Association between Nocturnal Frequency and Erectile Function in Eugonadal Men with Benign Prostatic Obstruction: A Cross Sectional Study

PURPOSE: We aimed to evaluate the association between nocturnal frequency and erectile dysfunction in patients with benign prostatic obstruction. MATERIALS AND METHODS: To evaluate the association, we simultaneous evaluated urodynamic study, prostate ultrasound, nocturnal tumescence test (nocturnal penile tumescence) for sleep-related erection (SRE) and two questionnaires, international prostate symptom score (IPSS) and 5-item version of the international index of erectile function (IIEF-5). Patients with hypogonadism or nocturnal polyuria were excluded. RESULTS: Forty-six patients were registered over 4 years. The mean age, prostate size, IPSS score, and IIEF-5 score were 67.65±5.51 years, 65.10±22.12 mL, 24.67±7.89, and 9.50±7.01, respectively. Among the IPSS subscores, nocturia was most significantly related to the total IIEF-5 score (p<0.001). More severe nocturia was associated with less frequent SRE (p=0.003) and shorter total duration of SRE (p=0.002), which in turn elucidated that nocturia was significantly related to the total amount of rigidity signals (rigidity activity unit, RAU) or tumescence signals (tumescence activity unit, TAU). Among objective urodynamic parameters, bladder compliance also correlated to RAU and TAU. Individual subjective erectile function (IIEF-5) was significantly related to both RAU and TAU. CONCLUSIONS: Sleep fragmentation due to benign prostate obstruction related nocturnal frequency caused by reduced bladder compliance could decrease the frequency and duration of SRE, which decreases the total amount of SRE and reflects the patient's relevant erectile function.