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 (Arl), 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 proinflammatory cytokine which additionally inhibits the anti-inflammatory effects of glucocorticoids. Thus, elevated MIF levels in OSA may contribute to elevated inflammation.