Circulating IGFBP-7 in Obstructive Sleep Apnea: A Single-Cohort Preliminary Assessment of Its Diagnostic Performance and Post-Treatment Dynamics

Background/Objectives: Obstructive sleep apnea (OSA) is a sleep condition characterized by intermittent hypoxia, systemic inflammation, and metabolic dysfunction. Contemporary diagnosis criteria depend on polysomnography (PSG), a procedure that is limited by cost and accessibility. Identifying reliable circulating biomarkers may facilitate disease diagnosis and treatment monitoring. Methods: Insulin-like growth factor binding protein-7 (IGFBP-7) has been implicated in pathways relevant to OSA, although its precise role remains elusive. While we previously identified IGFBP-7 as a candidate of interest, in this report, we assessed circulating IGFBP-7 levels in a single-cohort study of 164 participants (124 with OSA, 40 controls) at the Dasman Diabetes Institute. A Type I PSG test was performed in a level 1 sleep laboratory to diagnose sleep apnea. Among the 124 patients with OSA who underwent multilevel sleep surgery (MLS), 67 completed the 3-month postoperative follow-up and were included in the longitudinal analyses. In these participants, we evaluated the apnea–hypopnea index (AHI) at baseline and 3 months after surgery and examined the associations between circulating IGFBP-7 levels, OSA severity indices, and metabolic parameters. Results: Our data revealed a significant increase in IGFBP-7 levels in people with OSA compared to controls (p < 0.001). Importantly, the increase in IGFBP-7 was positively correlated with AHI (r = 0.272, p < 0.001), indicating a potential link with this condition. IGFBP-7 levels declined significantly following MLS (p < 0.001), paralleling improvements in AHI and suggesting responsiveness to therapeutic intervention and a reduced hypoxic burden. IGFBP-4 levels increased significantly in patients with OSA (p = 0.006) but were not correlated with IGFBP-7. The receiver operating characteristic (ROC) analysis identified IGFBP-7 with a cut-off value of 14,003.21 pg/mL as a potential biomarker for OSA, with moderate performance (AUC = 0.722, 95% CI: 0.636–0.808; sensitivity 73%, specificity 84%). Notably, combining IGFBP-7 with IGFBP-4 resulted in a modest improvement (AUC = 0.755). Conclusions: Our data suggest that IGFBP-7 shows a modest association with OSA severity and may have exploratory value as part of a multi-marker or risk-stratification approach. Further large-scale and longitudinal studies are warranted to extensively explore the potential utility of IGFBP-7 within multi-marker approaches.