Sleep in Down Syndrome

Abstract

Down Syndrome (DS), caused by an extra copy of chromosome 21 (Trisomy 21), is the single most common genetic condition in humans, with an incidence of 1 in 800 births (approx 350 live births annually in Australia). Although variable in severity, symptoms of DS include hypotonia, craniofacial abnormalities, and cognitive deficits. These symptoms lead to a delay in reaching the developmental milestones of childhood and to varying degrees of intellectual disability. As is common in intellectual disability, sleep in DS has been shown to be highly fragmented. Frequent arousals and awakenings are partially related to the increased prevalence of sleep disordered breathing in this group. Obstructive sleep apnea (OSA) has been reported to occur in up to 60% of children with DS compared with 1-3% in the general paediatric population. A number of predisposing factors place individuals with DS at greater risk for developing OSA. Craniofacial abnormalities such as mid-face and mandibular hypoplasia, a small upper airway with relatively large and medially positioned tonsils, and relative macroglossia all contribute to airway obstruction during sleep. In addition, obesity and generalised hypotonia also contribute to collapse of the upper airway during sleep. Although there are few studies evaluating sleep in adults with DS, they all indicate that the high prevalence of OSA in this group continues through adulthood and is strongly associated with obesity. Individuals with DS also have reduced cardiorespiratory responsiveness, including a reduced heart rate response to arousal from sleep, and dampened sympathetic outflow which may pose unique complications in the setting of OSA. As the negative consequences of sleep disruption and OSA are similar to the inherent features of DS, the significant contributions of disturbed sleep in this group may be overlooked until formal investigation. However, just as in the non-DS individual, detection of sleep disorders may be critical to minimise long-term cardiovascular consequences and also maximise the intellectual potential of the person with DS.