Some studies have shown that recurrent apnea during sleep in patients with OSAHS leads to hypoxemia, which promotes the release of various active substances, which in turn stimulates the release of endothelin-1 from endothelial cells, causes oxidative stress, reduces nitric oxide activities, and affects the remethylation process of HCY metabolism, resulting in abnormally elevated serum HCY levels (56). Here, EDN1 is linked to obstructive sleep apnea syndrome.