Factors associated with severity of sleep apnoea syndrome in patients with chronic kidney disease

Background In patients with chronic kidney disease (CKD), prevalence of sleep apnoea syndrome (SAS) is reported to be markedly high. However, the factors associated with severity of SAS in such patients rarely have been reported. Methods This was a cross-sectional study of 100 stable non-dialysis patients with CKD who attended a CKD educational programme from April 2014 to August 2015. Diagnosis of SAS and its severity were assessed using a type-3 portable monitor. Results Eighty-six men and 14 women with a mean age of 71.6 ± 9.7 years were included. Mean apnoea-hypopnoea index (AHI) was 26.0 ± 13.8. Severe SAS was seen in 39 patients. Significant differences in brain natriuretic peptide (BNP) level (213.6 ± 329.6 pg/mL vs 107.8 ± 141.3 pg/mL, P < 0.05) and cardiothoracic ratio (CTR, 52.4% ± 6.3% vs 49.6% ± 5.7%, P < 0.05) were seen between patients with and without severe SAS. After adjusting for various parameters, BNP level, CTR, and diameter of the inferior vena cava at the end of inhalation were found to correlate with AHI. Conclusions In patients with CKD, prevalence of severe SAS is extremely high. In these patients, fluid retention, rather than systolic or diastolic function, correlates with severity of SAS.