To examine the frequency of and risk factors for nocturia in patients with symptomatic benign prostatic hyperplasia (BPH), and the degree of improvement of nocturia after treatment for BPH.

A total of 505 consecutively selected, newly diagnosed patients with symptomatic BPH were evaluated in studies examining frequency of and risk factors for nocturia. We analyzed the relationships between nocturia assessed by International Prostate Symptom Score (IPSS) and other parameters, including age, prostate volume, serum prostate-specific antigen level, and uroflow variables. Other studies examining the impact of conservative and invasive treatments on nocturia were also conducted using 165 patients receiving tamsulosin and 138 undergoing transurethral resection of the prostate (TURP).

Overall, 359 of the 505 patients (71.1%) answered that they arose at least twice for urination at night. Patient age, score of urgency, and functional bladder capacity were each significantly associated with nocturia. Tamsulosin therapy and TURP significantly reduced the number of episodes of nocturia in 17.9% and 32.2% of patients, respectively. These rates of improvement were lowest for nocturia among the seven individual symptom scores.

In this study using selected cohorts, the frequency of nocturia in patients with BPH was higher than that in community-based studies. Although we cannot estimate patients’ satisfaction by the observed changes in scores, the rates of improvement were lowest for nocturia among the seven symptoms of IPSS after conservative and invasive treatments for BPH.