Sleep fragmentation and hypoxaemia as key indicators of cognitive impairment in patients with obstructive sleep apnoea

Abstract

This study aimed to identify characteristics associated with cognitive impairment in older individuals with obstructive sleep apnoea (OSA) using the Addenbrooke’s Cognitive Examination-Revised (ACE-R) that could aid in stratifying those at higher risk for impairment. We analysed existing cross-sectional datasets that measured the performance of 89 adult patients (aged 50–85 years) with OSA on the ACE-R cognitive test. Receiver operating characteristic curves and logistic regression analysis were utilised to identify associations between impairment status and various factors, including demographic characteristics, self-reported sleepiness, cognitive complaints, and OSA severity. According to established thresholds (ACE-R ≤ 88), 36% of participants were cognitively impaired. When adjusted for age and education, the strongest factors associated with impairment status were prior measures of arousal index (cut-off: ≥28events/hr, OR: 5.67, p < 0.01), sleep mean SpO2 (cut-off: ≤92%, OR: 3.52, p < 0.05), 3% oxygen desaturation index (cut-off: ≥27events/hr, OR: 3.75, p < 0.05), and sleep time spent under 90% SpO2 (cut-off: ≥9%, OR: 3.16, p < 0.05). Combining these factors achieved a high sensitivity (≥ 93%) of detecting impairment within this cohort. Conversely, the apnoea-hypopnoea index, daytime sleepiness, and cognitive complaints were not associated with impairment status. The ACE-R identified a significant proportion of patients with OSA as having cognitive impairment. Traditional indices of sleep fragmentation and hypoxaemia may allow clinicians to identify at-risk patients for cognitive evaluation, however further studies are needed to validate these findings and explore whether poor cognitive performance can be remediated via OSA treatment.