Prevalence of obstructive sleep apnea detected by the Berlin Questionnaire in patients with nocturia attending a urogynecology unit

Nocturia has been associated with several chronic conditions including obstructive sleep apnea (OSA). The pathophysiological link between nocturia and OSA has been well delineated, but the prevalence of this condition in patients with nocturia is unknown. The aim of this study was to determine the prevalence of sleep apnea in patients with nocturia compared with patients without nocturia in a group of women referred to a urogynecology unit. After ethics approval, a cross-sectional case control study including 81 cases and 79 controls was conducted. The sample size of 72 patients was required for each arm to detect a 23 % difference in the prevalence of OSA with a 95 % confident interval (CI) and statistical power of 80 %. All patients completed the Nocturia, Nocturia Enuresis and Sleep Interruption Questionnaire (NNES-Q) and the Berlin OSA Questionnaire. The NNES-Q was used to define cases and controls. The Berlin Questionnaire was used to classify patients as being at a high or a low risk of having OSA. Univariate analysis was first performed, followed by logistic regression to assess the association between nocturia and OSA, as well as other possible variables associated with nocturia. Fifty of the cases (61.7 %) were classified as being at a high risk of having OSA compared with only 19 (24.1 %) in the control group (OR 2.9, 95 % CI 1.29-6.52, p = 0.01). Other variables found to be statistically significant by logistic regression were high BMI, overactive bladder, and low bladder capacity (< 300 cc). Patients with nocturia showed a significantly higher risk of having OSA. Patients with nocturia should be screened for OSA.