GFR decline and mortality risk among patients with chronic kidney disease

Abstract

Background and objectives: Estimates of the effect of estimated GFR (eGFR) decline on mortality have focused on populations with normal kidney function, or have included limited information on factors previously shown to influence the risk of death among patients with CKD.

Design, setting, participants, & measurements: We retrospectively assessed the effect of rate of eGFR decline on survival of patients with CKD receiving primary care through a large integrated health care system in central Pennsylvania between January 1, 2004, and December 31, 2009.

Results: A total of 15,465 patients were followed for a median of 3.4 years. Median rates of eGFR change by those in the lower, middle, and upper tertiles of eGFR slope were -4.8, -0.6, and 3.5 ml/min per 1.73 m(2)/yr, respectively. In Cox proportional hazard modeling for time to death, adjusted for baseline proteinuria, changes in nutritional parameters, and episodes of acute kidney injury during follow-up (among other covariates), the hazard ratio for those in the lower (declining) and upper (increasing) eGFR tertiles (relative to the middle, or stable, tertile) was 1.84 and 1.42, respectively. Longitudinal changes in nutritional status as well as episodes of acute kidney injury attenuated the risk only modestly. These findings were consistent across subgroups.

Conclusions: eGFR change over time adds prognostic information to traditional mortality risk predictors among patients with CKD. The utility of incorporating eGFR trends into patient-risk assessment should be further investigated.

Figure 1.

Cohort development. CA-AKI, community-associated acute kidney injury; eGFR, estimated GFR; HA-AKI, hospital-associated acute kidney injury; NDD-CKD, non–dialysis-dependent chronic kidney disease.

Figure 2.

Risk of death among subgroups of patients with baseline nondialysis dependent CKD, by tertile of eGFR change over time. For the BMI/ALB subgroup analysis, patients with both BMI and serum albumin results (or with either one alone if the other was not assessed in follow-up) at the time of last follow-up equal to or greater than the baseline value were classified as nutritionally stable; those with one or both values less than baseline value were classified as “malnourished.” 439 (2.8%) patients had no follow-up BMI or serum albumin; these patients were not included in the analysis of nutritional change. ALB, serum albumin; BMI, body mass index; decl, declining GFR group; incr, increasing GFR group; neg, negative; pos, positive.

Figure 3.

Functional point estimate (and 95% pointwise confidence band) between estimated GFR change and the hazard ratio for death among patients with non–dialysis-dependent chronic kidney disease, estimated by a restricted cubic spline function. Adjusted model includes age, gender, race, smoking history, hypertension, heart failure, peripheral vascular disease, hypertension, Charlson Comorbidity Index score, and dementia present at the time of cohort entry; a prescription for beta blocker, loop diuretic, aldosterone antagonist, calcium acetate, insulin, coumadin, or aspirin at time of cohort entry; systolic and diastolic BP, proteinuria, HDL and LDL cholesterol levels, estimated GFR at time of cohort entry, hospital- and community-associated acute kidney injury during follow-up, change in body mass index during follow-up, and baseline serum albumin. Bold lines represent point estimates; faint lines represent 95% confidence bands.