Nocturnal polyuria may decrease the treatment efficacy of overactive bladder syndrome (OAB); and adjuvant medication, such as desmopressin, may be needed for the treatment of nocturnal polyuria. The knowledge of prevalence and risk factors of nocturnal polyuria might be important for the treatment on OAB. Thus, our aim is to describe prevalence and risk factors of nocturnal polyuria in women with OAB.

Between July 2009 and January 2018, all women with OAB visiting a medical center for evaluation were reviewed. The classification of OAB-wet or OAB-dry is based on the record of three-day bladder diary of each patient. The diagnosis of OAB in each patient was based on the presence of at least one episode of urgency in her three-day bladder diary and with the absence of stress urinary incontinence. The presence of at least one episode of urgency associated incontinence was defined to be OAB-wet, otherwise, OAB-dry.  
       Nocturnal polyuria was defined when the proportion of nighttime voided volume over 24-hour voided volume was greater than 33% for ≥65 year-old women, and when the proportion of nighttime voided volume over 24-hour voided volume was greater than 20% for <65 year-old women.

A total of 1,071 women with OAB, including 203 (19.0%) OAB-wet and 868 (81.0%) OAB-dry women, were included in this study. 
       The rates of nocturnal polyuria were 35.9% (257/715) in <65 year-old women, and 17.4% (62/356) in ≥65 year-old women (Table 1).
       Factors predicting nocturnal polyuria included age, parity, OAB-wet, daytime frequency and nocturia episodes (Table 2).
       Receiver operating characteristic curve analysis revealed nocturia episodes ≥ 5 in the three-day bladder diary was an optimal cut-off value to predict nocturnal polyuria (sensitivity = 85.6%, specificity = 61.0%; area = 0.80, 95% CI = 0.77 to 0.82). The areas under the curve of age, parity, OAB-wet and daytime frequency were only 0.57 (95% CI = 0.53, 0.60), 0.56 (95% CI = 0.52, 0.60), 0.53 (0.50, 0.55) and 0.57 (0.53, 0.61), respectively.

Nocturnal polyuria was not uncommon in women with OAB. However, nocturia episodes remained the only useful factor to predict nocturnal polyuria.

Nocturnal polyuria is not uncommon in women with OAB, especially in women with ≥ 5 nocturia episodes in her three-day bladder diary. In addition to standard pharmacotherapy for OAB, adjuvant therapy for OAB women with ≥ 5 nocturia episodes in three days might be needed for better treatment efficacy