Macrophage Migratory Inhibitory Factor (MIF) May Be a Key Factor in Inflammation in Obstructive Sleep Apnea

Study Objectives: This study investigated the 24-hour variation of macrophage migratory inhibitory factor (MIF), a cytokine which induces insensitivity to the anti-inflammatory effects of glucocorticoids, in patients with untreated obstructive sleep apnea (OSA) as compared to healthy adults with no OSA. Participants: Fifty-three men and women with OSA (mean apnea/hypopnea index [AHI] = 39.5) and 24 healthy adults (Non-OSA, AHI = 5.1). Measurements: Over a 24-h period, blood was collected every 2 h for MIF and cortisol determination. The following night, sleep was monitored with polysomnography. Results: MIF showed a strong 24-h variation, with a peak at 04: 00 and a nadir at 22:00. Patients with OSA showed 25% higher MIF levels (area under the curve) over 24 h than healthy controls. Furthermore, MIF levels were significantly associated with AHI and total arousal index (ArI), even after adjusting for BMI. Cortisol showed the expected 24-h variation (peaking at 06: 00), but no cortisol differences were observed between OSA and Non-OSA groups. Conclusion: MIF is elevated in patients with OSA and is related to OSA severity, while there was no difference in cortisol levels. MIF is a pro-inflammatory cytokine which additionally inhibits the anti-inflammatory effects of glucocorticoids. Thus, elevated MIF levels in OSA may contribute to elevated inflammation.