HIF1A and obstructive sleep apnea syndrome: Clinical studies have found that serum levels of hypoxia-inducible factor HIF-1α are significantly higher in patients with obstructive sleep apnea (OSA) who develop postoperative delirium (p < 0.01); elevated HIF-1α is an independent risk factor for PD (OR = 4.82) (Breitkopf et al., 2025).