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Cited by 1,708

The DOI matches its Crossref record; 3 of the 3 references it cites were found in a registry or an index.

Immortal Time Bias in Pharmacoepidemiology

Suissa, S.·2008·American Journal of Epidemiology
DOI 10.1093/aje/kwm324
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Abstract

Immortal time is a span of cohort follow-up during which, because of exposure definition, the outcome under study could not occur. Bias from immortal time was first identified in the 1970s in epidemiology in the context of cohort studies of the survival benefit of heart transplantation. It recently resurfaced in pharmaco-epidemiology, with several observational studies reporting that various medications can be extremely effective at reducing morbidity and mortality. These studies, while using different cohort designs, all involved some form of immortal time and the corresponding bias. In this paper, the author describes various cohort study designs leading to this bias, quantifies its magnitude under different survival distributions, and illustrates it by using data from a cohort of lung cancer patients. The author shows that for time-based, event-based, and exposure-based cohort definitions, the bias in the rate ratio resulting from misclassified or excluded immortal time increases proportionately to the duration of immortal time. The bias is more pronounced with a decreasing hazard function for the outcome event, as illustrated with the Weibull distribution compared with a constant hazard from the exponential distribution. In conclusion, observational studies of drug benefit in which computerized databases are used must be designed and analyzed properly to avoid immortal time bias.

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Crossref · 10.1093/aje/kwm324

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3 of 3 references verified0 citation errors · 0 not checkable

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Metadata

Authors
Suissa, S.
Venue
American Journal of Epidemiology
Publisher
Oxford University Press (OUP)
Published
2008-01-07
Volume
167
Issue
4
Pages
492-499
ISSN
  • 0002-9262
  • 1476-6256
DOI
10.1093/aje/kwm324
Cited by
1,708
References
3
Language
en

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