Furthermore, subgroup analyses based on different study designs revealed reduced plasma/serum IGF-1 concentrations in patients with OSAHS in cross-sectional, case-control, and cohort studies, indicating that in most reports, the serum/plasma IGF-1 concentrations in patients with OSAHS were reduced compared with those of control groups and that IGF-1 concentration may be related to OSAHS onset. Here, IGF1 is linked to obstructive sleep apnea syndrome.