MDK and obstructive sleep apnea syndrome: Recent studies have shown that individuals at high risk for lung cancer with moderate-to-severe OSA have elevated expression of MDK (non-OSA: 1536 pg/mL, 95% CI 840–2360 pg/mL; moderate-to-severe OSA: 5902 pg/mL, 95% CI 816–8337 pg/mL) (85).