Analysis of Occupational Cohort Data Using Exposure as a Continuous Time-dependent Variable

Maria Lorenzi successfully defended her M.Sc. project entitled "Analysis of Occupational Cohort Data Using Exposure as a Continuous Time-dependent Variable" on 3 August 2005.

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 analyzed 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 dose-response 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 dose-response curve nonparametrically for a study of aluminium smelter workers conducted by the British Columbia Cancer Agency and compare the results to the categorical analyses.

This type of interdisciplinary work is a hallmark of our program in Applied Statistics at Simon Fraser University. For more information, please contact Maria Lorenzi ( or her supervisor John Spinelli (, BC Cancer Agency and Department of Statistics and Actuarial Science.

3 August 2005.