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. 2018 Apr:125:79-82.
doi: 10.1016/j.resuscitation.2018.02.006. Epub 2018 Feb 6.

"Resuscitation time bias"-A unique challenge for observational cardiac arrest research

Lars W Andersen  1 , Anne V Grossestreuer  2 , Michael W Donnino  3
Affiliations

"Resuscitation time bias"-A unique challenge for observational cardiac arrest research

Lars W Andersen et al. Resuscitation. 2018 Apr.

Abstract

Observational studies are prone to a number of biases. One of these is immortal time bias. In this manuscript, we discuss immortal time bias as it pertains to post-cardiac arrest research and describes a related bias which we term "resuscitation time bias". This bias can occur when studying exposures during cardiac arrest. In this unique situation, an exposure is more likely to occur the longer the cardiac arrest continues. Since length of resuscitation is strongly associated with worse outcome, this will bias the results toward a harmful effect of the exposure. We discuss this bias and present methods to account for it.

Keywords: Bias; Epidemiology; Immortal time bias; Resuscitation.

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Conflict of interest statement

Conflict of interest statement

None of the authors have any conflicts of interest.

Figures

Fig. 1.
Fig. 1.
Immortal time bias. Graphical example illustrating immortal time bias. Due to the way exposure is defined, patients in the exposed group are “immortal” until they receive the exposure. This artificially favors patients in the exposed group, biasing the results.
Fig. 2.
Fig. 2.
Resuscitation time bias. Graphical example illustrating resuscitation time bias. Due to the way the exposure is defined, patients in the exposed group have longer cardiac arrest. Since longer cardiac arrests are associated with poor outcomes, this artificially favors the unexposed group, biasing the results.
Fig. 3.
Fig. 3.
Risk set matching. Graphical illustration of risk set matching. By comparing the exposed to unexposed who are at risk of the exposure (i.e. still in cardiac arrest), resuscitation time bias is essentially eliminated.
Fig. 4.
Fig. 4.
Example of risk set matching. See text for details. Adopted with permission from Andersen and Donnino [25].
See this image and copyright information in PMC

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