Analysis of changes in the pathophysiology of nocturia according to the number of nocturia episode, age, and gender using frequency volume charts: A retrospective observational study

Purpose: To evaluate the pathophysiology of nocturia based on the frequency volume chart, and determine the risk factors for nocturia occurring >= 2 times per night. Materials and methods: In this retrospective study, we reviewed 311 patients with complaints of nocturia from January 2017 to February 2019 at our institution. Nocturnal polyuria (NP) and global polyuria (GP) were defined as NP index >0.35 regardless of age and 24 h urine volume >2.5 L/day, respectively. Decreased bladder capacity (dBC) was when the maximal voided volume was <325 mL. Decreased nocturnal bladder capacity (dNBC) was defined as nocturnal bladder capacity index >0. Results: In total, 273 patients were included in the primary analyses. Of 802 days from 273 frequency volume charts, the median number of nocturia was 1 episode per day. Further, NP (odds ratios [OR] 7.01), GP (OR 4.25), dBC (OR 3.00), dNBC (OR 10.12), and age (OR 1.04) had the association with nocturia >= 2 times per night. There was a significant stepwise increase in NP, dNBC, dBC, and GP with the number of nocturia episodes. As patient age increased, the likelihood of NP (P < 0.001) and dBC (P < 0.001) being the cause for nocturia tended to increase, but that of dNBC (P = 0.022) and nocturia without cause (P = 0.007) tended to decrease. Moreover, dBC was more likely to cause nocturia in female patients than in male patients (P < 0.001). Conclusion: NP, dBC, dNBC, and GP are important factors involved in the pathophysiology of nocturia occurring >= 2 times per night.