SIMEX for correction of dietary exposure effects with Box-Cox transformed data |
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| Authors: | Timm Intemann Kirsten Mehlig Stefaan De Henauw Alfonso Siani Tassos Constantinou Luis A Moreno Dénes Molnár Toomas Veidebaum Iris Pigeot on behalf of the IFamily consortium |
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| Institution: | 1. Biometry and Data Management, Leibniz Institute for Prevention Research and Epidemiology–BIPS, Bremen, Germany;2. Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden;3. Department of Public Health, Ghent University, Ghent, Belgium;4. Institute of Food Sciences, National Research Council, Avellino, Italy;5. Research and Education Institute of Child Health, Strovolos, Cyprus;6. GENUD (Growth, Exercise, Nutrition and Development) Research Group, Instituto Agroalimentario de Aragón (IA2), Instituto de Investigación Sanitaria Aragón (IIS Aragón), Centro de Investigación Biomédica en Red Fisiopatologa de la Obesidad y Nutrición (CIBERObn), University of Zaragoza, Zaragoza, Spain;7. Department of Pediatrics, Medical School, University of Pécs, Pécs, Hungary;8. Department of Chronic Diseases, National Institute for Health Development, Tallinn, Estonia;9. Biometry and Data Management, Leibniz Institute for Prevention Research and Epidemiology–BIPS, Bremen, Germany
Institute of Statistics, Faculty of Mathematics and Computer Science, University of Bremen, Bremen, Germany |
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| Abstract: | Modelling dietary data, and especially 24-hr dietary recall (24HDR) data, is a challenge. Ignoring the inherent measurement error (ME) leads to biased effect estimates when the association between an exposure and an outcome is investigated. We propose an adapted simulation extrapolation (SIMEX) algorithm for modelling dietary exposures. For this purpose, we exploit the ME model of the NCI method where we assume the assumption of normally distributed errors of the reported intake on the Box-Cox transformed scale and of unbiased recalls on the original scale. According to the SIMEX algorithm, remeasurements of the observed data with additional ME are generated in order to estimate the association between the level of ME and the resulting effect estimate. Subsequently, this association is extrapolated to the case of zero ME to obtain the corrected estimate. We show that the proposed method fulfils the key property of the SIMEX approach, that is, that the MSE of the generated data will converge to zero if the ME variance converges to zero. Furthermore, the method is applied to real 24HDR data of the I.Family study to correct the effects of salt and alcohol intake on blood pressure. In a simulation study, the method is compared with the NCI method resulting in effect estimates with either smaller MSE or smaller bias in certain situations. In addition, we found our method to be more informative and easier to implement. Therefore, we conclude that the proposed method is useful to promote the dissemination of ME correction methods in nutritional epidemiology. |
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| Keywords: | 24-hr dietary recall measurement error correction method NCI method non-linear mixed model salt intake |
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