Sleep-disordered breathing (SDB) and neuropsychological function: A community sample study

Abstract

This is a case-control study investigating the relationship of sleep-disordered breathing (SDB) to neuropsychological functioning. Participants were recruited from the Tucson Sleep Heart Health Study (SHHS), which is a population-based study examining cardiovascular consequences of SDB. A sample of 103 men and women, ages 40-75, consisting of 51 controls (CTL group) and 52 persons with SDB (SDB group), matched by age (± 5 years) and sex, was enrolled. CTL subjects had a respiratory disturbance index (RDI), a measure of SDB, ≤ 5 while the SDB subjects had a RDI 20 to 50, inclusive. All participants had an overnight in-home polysomnography (PSG) prior to undergoing a neuropsychological evaluation. Psychological functioning was assessed and the areas of cognitive functioning that were tested included general intelligence, attention and working memory, psycho-visuo-motor efficiency, manual dexterity, and frontal/executive function. The SDB group performed significantly worse on the Stroop Color-Word test, made more errors on the Controlled Oral Word Association test, and overestimated time elapsed. The SDB group also demonstrated a statistical trend ( p ≤ 0.10) for worse performance on Wechsler Adult Intelligence Scale - III Digit Span, Letter-Number Sequencing and Digit Symbol Coding subtests, and the non-dominant hand performance on the Grooved Pegboard. Factor analyses were performed to reduce the number of neuropsychological variables and measures of SDB. Controlling for IQ, multiple regression analyses showed a significant negative association between a "nocturnal hypoxemia" factor and both "manual dexterity" and "semantic memory" factors. The results suggest that persons with moderate SDB, compared to controls, did not report increased depression or other aspects of psychological distress. SDB is, however, associated with subtle neuropsychological decrements in frontal/executive function, psycho-visuo-motor efficiency, and working memory. The performance decrement in tasks of frontal executive function and manual dexterity was primarily associated with nocturnal hypoxemia and not to the frequency of sleep fragmentation.