Red cell distribution width and uric acid in patients with obstructive sleep apnea

Abstract

Background: Obstructive sleep apnea (OSA), characterized by recurrent partial or complete pharyngeal closure, resulting in apnea or hypopnea, is closely associated with cardiovascular disorders (CVDs). Elevated red cell distribution width (RDW) and serum uric acid (SUA) levels have also been associated with CVDs and the consequent mortality. The aim of this study is to determine SUA levels and RDW in patients with OSA which is major a risk factor for CVDs.

Methods: This was a retrospective study involving 600 subjects evaluated by polysomnography. Patients were grouped according to the apnea-hypopnea index (AHI), expressed as control group or as mild OSA, moderate OSA, and severe OSA groups.

Results: The mean RDW and the mean SUA were significantly higher in the severe OSA group than in all other groups (P < .015 and P < .003, respectively, for all). RDW was negatively correlated with minimum S_pO2 (r = -.142, P < .01) and positively correlated with mean oxygen desaturation time (r = .113, P < .05). SUA was negatively correlated with minimum S_pO2 (r = -.229, P < .01). The RDW was significantly higher in the OSA patients with CVDs than in those with OSA only (P < .05), although there was no significant difference between the OSA patients with and without CVDs in terms of the SUA in any of the groups (P > .05).

Conclusions: Elevated levels of SUA and RDW were associated with OSA severity, as defined by AHI. In addition, RDW was significantly higher in severe OSA with CVDs.

Keywords: cardiovascular disorders; obstructive sleep apnea; red cell distribution width; uric acid.