Nocturia and complementary indices: determination and quantification of the cause of nocturia by frequency-volume charts in women with lower urinary tract symptoms

We evaluated differences between women with lower urinary tract symptoms (LUTS) with and without nocturia in terms of voiding habits, urine production and voided volumes in order to determine and quantify the cause of nocturia by using frequency-volume (FV) charts. At the initial visit, all patients underwent a detailed clinical evaluation including an International Prostate Symptom Score assessment, received a thorough explanation from the study coordinators, and were requested to complete a 3-day FV chart. Of the 123 women enrolled, 106 (86.2%) 20–83 years old (median age 55.0) completed the study. Nocturnal urine volume was higher in nocturics than in non-nocturics, but this was not statistically significant. Total daytime voided volume was lower in nocturics than in non-nocturics (P=0.030) but with no detectable difference in total voided volume. To identify possible risk factors, we examined age and night time parameters including the nocturnal bladder capacity index (NBCI), nocturnal polyuria index (NPI) and nocturia index (NI) by univariate logistic analysis. When nocturia was defined as voiding at least twice per night, age and NI were found to be associated with it by univariate analysis. These two variables were further analyzed using a multivariate logistic model to determine their association with nocturia. In the multivariate analysis, a positive association was observed between age and nocturia. Patients 50 years or older had a 3.9-fold higher risk [odds ratio (OR) 3.86; 95% confidence interval (CI) 1.60–9.31; P=0.003] of voiding at least twice per night than those younger than 50 years. In the same model, patients with NI greater than 1.5 had a 4.5-fold higher risk of voiding at least twice per night (OR 4.59; 95% CI 1.80–11.17; P=0.001). FV charts are valuable for determining the cause of nocturia in women with LUTS. Our findings suggest that age and the NI may be important variables in the evaluation of nocturia in women with LUTS.