Abstract              Forty one patients with obstructive sleep apnoea had neuropsychologic testing prior to nocturnal sleep study in a sleep disorders clinic. The patients who had obstructive sleep apnoea with hypoxemia had more severe cognitive impairment than normal control subjects. Obstructive sleep apnoea had significantly poorer cognitive functioning on four of eight tests (p<0.005) In addition, the patients who had obstructive sleep apnoea had mean performance scores in the impaired range on measures of attention, concentration, complex problem-solving, and short-term recall of verbal and spatial information. In contrast, the normal healthy subjects had no mean performance score in the impaired range. The degree obstructive sleep apnoea during sleep and wakefulness significantly correlated with the degree of overall cognitive impairment t; however, measures of sleep fragmentation did not significantly correlate with overall cognitive impairment in patients with obstructive sleep apnoea. We conclude that patients who have obstructive sleep apnoea have cognitive impairment which is more severe than those normal healthy subjects.

Key Words: Obstructive sleep apnea; cognitive impairment; Mini mental scale.