Different prognosis between severe and very severe obstructive sleep apnea patients; Five year outcomes

Background: Obstructive sleep apnea (OSA) is characterized by augmented sympathetic nerve activity. In our previous study, patients with OSA and an apnea-hyperpnea index (AHI) > 55 events/h showed increased single-unit muscle sympathetic nerve activity compared to patients with OSA and AHI of 30–55 events/h. However, the prognostic impact in these patients remains unclear. Methods: Ninety-one OSA patients were included. All patients who had indication for continuous positive airway pressure (CPAP) were treated with CPAP. Patients were divided into three groups: mild/moderate OSA (S), AHI < 30 events/h (n = 44); severe OSA (SS), AHI 30–55 events/h (n = 29); and very severe OSA (VSS), AHI > 55 events/h (n = 18). The primary endpoint was a composite outcome composed of death, cardiovascular events, stroke, and heart failure with hospitalization. Results: In the 5-year follow-up, the primary event rate in the SS group [3 events (7%)] was the same as that in the S group [3 events (10%)]. However, the VSS group showed a significantly higher primary event rate among the three groups [6 events (33%), p < 0.05]. In Cox regression analysis, the VSS group had the highest hazard ratio compared to other risk factors. Conclusions: CPAP was effective for preventing cardiovascular disease in patients with severe OSA, however patients with very severe OSA still had a high event rate, indicating that CPAP treatment might be insufficient to reduce the OSA-related risk burden in patients with very severe OSA. Additional systemic medical treatment for CPAP might be needed in patients with very severe OSA.