Analysis of occupational cohort data using exposure as a continuous time-dependent variable

In occupational cohort studies, a group of workers is followed over time, and disease and work history information are collected for each individual in order to determine whether exposure to a particular substance is linked to differences in mortality or disease incidence rates. These studies are typically analysed by treating cumulative exposure as a categorical variable and then comparing disease or mortality rates between different exposure groups. A main shortfall of such analyses is a heavy dependence on the choice of these exposure categories, as certain choices may mask or exaggerate important features of the doseresponse curve. In this project, an extension to the Cox proportional hazards model is used to treat cumulative exposure as a continuous variable and model the doseresponse curve nonparametrically for a study of aluminium smelter workers conducted by the British Columbia Cancer Agency and compare the results to the categorical analyses.