Sleep duration is an independent factor in nocturia: analysis of bladder diaries

OBJECTIVE To analyse the relationship between the number of nocturia episodes and other variables obtained from a bladder diary, with special attention to the duration of sleep, as nocturia is closely related to sleep disorders. PATIENTS, SUBJECTS AND METHODS Between April 2005 and December 2006, 532 participants, including both community-dwelling subjects who underwent a mass screening programme and outpatients who consulted the department of urology, completed a 3-day bladder diary. Clinical variables, i.e. the number of daytime and night-time voids, diurnal and nocturnal urine volume, daytime and night-time maximum voided volume, sleep duration and nocturnal polyuria index (NPi) were obtained from the diary. The variables were assessed by univariate analysis in all participants, and by multiple regression analysis of all participants, males, females, subjects in mass screening and those with no 24-h polyuria, to determine which variables were independently associated with the number of nocturia episodes. RESULTS Univariate analysis showed a considerable correlation between the nocturia episodes and age, nocturnal urine volume, NPi and sleep duration. On multiple regression analysis, age, nocturnal urine volume, night-time maximum voided volume and sleep duration were independently related to number of nocturia episodes in all subgroups. CONCLUSIONS Sleep duration was confirmed as an independent factor in nocturia. Sleep conditions, including sleep duration, should be considered when evaluating and treating patients with nocturia.