Introduction
Nocturia is a common condition especially in aging population and is defined as the complaint of waking at night one or more times to void.1 The definition has been recently updated as to sleep or intent to sleep after each voiding period which should be demonstrated by a bladder diary.2 There is growing evidence in the last decade that nocturia is not only a part of diseases affecting the lower urinary tract such as benign prostatic hyperplasia (BPH) and overactive bladder (OAB), but a distinct entity which may arise from several other medical conditions.3 One of the possible mechanisms mostly included is nocturnal polyuria (NP) defined as the excessive urine production at night while asleep; > 33% of the 24-hour urine production in patients >65 years and > 20% of the 24-hour urine production in younger patients.4 Global polyuria (24-hour urine volume > 40 ml/kg), reduced bladder capacity due to lower urinary tract dysfunction and primary / secondary sleep disorders constitute the other mechanisms. These different mechanisms need to be explored in all patients presenting with nocturia in order to provide the best treatment approach. However, it is not always possible or easy to obtain a detailed bladder diary in daily clinical practice which is essential for differentiating between afore-mentioned various pathophysiological mechanisms.
Nocturia has negative impacts on quality of life (QoL) of patients and these impacts are mostly related with the severity of nocturia. Some of the studies concluded that two or more nocturia episodes lead to bother from nocturia and the degree of bother was associated with severity of nocturia.5,6 However there is no consensus on nocturia severity and its impact on QoL of patients and there are few studies in the existing literature evaluating the mechanisms of nocturia. So, we aimed to identify pathophysiological mechanisms of nocturia and seek whether proposal of nocturia grading helps for differentiation of the various pathologic conditions.