Purpose: Low nocturnal urine production (NUP) may be sufficient to rule out global polyuria (GP) in men. This study determines the sensitivity of indices for nocturnal polyuria (NP), defined as nocturnal polyuria index (NPi; nocturnal urine volume/24-hour urine volume) ≥0.33 or NUP ≥90 mL/hr, for detecting GP in women.
Methods: Data were analyzed from 2 prospective protocols involving subjects recruited from a urology ambulatory care unit and a continence clinic. Women ≥18 years with nocturia were included if they met either of 2 common criteria for GP: (1) ≥40 mL/kg/24 hr or (2) ≥3,000 mL/24 hr.
Results: Thirty-one women were included (NPi, 28.6 [21.3-40.7]; NUP, 100.8 [68.3-135.8] mL/hr). At the ≥40 mL/kg/24-hr cutoff, 40% and 63% of women reporting ≥1 nocturnal void(s) (n=30) had NPi ≥0.33 and NUP ≥90 mL/hr, respectively. Additionally, 53% and 71% of subjects reporting ≥2 nocturnal voids (n=17) had NPi ≥0.33 and NUP ≥90 mL/hr, respectively. At the ≥3,000 mL/24-hr cutoff, 38% and 69% of women reporting ≥1 nocturnal void(s) (n=13) had NPi ≥0.33 and NUP ≥90 mL/hr, respectively, and 63% and 88% of subjects reporting ≥2 nocturnal voids (n=8) had NPi ≥0.33 and NUP ≥90 mL/hr, respectively. By extension, 37%-62% of women with nocturia and GP did not have NP by NPi ≥0.33 criteria, and 12%-37% did not have NP by NUP ≥90 mL/hr criteria.
Conclusion: Indices of excess nighttime urination do not reliably predict GP in women. A full-length voiding diary may be particularly important in the evaluation of women with nocturia. Nocturia in women merits further consideration as a distinct entity.
Keywords: Circadian rhythm; Nocturia; Polyuria; Sex.