Movement Distribution: A New Measure of Sleep Fragmentation in Children with Upper Airway Obstruction

Study Objectives: To develop a measure of sleep fragmentation in children with upper airway obstruction based on survival curve analysis of sleep continuity. Design: Prospective repeated measures. Setting: Hospital sleep laboratory. Participants: 92 children aged 3.0 to 12.9 years undergoing 2 overnight polysomnographic (PSG) sleep studies, 6 months apart. Subjects were divided into 3 groups based on their obstructive apnea and hypopnea index (OAHI) and other upper airway obstruction (UAO) symptoms: primary snorers (PS; n = 24, OAHI < 1), those with obstructive sleep apnea syndrome (OSAS; n = 20, OAHI >= 1) and non-snoring controls (C; n = 48, OAHI < 1). Interventions: Subjects in the PS and OSAS groups underwent tonsillectomy and adenoidectomy between PSG assessments. Measurements and Results: Post hoc measures of movement and contiguous sleep epochs were exported and analyzed using Kaplan-Meier estimates of survival to generate survival curves for the 3 groups. Statistically significant differences were found between these group curves for sleep continuity (P < 0.05) when using movement events as the sleep fragmenting event, but not if stage 1 NREM sleep or awakenings were used. Conclusion: Using conventional indices of sleep fragmentation in survival curve analysis of sleep continuity does not provide a useful measure of sleep fragmentation in children with upper airway obstruction. However, when sleep continuity is defined as the time between gross body movements, a potentially useful clinical measure is produced.