Increase in bilirubin levels of patients with obstructive sleep apnea in the morning - A possible explanation of induced heme oxygenase-1

Study Objectives: In the absence of heme oxygenase-1 (HO-1), which catalyze s the oxidation of heme to generate carbon monoxide and indirect bilirubin, hypoxia induces severe right ventricular dilation and infarction. Despite severe hypoxemia during sleep, patients with obstructive sleep apnea-hypopn ea syndrome (OSAHS) rarely die during sleep. We hypothesized that apnea-rel ated hypoxemia would induce HO-1 and increase bilirubin levels in the morni ng in OSAHS patients. Therefore, bilirubin levels in OSAHS patients were an alyzed before and after nasal continuous positive airway pressure (nCPAP) t herapy. Design: Bilirubin levels in the afternoon before sleep and in the morning i mmediately after sleep were determined before and after nCPAP treatment. Setting: University Hospital in Kyoto, Japan. Patients: The subjects were 22 patients with OSAHS (mean (SEM) apnea and hy popnea index of 60 (5)) who were treated with nCPAP and 13 controls. Interv entions: N/A Measurements and Results: Before nCPAP treatment, total after-sleep bilirub in level was significantly higher than the pre-sleep level (p<0.0001). The difference between the serum indirect bilirubin levels in the morning versu s in the previous afternoon [D-(M-A)-IB] decreased significantly with nCPAP treatment (p<0.01). The magnitude of decrease in D-(M-A)-IB after nCPAP tr eatment correlated significantly with changes in the percent time spent wit h arterial O-2 saturation below 90% (r=0.44; p=0.04) and 85% (r=0.49; p=0.0 2), respectively, during sleep after nCPAP treatment. Conclusions: The increase in bilirubin level by HO-1 might protect OSAHS pa tients from disorders related to hypoxemia.