensitivity for diagnosis. Morning-to-evening osmolality ratio <1.2 was a simple screening tool (AUC 0.82).

Discussion: Age-related loss of circadian AVP rhythm appears central to NP, not simply renal water handling defects. Many studies excluded men with BPH, potentially underestimating mixed pathology. Standardized NP definitions across societies are still lacking.

Conclusions: Nocturnal polyuria in older adults is primarily a neuroendocrine circadian disorder. Diagnosis requires FVC or validated questionnaires. Desmopressin trials show efficacy, but hyponatremia risk mandates cautious use.