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.