Nocturia and snoring: Predictive symptoms for obstructive sleep apnea

Purpose: Current screening for obstructive sleep apnea (OSA) emphasizes self-reported snoring and other breathing symptoms. Nocturia, a symptom with a precise pathophysiological link to sleep apnea, has not been assessed as a screening tool for this common disorder of sleep respiration. In a large sample of adults presenting to area sleep centers, we aimed to determine the predictive power of nocturia for OSA and compare findings with other markers of OSA commonly used to screen for this disease. Methods: This was a retrospective chart review. A consecutive sample of 1,007 adult patients seeking treatment at two sleep centers in New Mexico completed detailed medical and sleep history questionnaires and completed diagnostic polysomnography testing. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of nocturia, snoring, high body mass index, sex, and age for OSA were determined. Hierarchical linear regression determined unique variance contribution to the apnea-hypopnea index, the objective measure of sleep apnea severity. Results: The results are as follows: sensitivities - snoring, 82.6% and nocturia, 84.8%; specificities - snoring, 43.0% and nocturia, 22.4%; PPVs - snoring, 84.7% and nocturia, 80.6%; and NPVs - snoring, 39.6% and nocturia, 27.9%. With hierarchical linear regression, patient-reported nocturia frequency predicted apnea-hypopnea index (OSA severity) above and beyond body mass index, sex, age, and self-reported snoring (P<0.0001). Conclusions: Nocturia appears comparable to snoring as a screening tool for OSA in patients presenting to a sleep medical center. Research in urology and primary care clinics is needed to definitively clarify the use of nocturia as a screening instrument for obstructive sleep apnea.