Effect of comorbidity on the increased mortality associated with early initiation of dialysis

Background: Current recommendations for initiating dialysis therapy are based on level of kidney function and clinical evidence of uremia. Several studies reported no benefit in patient survival from initiating dialysis therapy with a greater glomerular filtration rate (GFR). Whether this is explained by a greater comorbidity burden or detrimental effect of early initiation remains unclear. We thus undertook an evaluation of the impact of comorbidity on the association between GFR at initiation and death. Methods: Data from the Center for Medicare & Medicaid Services were used to derive 3 incident dialysis populations: (1) general population aged 18+ years, (2) older patients aged 67+ years, and (3) a "low-risk" subgroup without diabetes, heart failure, or atherosclerotic heart disease. A Cox proportional hazard regression technique was used. Results: Greater GFR at initiation of dialysis therapy was associated with a greater risk for death in all populations, and sequential adjustment for additional covariates attenuated the effect. Patients in the general dialysis population who initiated dialysis therapy at a GFR greater than 10 mL/min/1.73 m² (>0.17 mL/s) had a 42% increased risk for death compared with patients with a GFR less than 5 mL/min/1.73 m² (<0.08 mL/s) at initiation of dialysis therapy after adjusting for all covariates. In the older and healthier populations, adjusted increased risks were 25% and 39%, respectively. Conclusion: Patients initiating dialysis therapy at greater GFRs have an increased risk for death not fully explained by comorbidity. Additional research is required to determine the reasons for poor survival in patients who start dialysis therapy with significant residual renal function.