Introduction: Children with congenital heart disease (CHD) are at increased risk for neurocognitive impairment. Prior research has shown an increased risk of obstructive sleep apnea (OSA) in children with CHD. Given that OSA is a known cause of neurocognitive impairment in children without CHD, we hypothesized that OSA may contribute to the observed neurocognitive impairment in children with CHD. Methods: Children age 6-17 years of age with surgically corrected moderate-complex CHD without comorbid neurodevelopmental syndrome (such as Down syndrome or DiGeorge syndrome), prematurity, current cyanosis or history of seizures were recruited from the pediatric cardiology clinic. Participants underwent home sleep testing (Resmed ApneaLink Air) and IQ testing (Kaufman Brief Intelligence Test). Children with an obstructive apnea-hypopnea index >1 were considered to have OSA. Medical records were reviewed to abstract CHD surgical history. Linear regression was performed to identify potential risk factors for neurocognitive impairment. Potential risk factors examined included OSA, age at first cardiac surgery, history of cyanotic CHD, CHD severity (Bethesda criteria), number of cardiac surgeries and Fontan circulation as possible covariates. Results: Out of 30 total children, eighteen children (60%) were found to have OSA. Twenty one children had cyanotic CHD (70% with OSA) and nine children had non-cyanotic CHD (50% with OSA, p=0.70). Fifteen children had complex CHD (60% with OSA) and 15 children had moderate CHD (60% with OSA, p=1.0). There was no association between cyanotic CHD or CHD severity and presence of OSA. Among CHD-related factors, only history of cyanotic CHD was a significant predictor of total IQ (β=-14, p=0.005). We found that the presence of OSA was associated with an 11 point decrease in total IQ after adjustment for history of cyanotic CHD (p=0.01). Additionally, there was no interaction between cyanotic CHD and OSA (p=0.61). Conclusions: OSA appears to be a highly prevalent significant independent risk factor for neurocognitive impairment in children with CHD. Given that OSA is typically amenable to treatment, OSA may be a reversible cause of neurocognitive impairment in children with CHD. [ABSTRACT FROM AUTHOR]