Although a broad range of neuropsychological deficits have been reported to occur in patients with Obstructive Sleep Apnea Syndrome (OSAS), few studies have examined the executive functions in this patient group. The executive functions provide conscious control of the more basic cognitive functions and play an important role in daily living. They include capacities such as concept formation, planning, cognitive flexibility and resistance to interference. This study compared the performance of groups of moderate and severe OSAS patients with a group of unaffected individuals (N=24), on five tests of executive functioning. Two indices of sleep disordered breathing, sleep fragmentation and . hypoxemia, obtained from overnight polysomnography, were respectively used to categorise participants. ID patients with severe OSAS, executive function deficits were evident, while in those with moderate OSAS these abilities appeared largely intact. Further analyses revealed that the observed findings could not be attributed to differences in vigilance. These results suggest a discontinuity in the manifestation of executive function deficits between moderate and severe OSAS patients. There may be a threshold of OSAS severity, which if exceeded, impairments tend to occur. The magnitude of the impairment in patients with severe OSAS may be sufficient to interfere with daily cognitive functioning. Further research is needed both to replicate these findings and to establish the underlying pathogenesis of these deficits.

Thesis (M.A.)-University of Natal, Pietermaritzburg, 2001.