NEUROPSYCHOLOGICAL FUNCTION IN MILD SLEEP-DISORDERED BREATHING

Although a broad range of neuropsychological deficits has been reporte d in patients with severe sleep disordered breathing (SDB), little is known about the impact of mild SDB on neuropsychological performance. In this study, we compared neuropsychological test performance in two groups of carefully screened volunteers who differed clearly according to the respiratory disturbance index (RDI). Controls (n = 20) were id entified on the basis of an RDI < 5: cases (n = 32) had an RDI in the range of 10-30. Cases and controls were well matched with regard to IQ , age, and sex. Cases had significantly more self-reported snorting an d apneas and a higher body mass index than controls but did not differ according to sleepiness as measured by either the multiple sleep late ncy test or the Epworth sleepiness scale. An extensive battery of neur opsychological and performance tests was administered after an overnig ht sleep study. Cases performed significantly more poorly on a visual vigilance task (perceptual sensitivity, d':2.24 +/- 0.64 vs. 2.70 +/- 0.53, p = 0.01, for cases and controls, respectively) and a. test of w orking memory, the Wechsler adult intelligence scale-revised digits ba ckwards test (6.12 +/- 2.20 vs. 7.55 +/- 2.22, p = 0.02), than control s. The groups did not differ in their performance on other tests of me mory. information processing. and executive functioning. In summary, s ubjects with mild SDB may manifest a vigilance deficit in the absence of substantial sleepiness. subjects with a mildly elevated RDI (10-30) without sleepiness do not appear to suffer appreciable deficits in mo re complex neuropsychological processes (e.g. executive functions).