Correlation Between Salivary Alpha-Amylase Level and Heart Rate Variability in Pediatric Subjects with Sleep-Disordered Breathing

Background and Objectives: The aim of this study was to evaluate the relationship between salivary alpha-amylase (sAA) and heart rate variability (HRV) indices in SDB children based on objective parameters of polysomnography (PSG). Materials and Method: This prospective study enrolled 67 children who underwent a physical examination and full-attended in-lab PSG with continuous electrocardiographic signal. The sAA were measured at night before PSG and in the early morning after PSG. Results: The subjects were divided into control [n=26, apnea-hypopnea index (AHI)≤1] and obstructive sleep apnea syndrome (OSAS, n=41, AHI＞1) groups; the OSAS group was subdivided into mild (1＜AHI≤5), moderate (5＜AHI≤10), and severe (10＜AHI) groups. The severe OSAS group was significantly different from the control and other OSAS subgroups in terms of the ratio between the low- and high-frequency components (LF/HF ratio) among the HRV indices. The LF/HF ratio was positively correlated with the sAA ratio and sAA subtraction (r=0.271; r=0.347). Conclusion: TAlthough both HRV and sAA were useful methods of predicting severe OSAS in children, a weak correlation between HRV and sAA was shown in pediatric OSAS subjects. Therefore, HRV and sAA may be independent parameters revealing different aspects of pediatric OSAS.