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Letter to the Editor

Published online by Cambridge University Press:  01 February 2007

Berit L Heitmann*
Affiliation:
Research Unit for Dietary Studies Institute of Preventive Medicine Center for Health and Society DK-1357 Copenhagen, Denmark
Lauren Lissner
Affiliation:
Department of Public Health and Community Sahlgrenska University Hospital Gothenborg UniversityGothenborg, Sweden
*
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Abstract

Type
Letter to the Editor
Copyright
Copyright © The Authors 2007

The authors reply in plain English

Sir,

We would like to thank Drs Thiébaut and Kipnis for their thoughtful comments. We agree that random reporting error is always present and results in attenuated associations. It is clearly necessary to recognise all types of error and their potential impact on epidemiological associations.

As the commentary correctly points out, we were not focusing on random error in our paperReference Heitmann and Lissner1. Even if in some cases random error may overwhelm biases from systematic error, this may not always be the case. Whether true associations are overestimated or underestimated depends on the magnitudes of these two types of error, as well as on the direction of the bias in relation to the underlying association. The purpose of our paper was to illustrate, not to prove, that non-random error can in theory inflate an association.

The effects of non-random errors on diet–disease associations are not always appreciated. For instance, in a recent re-analysis of data from the OPEN (Observing Protein and Energy Nutrition) study by a team including ourselves, Dr Kipnis and other researchers from National Cancer InsitituteReference Lissner, Troiano, Midthune, Heitmann, Kipnis and Subar2, we concluded that obesity-related reporting errors require much further investigation. Although the OPEN data are indeed unique in being able to characterise both types of error, it must be kept in mind that they are based on a highly selected study sample. Clearly, we need to improve our knowledge about person-specific and other non-random errors, as well as our ability to communicate about them.

References

1Heitmann, BL, Lissner, L. Can adverse effects of dietary fat intake be overestimated as a consequence of dietary fat underreporting? Public Health Nutrition 2005; 8: 1322–7.CrossRefGoogle ScholarPubMed
2Lissner, L, Troiano, RP, Midthune, D, Heitmann, BL, Kipnis, V, Subar, AF, et al. . OPEN about obesity: recovery biomarkers, dietary reporting errors, and BMI. International Journal of Obesity 2006; in press.Google Scholar