Association of elevated levels of vascular endothelial growth factor in obstructive sleep apnea syndrome with patient age rather than with obstructive sleep apnea syndrome severity

Background: Although certain studies report high levels of vascular endothelial growth factor (VEGF) in obstructive sleep apnea syndrome (OSAS), the effect of systemic hypoxia on circulating VEGF remains controversial. Objectives: To study the association of serum VEGF and OSAS in a large group of patients. Methods: One hundred patients with OSAS (mean age 58.1 ± 12.4 years, mean body mass index 30.6 ± 5.4 kg/m²) were tested for serum VEGF levels, and the findings were correlated with the severity of OSAS, as determined by the apnea-hypopnea index (AHI) on the basis of polysomnography and background data. Results: The mean AHI was 40.0 ± 21.2 (range 10-106). Mean minimal oxygen saturation was 80.6 ± 11.7% (range 43-98%) and mean time of oxygen saturation under 90% was 50.0 ± 75.0 min (range 0-300 min). The mean VEGF level was 445.2 ± 289.8 pg/ml in the study group (vs. 280 pg/ml reported in normal controls). The mean platelet count was 233.8 ± 64.4 10³/ml and the mean VEGF/platelet ratio was 1.95 ± 1.40 pg/10⁶. There was no association of VEGF or VEGF/platelets with the severity of OSAS. However, both factors showed a significant correlation with patient age (r = 0.224, p = 0.01 and r = 0.425, p = 0.01, respectively). Age was the only parameter to significantly predict VEGF and VEGF/platelets on multivariate analysis (R² = 0.713, p = 0.001 and R² = 0.844, p = 0.001, respectively). Conclusion: The elevation of serum VEGF in OSAS is not associated with the severity of the disease, but it is associated with patient age. VEGF might be involved in the long-term adaptive mechanism in OSAS, and its age-dependent increase might partly explain the reduced mortality in elderly OSAS patients.