Poor sleep is a common feature in autism even though patients themselves do not necessarily complain. The impact of poor sleep on daytime cognitive functioning in autism is not well-known and we therefore investigated whether sleep in autism correlates with daytime cognitive performance. A battery of non-verbal tasks was administered, in the morning after a second night of sleep in the laboratory, to 17 young adults with autism and normal intelligence, and 14 typically developed individuals matched for age and IQ; none of the participants complained about sleep problems. Two dimensions of attention (sustained and selective) and 4 types of memory (working, declarative, sensory-motor and cognitive procedural) were tested. Individuals with autism showed clear signs of poor sleep. Their performance differed from the controls in response speed but not in accuracy. Signs of poor sleep in the autism group were significantly correlated with either normal performance (selective attention and declarative memory) or performance inferior to that of the controls (sensory-motor and cognitive procedural memories). Both groups presented a significant negative correlation between slow-wave sleep (SWS) and learning a sensory-motor procedural memory task. Only control participants showed a positive association between SWS duration and number of figures recalled on the declarative memory task. Correlation patterns differed between groups when sleep spindles were considered: they were negatively associated with number of trials needed to learn the sensory-motor procedural memory task in autism and with reaction time and number of errors on selective attention in the controls. Correlation between rapid eye movements (REMs) in REM sleep and cognitive procedural memory was not significant. We conclude that some signs reflecting the presence of poor sleep in adults with high-functioning autism correlate with various aspects of motor output on non-verbal performance tasks. The question is raised whether poor sleep in non-complaining persons with autism should be treated.
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