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Eur J Epidemiol. 2010 Apr;25(4):245-51. doi: 10.1007/s10654-010-9451-7. Epub 2010 Apr 1.

Analysis of individual drug use as a time-varying determinant of exposure in prospective population-based cohort studies.

Author information

1
Department of Epidemiology, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands. b.stricker@erasmusmc.nl

Abstract

In pharmaco-epidemiology, the use of drugs is the determinant of interest when studying exposure-outcome associations. The increased availability of computerized information about drug use on an individual basis has greatly facilitated analyses of drug effects on a population-based scale. It seems likely that many negative findings in the early days of pharmaco-epidemiology can be explained by non-differential misclassification because of too simple (yes/no) exposure measures. In this paper, the authors discuss the importance of an adequate definition of drug exposure in pharmaco-epidemiological research and how this time-varying determinant can be analyzed in cohort studies. To reduce the risk of non-differential misclassification, a precise definition of exposure is mandatory and it is important to distinguish the complete follow-up period of a population into mutually exclusive episodes of non-use, past use and current use for each individual. By analyzing exposure to drugs as a time-dependent variable in a Cox regression model, cohort studies with complete coverage of all filled prescriptions can provide us with valid and precise risk estimates of drug-outcome associations. However, such estimates may be biased in the presence of time-dependent confounders which are themselves affected by prior exposure.

PMID:
20358262
PMCID:
PMC2850996
DOI:
10.1007/s10654-010-9451-7
[Indexed for MEDLINE]
Free PMC Article

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