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Clinical predictors of nocturia in the sleep apnea population

By O.A. Raheem, R.K. Orosco, T.M.Davidson and C. Lakin.

Urology Annals, Volume 6, Issue 1, January 2014, Pages 31-35

Editor’s comments:
The aim of the present study was to show that nocturia is a potentially complex comorbidity in patients with obstructive sleep apnea (OSA). It is not yet fully clear why patients with OSA can suffer from nocturia. However, it has been hypothesized an important role for the Atrial Natriuretic Peptide, whose secretion from the right atrium increases when the altered respiratory pattern generates hypoxia. This, in turn, induces the kidney to increase the glomerular filtration rate which leads to an increased urinary output. In the study, 100 patients with OSA and no symptoms of nocturia have been compared to 100 patients affected by OSA and nocturia. After performing a multivariate analysis, two different risk factors for the development of nocturia in OSA patients have been identified: age and high  Apnea–Hypopnea Index (AHI). According to these results, the Authors strongly suggest to  practicing urologists to  take into account the presence of sleep apnea in old- or young-aged patients who are complaining of nocturia. But the converse is equally important: patients with sleep apnea should be evaluated for LUTS/BPH and nocturia symptoms, as they may require specialist evaluation for such.

Abstract
Objectives: 

This study aims to evaluate clinical predictors of nocturia in patients with obstructive sleep apnea (OSA).

Materials and Methods: 
In retrospective manner, a total of 200 patients with OSA were randomly included. Group I contained 100 patients with OSA and no nocturia, and Group II included 100 patients with OSA and nocturia. Bivariate logistic analyses were used to identify variables most likely to contribute to nocturia. Multivariate logistic regression of age, waist circumference, STOP score (Snore, Tired, Obstruction and Pressure), and Apnea-Hypopnea Index (AHI) was performed to evaluate predictors of nocturia. Statistical significance was defined as P0 < 0.05.

Results: 
Median nocturia episodes were 2.2 in Group II. Patients were younger in Group I, with a mean age of 45 vs 50 years (P = 0.008). Mean BMI of 30 was similar in both groups, but there were more overweight patients in Group II (28% vs18%). AHI approached significance between groups-18 vs 23 in group I and II, respectively (P = 0.071). In multivariate analysis, age over 70 years and moderate AHI were statistically significant predictors of nocturia (coefficients 0.6 and -0.2 with P = 0.003 and 0.03, respectively).

Conclusions: 
This study identifies age and AHI score as predictors of nocturia in patients with OSA. This may indicate the usefulness of incorporating nocturia in the screening of patients with OSA. Future studies are needed to further evaluate mechanism of action, clinical significance, and effect of treatment for nocturia in patients with OSA.