Health status as a potential mediator of the association between hemodialysis vascular access and mortality

Vanessa Grubbs*, Haimanot Wasse, Eric Vittinghoff, Barbara A. Grimes, Kirsten L. Johansen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


BackgroundIt is unknown whether the selection of healthier patients for ateriovenous fistula (AVF) placement explains higher observed catheter-associated mortality among elderly hemodialysis patients.MethodsFrom the United States Renal Data System 2005-2007, we used proportional hazard models to examine 117 277 incident hemodialysis patients aged 67-90 years for the association of initial vascular access type and 5-year mortality after accounting for health status. Health status was defined as functional status at dialysis initiation and number of hospital days within 2 years prior to dialysis initiation.ResultsPatients with catheter alone had more limited functional status (25.5 versus 10.8% of those with AVF) and 3-fold more prior hospital days than those with AVF (mean 18.0 versus 5.4). In the unadjusted model, the likelihood of death was higher for arteriovenous grafts (AVG) Hazard ratio (HR) 1.20 [95% CI (1.16-1.25)], catheter plus AVF [HR 1.34 (1.31-1.38)], catheter plus AVG [HR 1.46 (1.40-1.52)] and catheter only [HR 1.95 (1.90-1.99)], compared with AVF (P < 0.001). The association attenuated -23.7% (95% CI -22.0, -25.5) overall (AVF versus all other access types) after adjusting for the usual covariates (including sociodemographics, comorbidities and pre-dialysis nephrology care) AVG [HR 1.21 (1.17-1.26)], catheter plus AVF [HR 1.27 (1.24-1.30)], catheter plus AVG [HR 1.38 (1.32-1.43)] and catheter only [HR 1.69 (1.66-1.73)], P < 0.001. Additional adjustment for health status further attenuated the association by another -19.7% (-18.2, -21.3) overall but remained statistically significant <AVG [HR 1.18 (1.13-1.22)], catheter plus AVF [HR 1.20 (1.17-1.23)], catheter plus AVG HR 1.38 [1.26 (1.21-1.31)] and catheter only [HR 1.54 (1.50-1.58)], P < 0.001>.ConclusionsThe observed attenuation in mortality differences previously attributed to access type alone suggests the existence of selection bias. Nevertheless, the persistence of an apparent survival advantage after adjustment for health status suggests that AVF should still be the access of choice for elderly individuals beginning hemodialysis until more definitive data eliminating selection bias become available.

Original languageEnglish (US)
Pages (from-to)892-898
Number of pages7
JournalNephrology Dialysis Transplantation
Issue number4
StatePublished - Apr 2014
Externally publishedYes


  • elderly
  • hemodialysis
  • mortality
  • vascular access

ASJC Scopus subject areas

  • Nephrology
  • Transplantation


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