Nocturia as a clinical marker of cardiovascular risk in obstructive sleep apnoea.

PURPOSE: Nocturia is commonly reported in obstructive sleep apnoea (OSA). Based on the underlying mechanism, involving atrial natriuretic peptide release from the cardiac atria in response to exaggerated intrathoracic pressure swings, we hypothesised that nocturia may serve as a clinical marker identifying individuals with increased cardiovascular disease (CVD) risk. METHODS: We analysed data from the Sydney Sleep Biobank for participants aged 30-74 years, with diagnosed OSA (AHI >5), with adequate data to calculate an office-based Framingham Risk Score (FRS) Nocturia was indicated on the Pittsburgh Sleep Quality Index. We compared cardiovascular risk scores between those with nocturia disturbing sleep 3 or more times per week, or less often. RESULTS: Six hundred and three patients with untreated OSA (67.5% male, mean age 54.2 years [SD 11.7], mean BMI 32.3 kg/m2 [SD 8.3]) were included. Fifty-one percent reported significant nocturia. Pre-existing CVD was reported in 12.4%, FRS was low in 13.6%, moderate in 38.6%, and high in 35.3%. Nocturia was significantly associated with increased cardiovascular risk and existing CVD (χ2 = 15.9, p < 0.001). On logistic regression, nocturia was associated with high CVD risk (OR 1.79, 95% CI 1.26-2.55) and this remained significant even with consideration of potential confounders (OR 1.72, 95% CI 1.18-2.53). On sex-stratified logistic regression this association remained significant in men (2.48; 1.62-3.81) but was not observed in women (0.96; 0.47 - 1.98). CONCLUSION: Nocturia may represent a readily identifiable clinical phenotype associated with elevated cardiovascular risk in men with OSA, although prospective studies are required to confirm its predictive value.