Occupational and Environmental Medicine. 2014 June. [Link]
Lacourt A, Leveque E, Leffondre K.
In case-control studies on cancer, occupational exposure to a specific agent is often summarised through a cumulative index of exposure at the time of diagnosis/interview. This cumulative index is the sum, over all years of exposure to the agent, of the dose received each year. This gives the same weight to each dose, whether this dose was received in the first years of exposure or at a shorter distant time from the diagnosis/interview. This assumption is unlikely to be reasonable for asbestos and mesothelioma. The objectives of this study were to estimate the weight of each dose of asbestos received in the past, and to compare the risk of mesothelioma associated with different profiles of exposure, using French case-control data.
From a French case-control study, 1199 male cases and 2379 male controls were recruited in 1987-2006. Occupational asbestos exposure was assessed using a job exposure matrix, and represented in logistic regression models by a flexible time-dependent weighted function of the dose.
The impact of a given increase of the dose depended on when the dose was received. It allowed us to compare the risk of subjects who were exposed for a long duration at a low dose with subjects who were shortly exposed to a high dose at different distant times from diagnosis/interview.
This study provides new insights on the dose-time-response relationship between occupational asbestos and mesothelioma, and an illustration of the use of an approach that could be of interest for other associations.