Prevalence of nocturia in sleep-disordered breathing and its correlation with severity of the disease

Nocturia is a common complaint in the general population and prevalence varies across studies. It not only causes significant sleep disruption and daytime consequences such as impaired concentration and fatigue but also is independently associated with the risk of cardiovascular morbidity. Nocturia may be associated with various disorders includingsleep-disordered breathing (SDB). The mechanism by which SDB causes nocturia is not clear from the various studies conducted so far.Several different hypotheses suggesting various different mechanisms have been proposed. A systematic large-scale study of the association between nocturia and SDB indicating its prevalence and association with its severity has not been performed.

To investigate the occurrence of nocturia in SDB,identify its prevalence and explore its correlation with severity of the disease.

A prospective case-controlled study was conducted among 150 adult patients of SDB with obstructive sleep events, along with 150 age- and sex-matched healthy adult controls. The cases were subclassified into mild (respiratory disturbance index [RDI] ≥5–15/h), moderate (RDI ≥15–30/h) and severe (RDI ≥30/h) categories comprising 50 patients each. Scoring was done and the diagnosis was made in accordance with the latest American Academy of Sleep Medicineguidelines. Both cases and controls were evaluated for the presence of nocturia, pathological nocturia (PN) and frequency of nocturia througha common questionnaire. Nocturia was defined as self-reported awakening at least once per night to urinate, while PN was defined as awakening at least twice per night to urinate. Statistical analysis was carried out using SPSS 16.0 (SPSS Inc., Chicago, IL USA) and GraphPad Prism 6.01 software and a p value of <0.05 was considered as statistically significant.

Nocturia was found to be present in more than 4/5of the patients, and half of the patient population had PN (p<0.0001). The mean frequency of nocturia in patients was 1.75±1.29 and that in the control group was 0.51±.071 (p<0.0001). Nocturia was found to be more common in females compared with males. The prevalence of PN differed significantly (p<0.05) between various severities of SDB, thereby showing an increase in the frequency with increasing severity of the disease. The correlation between severity of SDB and frequency of nocturia was also found to be positive (p<0.001).

Nocturia and PNare more commonin patients of SDB as compared to the general population, and more commonly seen with increased severity of SDB. The frequency of nocturia shows an independent positive correlation with severity of SDB irrespective of the presence of various confounders for nocturia. High prevalence of both PN and SDB in the population suggests the likelihood of the presence of a large percentage of patients with nocturia having concomitant SDB.