Correlation of changes in the red blood cell distribution width with the response to continuous positive airway pressure in patients with obstructive sleep apnea

It is recently found that the red blood cell distribution width (RDW) is independently associated with cardiovascular disease in patients with obstructive sleep apnea (OSA).The goal of this study is to investigate the correlation of RDW with the severity of OSA and whether RDW could be used to monitor the response to continuous positive airway pressure (CPAP) therapy in OSA patients. The study enrolled 70 participants. Control group (n = 24) consisted of patients with normal polysomnography and OSA group (n = 46) comprised patients with OSA of varying severity. RDW was measured before polysomnography in both groups. In addition, RDW was measured in the OSA group following 3 months of CPAP therapy. The RDW was significantly higher in the OSA group (p < 0.001), and this difference remained after adjusting for age and body mass index (p = 0.001). The RDW was approximately twofold greater in the OSA group (OR 2.126, 95% confidence interval 1.32–3.41; p = 0.002). On univariate analysis, the RDW was significantly correlated with hypoxia parameters, which was persistent with multivariate analysis. Furthermore, CPAP therapy reduced RDW (p = 0.002), and the change in the severity of 3% ODI by CPAP was correlated with the change in the RDW (r = 0.416, p = 0.013). The high RDW may be related to the pathophysiology of OSA. The high RDW in OSA may be associated with hypoxia. Therefore, treating OSA with CPAP could improve the RDW.