Association of Sleep-Disordered Breathing With Cognitive Dysfunction in CKD Stages 4-5

Background: Sleep-disordered breathing and cognitive impairment are common in patients with chronic kidney disease (CKD). Sleep-disordered breathing is known to be a risk factor for cognitive dysfunction in the general population, but this association has not been studied in patients with CKD. Study Design: Cross-sectional study. Settings & Participants: A cohort of 169 patients with CKD stages 4-5. Predictors: Sleep-disordered breathing; covariates included demographics, diabetes, cardiovascular disease, depression, and dialysis modality. Outcomes: Cognitive impairment, generally defined as a score 1.5 standard deviations or more from the age-and education level-adjusted normative cognitive test score. Measurements: Standardized health interview, neurocognitive assessment, sleep-related questionnaires, and polysomnography. Results: Sleep-disordered breathing (apnea-hypopnea index > 15) was diagnosed in 83 (49.1%) individuals. This group had a significantly higher prevalence of nocturnal hypoxemia (65.8% vs 26.8%; P < 0.001) and excessive daytime sleepiness (38.6% vs 20.7%; P = 0.01). In addition, this group had significantly lower scores in tests measuring verbal memory, working memory, attention, and psychomotor speed. Sleep-disordered breathing was associated with higher risk of immediate verbal memory impairment after adjustment for known confounders (adjusted OR, 2.67; 95% CI, 1.17-6.08). However, in a subgroup analysis of older adults (aged > 60 years), there were no significant differences in cognitive testing between the groups with and without sleep-disordered breathing. Limitations: Cross-sectional design, limited sample size. Conclusions: Sleep-disordered breathing is associated with cognitive impairments, especially impaired verbal memory, in patients with advanced CKD. However, the impact appeared limited in older adults. Early evaluation and management of sleep-disordered breathing in patients with CKD may provide an opportunity to improve cognitive function. Am J Kidney Dis. 60(6): 949-958. (C) 2012 by the National Kidney Foundation, Inc.