Prediction of nocturnal polyuria in patients with nocturia based on voiding frequency

To examine daytime voiding patterns in patients with nocturnal polyuria (NP) and identify a novel predictive indicator based on voiding frequency ratios.

A retrospective analysis of 875 patients with nocturia from 17 Japanese institutions (January 2018-December 2022) was conducted. Patients were divided into two groups based on the nocturnal polyuria index (NPi) > 33% (NP) or ≤ 33% (non-NP). Daytime and nighttime voiding frequencies and volumes were collected from bladder diaries. The correlation between the NPi and voiding parameters was assessed using Spearman's rank correlation. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive ability of the nighttime-to-24-h voiding frequency ratio for NP.

Patients with NP urinated significantly less frequently and produced more urine during the day than those without NP (p < 0.001). The ratio of nocturnal to 24-h voiding frequency showed a significant positive correlation with NPi (r = 0.38, p < 0.001) and was the strongest predictor of NP. ROC curve analysis showed that this ratio could predict NP, with an area under the curve (AUC) of 0.79. A cutoff value of 0.23 yielded 75% sensitivity and 68% specificity for predicting NP.

This study demonstrates that patients with NP exhibit significantly reduced daytime voiding frequency and urine volume compared with those without NP. The nighttime-to-24-h voiding is useful for roughly predicting NP at the time of the initial consultation and has the potential to become more practical and accurate with further accumulation of data and research.