Sleep Disturbance, Cognition, and Behavior in Down Syndrome

Abstract

Children and adolescents with Down Syndrome (DS) have a high incidence of sleep problems, including Obstructive Sleep Apnea Syndrome (OSAS). They are also likely to have deficits in neuropsychological tasks tapping prefrontal function and hippocampal function. There has recent revival of literature suggesting an active role for sleep in memory consolidation and problem-solving in both children and adults. Furthermore, given the cognitive and behavioral sequellae of OSAS in typically developing children it is logical to test if the hypoxemia and increased sleep fragmentation, the two major pathophysiological mechanisms of OSAS, seen in children with DS and OSAS may exacerbate learning or behavior disorders.Forty children with DS aged 7-18 were administered the Arizona Cognitive Test Battery (ACTB) for DS (Edgin et al., 2010), and in-home ambulatory polysomnography. Their parents were asked to complete several questionnaires assessing their child's sleep and behavior. Seventy-seven percent (n = 40) of our sample met criteria for pediatric sleep apnea (AHI>1.5), and the mean apnea hypoppnea index (AHI) was 8.4 events per hour. Our sample had a mean arousal index of 10.3, a respiratory arousal index of 3.2, and a SaO2 nadir of 86.9%. Over 70% of our sample had a SaO2 nadir below 90%. We examined the relationship between OSAS severity and cognitive and behavioral outcomes. We found that children with DS with a lower apnea hypopnea index (AHI) attained a greater number of stages on the CANTAB PAL task compared to chronologically age-matched children with higher AHI, and the variance in performance was partially explained by sleep fragmentation (i.e., the arousal index) and experimenter-rated "attention" but not hypoxemia. In addition, we also found that the low apnea group showed a trend toward outperforming the high apnea group on the KBIT-II Verbal IQ scale and DAS-2 Pattern Construction subtest.These findings have important clinical implications. First, these results suggest that early screening for OSAS in DS is important, as OSAS severity seems to explain some of the variance in cognitive functioning. Second, these findings suggest that an early intervention for OSAS might be warranted.