Correlation of salivary cortisol level with obstructive sleep apnea syndrome in pediatric subjects

ObjectiveObstructive sleep apnea syndrome (OSAS) is associated with stress system activation involving the hypothalamic–pituitary–adrenocortical (HPA) axis. The relationships among salivary cortisol, a measure of the HPA axis, and objective parameters of polysomnography (PSG) and subjective sleep symptoms were examined.MethodsOur prospective study enrolled 80 children who had a physical examination, underwent overnight PSG, and completed the Korean version of the modified pediatric Epworth sleepiness scale (KMPESS) and OSA-18 (KOSA-18) questionnaires. Saliva was collected at night before PSG and in the early morning after PSG.ResultsSubjects (N = 80) were divided into control (n = 32, apnea–hypopnea index [AHI] < 1) and OSAS (n = 48, AHI ⩾ 1) groups; the OSAS group was subdivided into mild (1 ⩽ AHI < 5) and moderate to severe (AHI ⩾ 5) groups. Although salivary cortisol before PSG (n-sCor) did not show a significant change with OSAS severity, salivary cortisol after PSG (m-sCor) significantly decreased with OSAS severity. This decrease resulted in a salivary cortisol ratio (r-sCor) that was significantly different between the control group and the two OSAS subgroups. The m-sCor and sub-sCor of the total group as well as the m-sCor, sub-sCor, and r-sCor of the OSAS group were negatively related to the oxygen desaturation index (ODI). The m-sCor and r-sCor in the OSAS group also were related to subjective sleep symptoms (quality of life [QOL] by KOSA-18).ConclusionsAmong the four salivary cortisol parameters, r-sCor was negatively associated with OSAS severity, ODI, and QOL (KOSA-18), which may indicate a chronically stressed HPA axis. These results demonstrate that salivary cortisol may be a useful biomarker of OSAS.