Finally, the statistical techniques used in the exposure–response
model have evolved from Poisson regression techniques
to Cox proportional hazards model techniques. Poisson regression
techniques were readily available from the beginning. However,
the first step in Poisson regressions is to create exposure categories
which categorize the person-years in an individual’s exposure history
into specified intervals. This categorization discards much of
the information in the individual exposure histories that UAB has
captured in their job-exposure matrices. On the other hand, Cox
proportional hazards models allow the exposure in the model to
be whatever specific values each worker had in his work history
and how that exposure changed over time. Because UAB made
the individual exposure histories available (under a confidentiality
agreement) and our exposure–response modeling had evolved
from Poisson to Cox modeling, the analysis did not have to rely
on reported categorical results and Poisson regression.
Furthermore, the individual exposure histories in the most recent
UAB data could be fully incorporated into the exposure–response
Cox modeling reported previously [22,23] and herein.