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The effect of censoring on cancer risk estimates based on the Canadian National Dose Registry of occupational radiation exposure.

Authors
Shin-H; Ramsay-T; Krewski-D; Zielinski-JM
Source
J Expo Anal Environ Epidemiol 2005 Sep; 15(5):398-406
NIOSHTIC No.
20028993
Abstract
Cohort studies represent an important epidemiological tool for exploring the potential adverse health effects of low-dose exposure to ionizing radiation in the workplace. Analyses of data from the National Dose Registry of Canada have suggested that occupational radiation exposure leads to increased risk of several specific types of cancer, as well as increased overall risk of cancer. An important aspect of such studies is the censoring in recorded exposures induced by dosimetry detection limits. Such a censoring effect can lead to significant underestimation of cumulative doses which, in turn, can result in overestimation of the excess cancer risk associated with occupational radiation exposure. In this article, we present analytic results, supported by a simulation study, on the magnitude of overestimation of risk based on the additive relative risk model used in the analysis of the NDR data that can occur due to censoring. Our results indicate that overestimation of risk is modest, being less than 20% in all situations considered here. Because censoring also results in ovestimation of the precision of the risk estimates, the significance levels of Wald-type statistical tests for increased risk based on the ratio of the estimate to its standard error are virtually unaffected by censoring. These results suggest that although the application of the additive excess relative risk model in the presence of censoring may lead to some overestimation of risk, the model does not lead to invalid conclusions regarding the association between occupational radiation exposure and cancer risk based on data from the NDR.
Keywords
Cancer; Occupational-exposure; Radiation; Radiation-exposure; Epidemiology; Ionizing-radiation; Risk-factors; Risk-analysis; Dosimetry; Models
Contact
Timothy Ramsay, R. Samuel McLaughlin Centre for Population Health Risk Assessment, One Stewart Street, Room 321, Ottawa, ON, Canada K1N 6N5
CODEN
JEAEE9
Publication Date
20050901
Document Type
Journal Article
Email Address
tramsay@uottawa.ca
Funding Type
Grant
Fiscal Year
2005
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-007864
Issue of Publication
5
ISSN
1053-4245
Source Name
Journal of Exposure Analysis and Environmental Epidemiology
State
WA
Performing Organization
Fred Hutchinson Cancer Research Center
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