Background and objectiveObstructive sleep apnoea (OSA) is associated with an increased prevalence of metabolic syndrome. This study explores the effects of continuous positive airway pressure (CPAP) for patients with OSA on visceral and mesenteric fat thickness, carotid intima-media thickness (IMT) and adipokines. MethodsA randomized controlled study was conducted at a teaching hospital on 90 patients newly diagnosed with OSA to receive either therapeutic CPAP or subtherapeutic CPAP for 3months. Visceral fat thickness and carotid IMT were measured with B-mode ultrasound; adipokine levels were assessed at baseline and 3months. ResultsAltogether, 45 patients received therapeutic CPAP and 45 received subtherapeutic CPAP without significant differences in age 50.3 (10.1) versus 48.7 (9.0) years, BMI 28.2 (3.9) versus 28.2 (4.5) kg/m(2), Epworth Sleepiness Scale (ESS) 12.4 (5.9) versus 11.3 (4.7), apnoea-hypopnoea index (AHI) 30.6 (21.4) versus 35.2 (25.5) /h, minimum SaO(2) 79.6 (10.8) versus 76.7 (12.4) % and existing co-morbidities. CPAP usage was therapeutic 4.2 (2.1) versus subtherapeutic 4.1 (2.0) h/night over 3months. Adiponectin and irisin levels changed significantly following therapeutic CPAP for 3months versus subtherapeutic CPAP (-1.6 vs 7.3, P=0.042; 0.1 vs -0.1, P=0.028 respectively) while only serum level of monocyte chemotactic protein 1 (MCP-1) at baseline was positively correlated with AHI (r=0.278). No significant changes were observed in other adipokines, visceral fat thickness and IMT. ConclusionShort-term therapeutic CPAP versus subtherapeutic CPAP does not significantly reduce visceral fat thickness and IMT, although it reduces adiponectin and increases irisin. Obstructive sleep apnoea is associated with an increased prevalence of metabolic syndrome. This randomized, subtherapeutic continuous positive airway pressure (CPAP)-controlled study found no significant improvement in visceral fat and carotid intima-media thickness after 3months of CPAP therapy