Modeling the effect of time-dependent exposure on intensive care unit mortality

  • Martin WolkewitzEmail author
  • Jan Beyersmann
  • Petra Gastmeier
  • Martin Schumacher



To illustrate modern survival models with focus on the temporal dynamics of intensive care data. A typical situation is given in which time-dependent exposures and competing events are present.


We briefly review the following established statistical methods: logistic regression, regression models for event-specific hazards and the subdistribution hazard. These approaches are compared by showing advantages as well as disadvantages. All methods are applied to real data from a study of day-by-day ICU surveillance.


Standard logistic regression ignores the time-dependent nature of the data and is only a crude approach. Cumulative hazards and probability plots add important information and provide a deep insight into the temporal dynamics.


This paper might help to encourage researchers working in hospital epidemiology to apply adequate statistical models to complex medical questions.


Nosocomial infections Competing risks Event-specific hazard Subdistribution hazard Population attributable fraction 



Nosocomial pneumonia


Intensive care unit


Population attributable fraction


Odds ratio


Hazard ratio


Confidence interval


Proportional hazards regression



We thank the four anonymous reviewers for their comments and Caroline Mavergames for checking the final manuscript for English language grammar and style. They helped to improve the manuscript. This project was funded by the Deutsche Forschungsgemeinschaft DFG, project FOR 534.

Supplementary material

134_2009_1423_MOESM1_ESM.pdf (36 kb)
Supplementary material PDF (35 KB)


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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Martin Wolkewitz
    • 1
    • 2
  • Jan Beyersmann
    • 1
    • 2
  • Petra Gastmeier
    • 3
  • Martin Schumacher
    • 1
  1. 1.Institute of Medical Biometry and Medical InformaticsUniversity Medical Center FreiburgFreiburgGermany
  2. 2.Freiburg Centre for Data Analysis and ModellingUniversity of FreiburgFreiburgGermany
  3. 3.Institute of Hygiene and Environmental MedicineCharité-University Medicine BerlinBerlinGermany

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