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BMC Medical Research Methodology
Published in: BMC Medical Research Methodology 1/2016

Open Access 01-12-2016 | Research Article

Adjusting for overdispersion in piecewise exponential regression models to estimate excess mortality rate in population-based research

Authors: Miguel Angel Luque-Fernandez, Aurélien Belot, Manuela Quaresma, Camille Maringe, Michel P. Coleman, Bernard Rachet

Published in: BMC Medical Research Methodology | Issue 1/2016

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Abstract

Background

In population-based cancer research, piecewise exponential regression models are used to derive adjusted estimates of excess mortality due to cancer using the Poisson generalized linear modelling framework. However, the assumption that the conditional mean and variance of the rate parameter given the set of covariates x i are equal is strong and may fail to account for overdispersion given the variability of the rate parameter (the variance exceeds the mean). Using an empirical example, we aimed to describe simple methods to test and correct for overdispersion.

Methods

We used a regression-based score test for overdispersion under the relative survival framework and proposed different approaches to correct for overdispersion including a quasi-likelihood, robust standard errors estimation, negative binomial regression and flexible piecewise modelling.

Results

All piecewise exponential regression models showed the presence of significant inherent overdispersion (p-value <0.001). However, the flexible piecewise exponential model showed the smallest overdispersion parameter (3.2 versus 21.3) for non-flexible piecewise exponential models.

Conclusion

We showed that there were no major differences between methods. However, using a flexible piecewise regression modelling, with either a quasi-likelihood or robust standard errors, was the best approach as it deals with both, overdispersion due to model misspecification and true or inherent overdispersion.
Appendix
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Metadata
Title
Adjusting for overdispersion in piecewise exponential regression models to estimate excess mortality rate in population-based research
Authors
Miguel Angel Luque-Fernandez
Aurélien Belot
Manuela Quaresma
Camille Maringe
Michel P. Coleman
Bernard Rachet
Publication date
01-12-2016
Publisher
BioMed Central
Published in
BMC Medical Research Methodology / Issue 1/2016
Electronic ISSN: 1471-2288
DOI
https://doi.org/10.1186/s12874-016-0234-z

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