Obstructive sleep apnoea syndrome (OSA) is a respiratory disorder characterised by repeated episodes of prolonged upper airway obstruction during sleep. It has a prevalence of 1–5% in children and can occur at any age. Overnight polysomnography (PSG) is currently considered the gold-standard diagnostic technique. Hypoxaemia sets the presence, risk and progression of many diseases. Several haematological responses to hypoxaemia have been described. Of these, an increased red cell distribution width (RDW) seems to be the most persistent over time. RDW describes the volume heterogeneity of the circulating red blood cell population, and the calculation of this parameter is based on the mean corpuscular volume (MCV).
A review revealed that increased RDW >14% is predictive of poor outcome for certain diseases and no difference in RDW has been reported between sexes. Several factors may increase RDW, and the one with the greatest impact is erythropoietin production Intermittent hypoxia stimulates erythropoietin synthesis and secretion. Increases in endogenous erythropoietin production have been associated with an increase in RDW in patients with coronary disease.
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