Polysomnography
Participants underwent overnight in-laboratory polysomnography at the Johns Hopkins Pediatric Sleep Center. Polysomnography was performed according to standard American Academy of Sleep Medicine (AASM) guidelines16,17. Parameters monitored included electroencephalogram, electrooculogram, submental and pretibial electromyogram, electrocardiogram, nasal airflow monitored with a pressure transducer and thermistor, thoracic and abdominal plethysmography, end-tidal CO2 and pulse oximetry.
Scoring of the polysomnography was performed by a trained sleep technician and reviewed by a pediatric sleep physician (LS). An obstructive apnea was defined by the absence of airflow in the nasal and oronasal airflow with ongoing respiratory effort for at least two breath cycles. An obstructive hypopnea was defined as a drop-in airflow (> 30% of baseline) with ongoing respiratory effort for at least two breath cycles terminated by an arousal from sleep or a ≥ 3% fall in oxyhemoglobin saturation. OSA was defined as an obstructive apnea‐hypopnea-index (AHI) of ≥2 events per hr.