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. 2024 Aug 22;17(11):sfae254.
doi: 10.1093/ckj/sfae254. eCollection 2024 Nov.

Longitudinal serum bicarbonate and mortality risk in older patients with advanced chronic kidney disease: analyses from the EQUAL cohort

Gianmarco Lombardi  1 , Nicholas C Chesnaye  2   3 , Fergus J Caskey  4 , Friedo W Dekker  5 , Marie Evans  6 , Olof Heimburger  6 , Maria Pippias  4   7 , Claudia Torino  8 , Maciej Szymczak  9 , Christiane Drechsler  10 , Christoph Wanner  10 , Giovanni Gambaro  1 , Vianda S Stel  2   3 , Kitty J Jager  2   3 , Pietro Manuel Ferraro  1 ; EQUAL study investigators
Collaborators, Affiliations

Longitudinal serum bicarbonate and mortality risk in older patients with advanced chronic kidney disease: analyses from the EQUAL cohort

Gianmarco Lombardi et al. Clin Kidney J. .

Abstract

Background: We aimed to explore the relationship between serum bicarbonate (SBC) and mortality in advanced chronic kidney disease (CKD) during three distinct treatment periods: during the pre-kidney replacement therapy (KRT) period, during the transition phase surrounding the start of KRT (transition-CKD) and during KRT.

Methods: Using the European QUALity Study on treatment in advanced CKD (EQUAL) cohort, which includes patients aged ≥65 years and estimated glomerular filtration rate (eGFR) ≤20 mL/min/1.73 m2 from six European countries, we explored the association between longitudinal SBC and all-cause mortality in three separate CKD populations: pre-KRT, transition-CKD and in the KRT populations, using multivariable time-dependent Cox regression models. We evaluated effect modification by pre-specified variables on the relationship between SBC and mortality.

Results: We included 1485 patients with a median follow-up of 2.9 (interquartile range 2.7) years, during which 529 (35.6%) patients died. A U-shaped relationship between SBC levels and all-cause mortality was observed in the pre-KRT population (P = .03). Low cumulative exposure, defined as the area under the SBC trajectory before KRT initiation, was associated with increased mortality risk after transitioning to KRT (P = .01). Similarly, in the KRT population, low SBC levels showed a trend towards increased mortality risk (P = .13). We observed effect modification by subjective global assessment category (P-value for interaction = .02) and KRT (P-value for interaction = .02).

Conclusions: A U-shaped relationship describes the association between SBC and mortality in the advanced CKD pre-KRT population, whereas in the KRT population a trend towards an increased mortality risk was observed for low SBC levels.

Keywords: bicarbonate; chronic kidney disease; elderly; mortality.

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Conflict of interest statement

N.C.C. is member of the CKJ Editorial Board. The other authors have nothing to disclose with respect to the present research.

Figures

Figure 1:
Figure 1:
Flowchart of the study population.
Figure 2:
Figure 2:
Study design.
Figure 3:
Figure 3:
Kaplan–Meier survival curves for all-cause mortality based on quartiles of baseline SBC in the whole population. Results are displayed up to 5 years. The overall 5-year survival was 51% (95% CI 47, 54). Q_SBC, quartile of serum bicarbonate.
Figure 4:
Figure 4:
Continuous relationship between SBC and all-cause mortality in all study populations. Multivariable adjusted model, adjusted to age, sex, BMI, SGA, albumin, K+, eGFR, primary renal disease and comorbidities. Whole population, P-value nonlinear = .077; pre-KRT population, P-value nonlinear = .025; KRT population, P-value nonlinear = .126; transition-CKD population, P-value nonlinear = .119.
See this image and copyright information in PMC

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