Although all insignificant (p > 0.05), both OSA severity markers correlated negatively with CHI3L1 levels within the lower BMI groups (< 30 kg/m2 and 30–35 kg/m2) but positively within the highest BMI group (BMI ≥ 35 kg/m2, Fig. S1a and Fig. S2a in supplement). This evidence concerns the gene CHI3L1 and obstructive sleep apnea syndrome.