CXCL8 and obstructive sleep apnea syndrome: As a result, we did not find any significant causal relations of OSA on IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-17, and IL-18 by the primary method of IVW but the result of IL-5 was almost significant [estimate: 0.267 (−0.030, 0.564), p = 0.078] (Figure 4B).