Determinants of nocturia severity in men, derived from frequency-volume charts

Objective. Nocturia may be characterized by indices derived from the frequency-volume chart (FVC). The objective of this study was to determine how these parameters relate to the severity of nocturia in men with and without lower urinary tract symptoms (LUTS). Materials and methods. A retrospective analysis of FVCs was performed in two cohorts of men: those presenting with LUTS in a New York ambulatory urology clinic and those from the longitudinal population-based Krimpen study. Nocturnal urine volume (NUV), nocturia index (Ni), nocturnal polyuria index (NPi), nocturnal maximal voided volume (nMVV) and sleep duration were derived from FVCs. Comparisons were made using Spearman's rank correlation coefficient between actual number of nightly voids (ANV) and the other diary parameters. Results. Eighty-eight consecutive men who presented with LUTS completed a 24 h FVC [median age 70 years, interquartile range (IQR) 64.5-74.5, median ANV 2, IQR 1.5-4]. Nocturnal voiding frequency and volume were analyzed in 1082 community-dwelling men (median age 61 years, IQR 56.1-66.4, range 49.4-78.2; median ANV 1.5, IQR 1.0-2.0, range 0-4.5). Both cohorts demonstrated strong correlations between nocturia severity (represented as ANV) and Ni (0.797, 0.658 for cohorts 1 and 2, respectively). There were moderate correlations between nocturia severity and NPi (0.545, 0.394), NUV (0.463, 0.432) and sleep duration (0.306, 0.272). The nMVV correlated poorly with nocturia severity (0.159, 0.146). Conclusions. Treatment of nocturia should aim to match nocturnal urine production with bladder capacity. Given the lack of known effective pharmacotherapy for low bladder volume, the first attempt nocturia treatment could focus on volume reduction.