C1QTNF9 and obstructive sleep apnea syndrome: Obstructive sleep apnea is closely related to the incidence and progression of CAD, and CTRP9 levels were negatively correlated with apnea levels; however, it was positively correlated with left ventricular ejection fraction in all participants, indicating that CTRP9 may play a role in the pathogenesis of CAD exacerbated by obstructive sleep apnea (Li et al., 2020).