Neither OSA nor OSA severity in terms of AHI, ODI, lowest SpO2, and time spent below 90% SpO2 were associated with high MPO and high MMP-9 values in the entire cohort (Table 3 and Table 4); the results were similar in the sensitivity analysis after excluding patients with current smoking at baseline. The gene discussed is MMP9; the disease is obstructive sleep apnea syndrome.