Effect of Prolonged Weekly Hemodialysis on Survival of Maintenance Hemodialysis Patients: A Meta-Analysis of Studies

Objective: Use of prolonged nocturnal or daytime hemodialysis (PHD, more than 12 h per week) is associated with improvement of some clinical parameters relative to conventional hemodialysis (CHD, 4 h sessions, thrice weekly), but the effect on survival is unclear. The purpose of this meta-analysis is to determine whether PHD improves survival of patients undergoing maintenance HD. Design: Systematic review of observational studies by meta-analysis. Data Sources: Electronic searches in MEDLINE (PubMed, 1966-2012), EMBASE (1974-2012), www.clinicaltrials.gov, and the Cochrane Controlled Clinical Trials Register Database. Eligibility Criteria for Selecting Studies: All prospective or retrospective studies were considered eligible if they were cohort studies or observational studies that compared CHD with PHD (more than 12 h of HD per week due to more HD sessions or increased duration of HD sessions) and the final outcome was all-cause death or mortality. Results: Thirteen studies with a total of 85,722 participants (10,285 PHD patients, 75,437 CHD patients) met the inclusion criteria. Summary estimates indicated that PHD was associated with decreased risk of mortality (OR = 0.72, 95% CI 0.64-0.81, p < 0.00001). Analysis of residual confounders of pooled results from six retrospective studies indicated that PHD patients were less likely to have low hemoglobin (11.7 vs. 11.2 g/dl, p < 0.01), younger (51.2 vs. 58.8 years, p < 0.01), less likely to have diabetes (27.1 vs. 40.8%, p < 0.01), and less likely to use a catheter (18.4 vs. 27.1%, p < 0.01), so these may have affected the outcome measure in these studies. Conclusions: PHD is associated with improved survival relative to CHD, although residual confounders have affected this relationship in observational studies. Large, multicenter randomized, controlled trials are needed to confirm our results.