SERPINE1 and obstructive sleep apnea syndrome: In the group of patients with OSA, there was a significant positive correlation between plasma PAI-1 concentrations and AHI (r = 0.40; p = 0.006), AI (r = 0.42; p = 0.004), RDT (r = 0.38; p = 0.01), and DI (r = 0.39; p = 0.009).