Respiratory depression during sleep is a major health challenge after surgery. The main cause is reduction in breathing due to opioids, which are commonly used for management of postoperative pain. The consequences are hypoxemia and hypercapnia, which may increase the risk of cardiovascular complications, mortality, and healthcare utilization. Identifying individuals who are at risk of postoperative respiratory depression prior to the surgery can help guide the perioperative care to reduce adverse outcomes. In this project, we developed a risk assessment model to identify individuals at risk of postoperative respiratory depression prior to the surgery, based on the demographics and changes in preoperative overnight oxyhemoglobin saturation (SpO