Correlation between sleep and cognitive functions after hemispheric ischaemic stroke

Background: The aim of this study was to test the hypothesis of a link between sleep and cognitive functions, particularly memory and attention, after stroke. Methods: We studied 11 consecutive patients with first-ever hemispheric ischaemic stroke within eight days after symptoms onset and nine of them at least three months after stroke. Sleep EEG was recorded with a portable system. Cognitive functions were assessed using a standardized battery of tests allowing the estimation of the most relevant domains of cognition. Five age-matched healthy subjects served as controls. Results: The patients were aged 43 +/- 12 years (18-59). In five patients stroke was right-sided and in six patients left-sided. In the acute stroke phase a correlation between attention and amounts of slow wave sleep (SWS), Rapid eye movement (REM) sleep and sleep efficiency was found. In the recovery phase verbal/figural memory and attention significantly improved in most patients. Furthermore, an association between (i) verbal/figural (non-verbal) memory and amounts of SWS, REM sleep and sleep effciency, and between (ii) attention and sleep effciency was observed. Conclusions: The results point to a link between sleep and cognitive functions and their recovery after hemispheric stroke. Further studies are needed to determine the specific nature of this link.