Abstract
Much research in environmental epidemiology relies on aggregate-level information on exposure to potentially toxic substances and on relevant covariates. We compare the use of additive (linear) and multiplicative (log-linear) regression models for the analysis of such data. We illustrate how both additive and multiplicative models can be fit to aggregate-level data sets in which disease incidence is the dependent variable, and contrast these results with similar models fitted to individual-level data. We find (1) that for aggregate-level data, multiplicative models are more likely than additive models to introduce bias into the estimation of rates, an effect not found with individual-level data; and (2) that under many circumstances multiplicative models reduce the precision of the estimates, an effect also not found in individual-level models. For both additive and multiplicative models of aggregate-level data, we find that, in the presence of covariates, narrow confidence interval are obtained only when two or more antecedent factors are strongly related to the measured covariate and/or the exposure of primary substantive interest. We conclude that the equivalency of fitting additive versus multiplicative models in studies with individual-level binary data does not carry over to studies that analyze aggregate-level information. For aggregate data, we strongly recommend use of additive models.
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Supported by Grant #1 U19 EH000102 from the National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA.
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Thompson, W.D., Wartenberg, D. Additive versus multiplicative models in ecologic regression. Stoch Environ Res Risk Assess 21, 635–646 (2007). https://doi.org/10.1007/s00477-007-0141-2
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DOI: https://doi.org/10.1007/s00477-007-0141-2