Association between sleep-disordered breathing and neuropsychological performance in older adults with mild cognitive impairment

Sleep-disordered breathing in middle-age and older adults has been shown to be linked to a range of neuropsychological deficits, but the extent to which these relationships are evident in older people 'at risk' of developing dementia in unknown. In this study, we aimed to determine whether changes in sleep-disordered breathing and sleep fragmentation during nocturnal sleep were related to neuropsychological dysfunction in patients with mild cognitive impairment. Forty-six patients with MCI (mean age = 66.1 y, sd = 8.4) and 40 age-matched healthy controls (mean age = 63.5 y, sd = 8.9) underwent psychiatric, medical, and neuropsychological assessment, in addition to overnight polysomnography and self-report questionnaires. Measures of hypoxemia, sleep fragmentation, and sleep quality were derived including the apnoea-hypopnea index, oxygen desaturation index, percentage of total sleep time spent below 90% oxygen saturation, arousal index, sleep efficiency, and wake after sleep onset. Patients with MCI did not differ from healthy aging on any measure of sleep-disordered breathing or sleep fragmentation. In MCI, processing speed was negatively correlated with greater sleep time spent below 90% oxygen saturation and a higher apnoea-hypopnea index. In contrast, in the healthy aging, processing speed was negatively correlated with an increased oxygen desaturation index and the arousal index. Sleep-disordered breathing is evident in both healthy aging and MCI with associated decrements in processing speed. Future research is needed to determine the unique and synergistic effects of these differential associations, their potential to inform disease trajectory, and possible therapeutic interventions.