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Introduction The association between obstructive sleep apnoea (OSA) and nocturia is well documented (Vrooman et al. Nat Rev Urol 2024; 21: 735–53). However, the prevalence of nocturia and the impact of continuous positive airway pressure (CPAP) on nocturia within the local service is unknown. It was hypothesised that CPAP would reduce the frequency of nocturia secondary to OSA.Methods 187 patients (117 males, median age 53yrs, range 21-90 yrs) had an initial sleep history taken to establish baseline symptoms including: nocturia frequency per night (minimum), presence of snoring, presence of morning headaches and Epworth Sleepiness Score (ESS) and a diagnosis of OSA established with a limited multi-channel sleep study (SOMNOmedics AG. SOMNOtouch™ PSG; 2024). Parameters recorded included apnoea hypopnea index (AHI), oxygen desaturation index (ODI) (≥3% dips/hour), mean oxygen saturation (SpO 2%) and percentage of time spent with SpO2<90%. The patients were initiated on CPAP therapy (ResMed Inc. AirSense 10 CPAP machine; 2023.) between 8 -12cmH2O. At both the 7-day review and the 4-week review data was documented (CPAP usage in days and hours, mask leak (L/min), and AHI (events per hour)).Data was analysed with Wilcoxon signed-rank, McNemar test, Pearsons’s chi square with univariate and multivariate logistic regression. Results were presented as either mean (+/- standard deviation) or median (range).Results Nocturia was associated with age (p = 0.034), ODI (p = 0.035), and % time SpO 2 spent <90% (p = 0.015). There was a significant difference in nocturia recorded before CPAP versus after CPAP (table 1). There was no significant difference in ESS between patients with nocturia and without nocturia after CPAP treatment. Increasing age was found to be associated with increased chance of having nocturia secondary to OSA.Conclusions CPAP therapy is associated with a reduction in nocturia in patients with OSA. Moderate to severe OSA is more likely to be associated with nocturia. Increasing age is associated as a significant predictor of having nocturia with a 3.2% increased likelihood of nocturia per year of age. No other measured factors were significantly associated with nocturia.Abstract P30 Table 1Effect of CPAP therapy on nocturia frequency