GDNF and obstructive sleep apnea syndrome: The IVW reported that higher levels of Eotaxin levels (OR=1.051, 95% CI, 1.096-1.008; P = 0.043), CUB domain-containing protein 1 levels (OR=1.043, 95% CI, 1.084-1.005; P = 0.043), and Interleukin-20 receptor subunit alpha levels (OR=1.090, 95% CI, 1.150-1.003; P = 0.011) were associated with an elevated risk of OSA, while higher levels of Glial cell line-derived neurotrophic factor levels (OR=0.954, 95% CI, 0.998-0.911; P = 0.049) and Thymic stromal lymphopoietin levels (OR=0.950, 95% CI, 0.999-0.903; P = 0.047) associated with a decreased risk of the disease.