Mortality in elderly hemodialysis patients, influence of frailty and comorbidity

Abstract

Background: Mortality in end-stage kidney disease (ESKD) remains high, especially among the elderly with a higher burden of comorbidity and frailty. In this group, dialysis may not offer better survival compared to conservative management. Frailty defined by clinical frailty scale (CFS) and comorbidity by Charlson Comorbidity Index (CCI) are known independent predictors of mortality. Our aim was to compare which one had higher impact on early mortality in urgent-start hemodialysis patients. Methods: We conducted a retrospective cohort study of patients aged 65 years and over, who started hemodialysis as their first renal replacement therapy (RRT) between January 2014 and December 2020. CFS and mCCI, at time of HD start, were used to evaluate, respectively, frailty and comorbid disease burden. The primary outcome was death in the first 6 months of RRT. Results: During the study period 166 patients were included. The median age, at time of hemodialysis start, was 75 years ± 6.3 years. The mortality at 6 months was 19% (n=31). For both scales, the analysis of ROC curve, stablished the optimal cut-off to predict the event death at first 6 months as ≥ 5points. The performance of CFS was superior to the mCCI, in fact, the area under the curve was significantly higher in CFS (0.739) versus the mCCI (0.620). A CFS≥5 had a sensitivity/specificity of 94%/44% in prediction the primary outcome. On the other hand, a mCCI≥5 predicts the same outcome with a sensitivity/specificity of 26%/88%. The diagnostic odds ratio for CFS≥5 was 11.6, compared to only 2.7 for mCCI≥5. Lastly, we constructed a model in which both scores interacted (as categorical variables), which after multivariable adjustment showed that mCCI/CFS <5/≥5 and ≥5/≥5 were independent predictors of mortality (HR=7.06; P=0.017; HR=10.708; P=0.002; respectively). Interestingly, no events were observed in the mCCI≥5/CFS<5 group. Conclusions: In this cohort of urgent-start incident HD patients, frailty defined by CFS was a stronger predictor of mortality than comorbidity defined by CCI.