AIP and obstructive sleep apnea syndrome: Investigating lipid levels according to OSA severity, there was no difference in TC (p = 0.21) or LDL-C (p = 0.77), while progressively increasing triglyceride (p < 0.001) and AIP (p < 0.001) and progressively decreasing HDL-C (p < 0.001) levels were noted in OSA (Figure 1).