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Open Access Research article

All-cause and cause-specific mortality associated with diabetes in prevalent hemodialysis patients

Abdus Sattar1, Christos Argyropoulos2, Lisa Weissfeld3, Nizar Younas2, Linda Fried2, John A Kellum4 and Mark Unruh5*

Author affiliations

1 Department of Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, USA

2 Renal and Electrolyte Division, University of Pittsburgh, Pittsburgh, USA

3 Department of Biostatistics, University of Pittsburgh, Pittsburgh, USA

4 Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, USA

5 Nephrology Division, University of New Mexico, Albuquerque, USA

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Citation and License

BMC Nephrology 2012, 13:130  doi:10.1186/1471-2369-13-130

Published: 1 October 2012

Abstract

Background

Diabetes is the most common risk factor for end-stage renal disease (ESRD) and has been associated with increased risk of death. In order to better understand the influence of diabetes on outcomes in hemodialysis, we examine the risk of death of diabetic participants in the HEMODIALYSIS (HEMO) study.

Methods

In the HEMO study, 823 (44.6%) participants were classified as diabetic. Using the Schoenfeld residual test, we found that diabetes violated the proportional hazards assumption. Based on this result, we fit two non-proportional hazard models: Cox’s time varying covariate model (Cox-TVC) that allows the hazard for diabetes to change linearly with time and Gray’s time-varying coefficient model.

Results

Using the Cox-TVC, the hazard ratio (HR) for diabetes increased with each year of follow up (p = 0.02) for all cause mortality. Using Gray’s model, the HR for diabetes ranged from 1.41 to 2.21 (p <0.01). The HR for diabetes using Gray’s model exhibited a different pattern, being relatively stable at 1.5 for the first 3 years in the study and increasing afterwards.

Conclusion

Risk of death associated with diabetes in ESRD increases over time and suggests that an increasing risk of death among diabetes may be underappreciated when using conventional survival models.

Keywords:
Cox regression; Diabetes; ESRD; Hemodialysis; Proportional hazard; Survival model; Time varying coefficient model; Time dependent covariate.