Intermittent hypoxia and long-term neurological outcome: How are they related?

This review looks at data on potential associations between intermittent hypoxia (IH) and impaired neurodevelopment in infants and children. In extremely preterm infants (< 28 wk gestation), such an association has been established based on a secondary analysis of Canadian Oxygen Trial data. These showed, in 997 infants, that the odds of developing cognitive or language impairment at 18 months corrected age were 3 times higher in infants who were in the highest decile for %time spent with events where pulse oximeter saturation (SpO(2)) was < 80% for >1 min during their first 10 postnatal weeks compared to those who had very few such events after birth. In older term and preterm infants, the occurrence of 5 or more events with prolonged apnea and bradycardia during home monitoring was associated with 5 points less on the mental development index of the Bayley-II scales. For older children, associations between sleep-disordered breathing and impaired cognition/academic achievements have also been established, but not consistently, and it remains unclear whether this association is primarily mediated via IH or via sleep deprivation. Animal data show that IH may cause apoptosis particularly in the hippocampus. Although we need to stress that associations cannot prove causality, current evidence provides support for IH to be detected and prevented early. Future studies should focus on IH rather than on apnea/bradycardia.