In a retrospective cohort, Cao et al. [29] found significantly higher AIP values in higher severities of OSA (controls: 0.01 ± 0.21, mild OSA: 0.14 ± 0.30, moderate OSA: 0.24 ± 0.33, and severe OSA: 0.36 ± 0.30; P < 0.001). Here, AIP is linked to obstructive sleep apnea syndrome.