[Characteristics of sleep apnea events in non-snoring children]

Objective: To investigate the characteristics of sleep-related respiratory events in normal children and to provide normal polysomnographic parameters for diagnosing sleep-disordered breathing in children. Methods: Normal subjects between 3 and 14 years old were enrolled from 1 July 2014 to 31 December 2015 and the subjects received overnight polysomnography at the sleep center of our hospital. They were children of our hospital employees or were recruited from the communities who did not have sleep and respiratory disorders. The children were divided into preschool group (3-5 years) and school-age group (6-14 years). Apnea index (AI), obstructive apnea index (OAI), central apnea index (CAI), and mixed apnea index (MAI) were compared between the two groups. Data for continuous variables that showed normal distribution were expressed as x ±s. M(P₂₅, P₇₅) were used when data were not normally distributed. Continuous variables that showed normal distribution were compared by using an independent-sample t-test. Wilcoxon-test was performed when data exhibited non-normal distribution. Differences in categorical data were tested with Chi-square test. Pearson correlation test was applied for the correlation analysis. P<0.05 was considered statistically significant. Results: A total of 115 normal children took part in the study including 40 in preschool group and 75 in school-age group. Children in both groups had a few sleep apnea events, most of which were central apneas, accounting for 80% and 70% of the total respiratory events respectively. Central apnea index in preschool children were significantly higher than that of school-age children (P<0.001), with median of 0.6 times/h and 0.1 times/h, respectively. Median OAI of both groups were 0.0 times/h without significant difference (P=0.748). Obstructive apnea events occurred mainly in the supine position in both groups. Conclusions: Normal children may have a few apnea events in sleep that were predominantly central apnea. CAI of preschool children is significantly higher than that of school-age children. Obstructive sleep apnea is rare in normal children, and sleep apnea occurs mainly in the supine position.