Survival by time of day of hemodialysis: analysis of United States Renal Data System Dialysis Morbidity and Mortality Waves III/IV.

BACKGROUND: Whether morning shift hemodialysis is associated with improved survival in comparison to patients receiving afternoon shift hemodialysis has not been shown for a representative sample of US chronic hemodialysis patients.
METHODS: We conducted a historical cohort study of a national database (US Renal Data System Dialysis Morbidity and Mortality Waves III/IV) of 6,939 patients who started hemodialysis therapy from January 1, 1990, through December 31, 1993. Patients were followed up through April 9, 2000, and censored at the time of change to a different modality, including transplantation. We estimated the adjusted hazard ratio for all-cause mortality based on the time of day of hemodialysis (0500 to 1200 for morning shift, 1200 to 1800 for afternoon shift, 1800 to midnight for evening shift). Cox regression analysis was used to adjust for other factors associated with survival.
RESULTS: For patients aged 60 years and older, the unadjusted 4-year survival rate for patients on morning shift hemodialysis was 28.8% versus 24.1% for patients on afternoon shift hemodialysis and 38.7% for patients on evening shift hemodialysis (P < 0.01 by log-rank test for both versus afternoon shift hemodialysis). Both morning shift (adjusted hazard ratio, 0.90; 95% confidence interval [CI], 0.83 to 0.98; P = 0.02) and evening shift hemodialysis (adjusted hazard ratio, 0.62; 95% CI, 0.48 to 0.80; P < or = 0.001) were independently associated with a lower risk for mortality compared with afternoon shift hemodialysis. No such differences were seen for patients younger than 60 years. Both morning shift and evening shift hemodialysis were independently associated with improved survival compared with afternoon shift hemodialysis in elderly chronic hemodialysis patients. No such association was found for younger patients.