Exploring nocturia: Gender, age, and causes

PURPOSE: This study aims to clarify differences in parameters based on frequency volume chart (FVC) and on daytime and nighttime urine according to the nocturia frequency, age, and gender. MATERIALS AND METHODS: This observational study was executed between 2011 and 2013. Participants (>18 years, ≤65 years) with or without nocturia (controls) were included and completed a 72 hr FVC; osmolality and sodium excretion were analyzed on daytime and nighttime urine. RESULTS: (1) Nocturia severity: Compared to controls (N = 38), those with ≥2 nocturia episodes (N = 29) have higher nocturnal voided volume (NVV) (P < 0.001) based on increased sodium excretion (P = 0.003) and lower functional bladder capacity (P < 0.001). Those with one nocturia episode (N = 21) present with lower bladder capacity (P = 0.005). (2) Gender: women with 1 and ≥2 episodes have lower bladder capacity than controls (P = 0.047 and P < 0.001, respectively). Men with ≥2 episodes present with increased NVV (P = 0.001) and decreased bladder capacity (P = 0.049). (3) Age: Younger participants (<44 years) with ≥2 nocturia episodes present with lower functional bladder capacity than controls (P < 0.001). Older participants (45-65 years) present with both increasing NVV and decreasing bladder capacity with increasing nocturia frequency (P < 0.001); sodium excretion is higher in those with ≥2 episodes (P = 0.029). (4) Causes: the percentage of isolated NP decreases (P = 0.005), whereas the combination of both causes increases with increase in number of nocturia episodes (P = 0.020). CONCLUSIONS: The mismatch between functional bladder capacity and NVV with increasing nocturia frequency demands a comprehensive diagnostic approach to subtype the patient, which involves anamnesis, FVC, and analysis of daytime and nighttime urine.