Neutrophil-to-lymphocyte ratio in obstructive sleep apnea; a multi center, retrospective study

Systemic inflammation is important in pathophysiology of obstructive sleep apnea (OSA) and its comorbidity. Neutrophil to lymphocyte ratio (N/L ratio) is a novel inflammation index that has been shown to independently predict poor clinical outcomes. In this study, we aimed to evaluate the role of N/L ratio in OSA patients and comparing with other well-known inflammatory marker, C-reactive protein (CRP).

We conducted a retrospective analysis of 481 patients with mild, moderate and severe OSA (163,158 and 160 patients, respectively) and leukocyte profiles of 80 sex-, age- and body mass index- matched healthy controls. Patients were excluded if they had underlying cancer, chronic inflammatory disease, any systemic infection, uncontrolled hypertension and diabetes mellitus, a known acute coronary syndrome, valvular heart disease, a known thyroid, renal or hepatic dysfunction.

We found that N/L Ratio in severe OSA patients was significantly higher compared with mild, moderate, OSA patients and healthy controls (p < 0.001). However, there was no difference between mild and moderate OSA patients (p = 0.636). There was also no significant difference between mild-moderate OSA patients and healthy groups (p = 0.150). CRP levels were not different in all OSA stages (p = 0.595). By Spearman correlation, there was no correlation between CRP and N/L ratio.

N/L ratio, which is quick, cheap, easily measurable novel inflammatory marker with routine complete blood count analysis, is a surrogate marker of obstructive sleep apnea severity.