Notably, FSTL1 levels were not influenced by obesity (obese: 11,045.46 ± 265.51 ng/mL vs. non-obese: 11,458.37 ± 618.22 ng/mL; p = 0.544), indicating that the associations between FSTL1 and OSA severity are obesity-independent. This evidence concerns the gene FSTL1 and obstructive sleep apnea syndrome.