Sleep pressure score: a new index of sleep disruption in snoring children

Study Objectives: Excessive daytime sleepiness (EDS), as measured by objective criteria, is infrequent in snoring children despite a high prevalence of EDS-related behavioral manifestations. We hypothesized that sleep architecture and arousal indexes may be altered relative to the severity of sleep-disordered breathing (SDB). Design: Retrospective and prospective study. Setting: Questionnaires were distributed through sleep clinic or school program; polysomnograms were performed at Kosair Children's Hospital in Louisville, Kentucky. Participants: To examine this issue, 182 children with SDB, 163 children with primary snoring, and 214 control children with a mean age of 6.9 +/- 2.6 years underwent polysomnographic evaluation in the laboratory. Measurements and Results: Significant increases in slow-wave sleep (percentage of total sleep time) and decreases in rapid eye movement sleep (percentage of total sleep time) occurred in the SDB group (P < .0001). Spontaneous and respiratory arousal indexes and the apnea-hypopnea index (AHI) displayed negative and positive correlations, respectively, suggesting reciprocal interactions. Based on these observations, a sleep pressure score (SPS) was derived as a surrogate numeric measure for disrupted sleep homeostasis. The SPS exhibited linear increases relative to AHI, reaching a plateau at an AHI of 30 to 40 per hour of total sleep time. Furthermore, SPS values were significantly higher among African American and obese children (P < .0001). Conclusions: Sleep architecture is not preserved in children with SDB. An algorithm allowing for calculation of sleep propensity and disturbed sleep homeostasis in children who snore is proposed and may be of practical value in the assessment of sleepiness.