Sleep quality and clinical correlates in patients on maintenance dialysis

Background: Sleep quality is a subject of increasing interest to clinicians caring for dialysis patients. Self-assessed sleep disturbances have been associated with quality of life outcomes. The goal of this study was to identify clinical and laboratory parameters that are independently associated with overall sleep quality among prevalent dialysis patients. Methods: The Epworth Sleepiness Scale (ESS) and the Sleep Problems Index (SPI), a questionnaire derived from the Medical Outcomes Study, were administered to 71 dialysis patients and 68 subjects without known kidney disease (control group). The ESS and the SPI sleep item responses between the 2 groups were compared. The sleep items from the SPI were also aggregated into a sleep quality score. Multivariate linear regression analyses of sleep quality scores were used to identify clinical factors that were independently associated with poor sleep. Results: The ESS score was not significantly different between the 2 groups. However, the responses to the SPI sleep items demonstrated significantly impaired subjective sleep quality in dialysis patients compared with control subjects. In addition, overall sleep quality, as measured by the aggregated sleep score, was lower in dialysis patients compared with the control group (41 vs. 47, p < 0.001). In multivariate analyses, factors that were independently associated with poor sleep quality in dialysis patients were male gender (p = 0.006), history of coronary artery disease (p = 0.003), and high phosphate level (p = 0.05). Conclusion: This study demonstrates that global sleep quality of dialysis patients is substantially impaired. Poor sleep quality was associated with male gender, coronary artery disease and high serum phosphate level, a modifiable factor. Future studies are needed to examine the relationship of serum phosphate level to sleep quality in dialysis patients.