A review of executive functions in obstructive sleep apnea syndrome

Objectives - To provide an update on recent research concerning obstructive sleep apnea syndrome (OSAS) and executive functions. Methods - A systematic review was carried out on reports drawn from MEDLINE and PSYCHLIT (January 1990 - December 2005) and identified from lists of references in these reports. The selection criteria were met by 40 articles. Results - The sample sizes in the reviewed studies varied widely and consisted mostly of selected groups. Most patient samples were heterogeneous in terms of the severity of OSAS. Executive functions were generally assessed with standardized test methods. Half of the studies assessed executive functions using only one or two tests. The most defected domains of executive functions were working memory, phonological frequency, cognitive flexibility, and planning. Continuous positive airway pressure ( CPAP) treatment improved performance times, cognitive flexibility, and planning. Deficits in working memory and phonological frequency persisted. Conclusions - Executive functions are the most defected cognitive domain in OSAS. Previous studies are affected by the heterogeneity of patient samples and the definitions of the domains of executive functions. Executive functions in OSAS should be assessed with a standardized neuropsychological test battery including assessments of different domains of executive functions. More research is needed on the efficiency of CPAP treatment on executive dysfunctions.