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Editorial
. 2025 Feb 1;192(2):E1-E3.
doi: 10.1093/ejendo/lvaf014.

When selection becomes selection bias

Kristina Laugesen  1   2 , Olaf M Dekkers  1   3 , Rolf H H Groenwold  3 , Nils Skajaa  1
Affiliations
Editorial

When selection becomes selection bias

Kristina Laugesen et al. Eur J Endocrinol. .

Abstract

Selection in clinical research does not necessarily result in selection bias. To understand when selection leads to bias, we discuss collider-conditioning bias, which is a common and often self-inflicted type of selection bias. Collider-conditioning bias may be difficult to recognize, and paying more attention to the bias could therefore increase the quality of research. In this paper, we aim to increase awareness and understanding of the topic.

Keywords: collider; directed acyclic graphs; obesity paradox; selection bias.

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Conflict of interest statement

Conflict of interest: O.M.D. is a Deputy Editor for European Journal of Endocrinology. He was not involved in the review or editorial process for this paper, on which he is listed as an author. K.L. and R.H.H.G. report no conflicts of interest. N.S. was affiliated with the Department of Clinical Epidemiology, Aarhus University and Aarhus University Hospital, during the initiation of this study, but is now employed by Novo Nordisk A/S.

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