Hypoxia and inflammation indicate significant differences in the severity of obstructive sleep apnea within similar apnea-hypopnea index groups

Abstract

Purpose: We determined whether hypoxia parameters are associated with C-reactive protein (CRP), mean platelet volume (MPV), white matter hyperintensity (WMH), and the severity of obstructive sleep apnea (OSA), and also evaluated whether hypoxia parameters, CRP, MPV, and WMH differ in patients with similar apnea-hypopnea index (AHI) scores. Methods: A total of 297 patients, who were evaluated using polysomnography, were assessed retrospectively. The measured hypoxia parameters included total sleep time with oxygen saturation <90% (ST90), percentage of cumulative time with oxygen saturation <90% (CT90), and lowest oxygen saturation (min SaO2). The patients were divided into subgroups according to their CT90 values, and patients with different AHI severities were divided into subgroups according to their ST90 and min SaO2 levels. Results: Hypoxia parameters are associated with CRP, MPV, WMH, and the severity of OSA (P < 0.05). The hypoxia parameters differed in all subgroup analyses of similar AHI groups (P < 0.001), and CRP differed only in severe OSA (P < 0.008, P < 0.001). In subgroup analyses of similar AHI groups, MPV and WMH were not significantly different (P > 0.05). Above the hypoxia threshold (CT90 ≥ 10%) of CRP, MPV increased significantly and the presence of WMH increased twofold. Conclusions: These data suggest that increased hypoxia severity may mediate increased inflammation and activation of platelets and contribute to the pathogenesis of WMH in patients with OSA. In addition, patients with severe OSA may show significant variability in inflammation and vascular risk. Further prospective data are needed.