C1QTNF9 and obstructive sleep apnea syndrome: Plasma CTRP9 concentrations were significantly decreased in the moderate/severe OSA group than in the no/mild OSA group (4.7 [4.1-5.2] ng/mL vs. 4.9 [4.4-6.0] ng/mL, P = 0.003) (Table 1 and Figure 2(a)).