Frailty, Inflammatory Markers, and Waitlist Mortality among Patients with End-stage Renal Disease in a Prospective Cohort Study

Background Among community-dwelling older adults, frailty is associated with heightened markers of inflammation and subsequent mortality. Although frailty is common among end-stage renal disease (ESRD) patients, the role of frailty and markers of inflammation in this population remains unclear. We quantified these associations in patients on the kidney transplant waitlist and tested whether frailty and/or markers of inflammation improve waitlist mortality risk prediction. Methods We studied 1975 ESRD patients on the kidney transplant waitlist (November 1, 2009, to February 28, 2017) in a multi-center cohort study of frailty. Serum inflammatory markers (interleukin-6 [IL-6], soluble tumor necrosis factor-α receptor-1 [sTNFR1], and C-reactive protein [CRP]) were analyzed in 605 of these participants; we calculated the inflammatory index score using IL-6 and sTNFR1. We compared the C-statistic of an established registry-based prediction model for waitlist mortality adding frailty and/or inflammatory markers (1 SD change in log IL-6, sTNFR1, CRP, or inflammatory index). Results The registry-based model had moderate predictive ability (c-statistic = 0.655). Frailty was associated with increased mortality (2.19; 95% confidence interval [CI], 1.26-3.79) but did not improve risk prediction (c-statistic = 0.646; P = 0.65). Like frailty, IL-6 (2.13; 95% CI, 1.41-3.22), sTNFR1 (1.70; 95% CI, 1.12-2.59), CRP (1.68; 95% CI, 1.06-2.67), and the inflammatory index (2.09; 95% CI, 1.38-3.16) were associated with increased mortality risk; unlike frailty, adding IL-6 (c-statistic = 0.777; P = 0.02), CRP (c-statistic = 0.728; P = 0.02), or inflammatory index (c-statistic = 0.777; P = 0.02) substantially improved mortality risk prediction. Conclusions Frailty and markers of inflammation were associated with increased waitlist mortality risk, but only markers of inflammation significantly improved ESRD risk prediction. These findings help clarify the accelerated aging physiology of ESRD and highlight easy-to-measure markers of increased waitlist mortality risk.