Down syndrome (DS) is the most common neurodevelopmental disorder of known genetic cause, with an incidence of between 1:750 and 1:1000 live births. There is an increased risk of sleep fragmentation in DS because of obstructive sleep apnea in this population. This study found that, even in the euploid population, poor sleep quality, particularly sleep fragmentation, is a strong predictor of poor executive function. This Recommendation is of an article referenced in an F1000 Faculty Review also written by Annette Karmiloff-Smith.