Changes in cortisol levels by continuous positive airway pressure in patients with obstructive sleep apnoea: Meta-analysis of 637 individuals.

Background Obesity, obstructive sleep apnoea (OSA) and hypertension frequently coexist and are associated with elevated cortisol levels. Identification and treatment of such patients is important when investigating for suspected Cushing's syndrome and hypertension. Studies of the impact of continuous positive airway pressure (CPAP) on cortisol and blood pressure are limited by small sample size and show conflicting findings. We conducted a meta-analysis to document changes in the levels of cortisol and blood pressure in response to CPAP treatment of OSA. Methods Meta-analysis was conducted using RevMan (v5.3) and expressed in standardised mean difference (SMD) for catecholamines and mean difference (MD) for systolic (SBP) and diastolic blood pressure (DBP). The quality of the studies was evaluated using standard tools for assessing the risk of bias. Results A total of 22 studies met our search criteria; they consisted of 16 prospective cohort studies (PCS) that recruited 385 participants and six randomized control trials (RCT) totalling 252 participants. Range of mean age was 41-62yr and BMI 27.2-35.1kg/m2 . CPAP treatment reduced plasma cortisol levels in PCS: SMD = -0.28 (95%CI = -0.45 to -0.12), I 2 = 0%, p = 0.79 and in RCT: SMD = -0.39 (95%CI = -0.75 to -0.03), I 2 = 28.3%, p = 0.25. CPAP treatment reduced SBP by 5.4 mmHg (95% confidence interval =1.7-9.1) and DBP by 3.3 mmHg (95% confidence interval = 1.0-5.7). Inter-study heterogeneity was low for all studies. Bias in most RCT arose from the lack of blinding of participants and personnel. Conclusion CPAP treatment in individuals with OSA reduces cortisol levels and blood pressure. This article is protected by copyright. All rights reserved.