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Consideration of measurement errors in the analysis of the risk associated with exposure to ionizing radiation in an occupational cohort: application to the French uranium miners’ cohort

Rodrigue Sètchéou Allodji has defended his thesis on the 9th December 2011 in Villejuif.

Document type > *Mémoire/HDR/Thesis

Keywords >

Research Unit > IRSN/DRPH/SRBE/LEPID

Authors > ALLODJI Sètchéou Rodrigue

Publication Date > 09/12/2011

Summary

In epidemiological studies, measurement errors in exposure can substantially bias the
estimation of the risk associated to exposure. A broad variety of methods for measurement error correction has been developed, but they have been rarely applied in practice, probably because their ability to correct measurement error effects and their implementation are poorly understood. Another important reason is that many of the proposed correction methods require to know measurement errors characteristics (size, nature, structure and distribution).


The aim of this thesis is to take into account measurement error in the analysis of risk
of lung cancer death associated to radon exposure based on the French cohort of uranium miners. The mains stages were (1) to assess the characteristics (size, nature, structure and distribution) of measurement error in the French uranium miners cohort, (2) to investigate the impact of measurement error in radon exposure on the estimated excess relative risk (ERR) of lung cancer death associated to radon exposure, and (3) to compare the performance of methods for correction of these measurement error effects.


The French cohort of uranium miners includes more than 5000 miners chronically
exposed to radon with a follow-up duration of 30 years. Measurement errors have been characterized taking into account the evolution of uranium extraction methods and of radiation protection measures over time. A simulation study based on the French cohort of uranium miners has been carried out to investigate the effects of these measurement errors on the estimated ERR and to assess the performance of different methods for correcting these effects.


Measurement error associated to radon exposure decreased over time, from more than 45% in the early 70’s to about 10% in the late 80’s. Its nature also changed over time from mostly Berkson to classical type from 1983. Simulation results showed that measurement error leads to an attenuation of the ERR towards the null, with substantial bias on ERR estimates in the order of 60%. All three error-correction methods allowed a noticeable but partial reduction of the attenuation bias. An advantage was observed for the simulationextrapolation method (SIMEX) in our context, but the performance of the three correction methods highly depended on the accurate determination of the characteristics of measurement error.


This work illustrates the importance of measurement error correction in order to obtain reliable estimates of the exposure-risk relationship between radon and lung cancer. Corrected risk estimates should prove of great interest in the elaboration of protection policies against radon in radioprotection and in public health.


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