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The current deconstruction of paradoxes: one sign of the ongoing methodological “revolution”

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Abstract

The current deconstruction of paradoxes is one among several signs that a profound renewal of methods for clinical and epidemiological research is taking place; perhaps for some basic life sciences as well. The new methodological approaches have already deconstructed and explained long puzzling apparent paradoxes, including the (non-existent) benefits of obesity in diabetics, or of smoking in low birth weight. Achievements of the new methods also comprise the elucidation of the causal structure of long-disputed and highly complex questions, as Berkson’s bias and Simpson’s paradox, and clarifying reasons for deep controversies, as those on estrogens and endometrial cancer, or on adverse effects of hormone replacement therapy. These are signs that the new methods can go deeper and beyond the methods in current use. A major example of a highly relevant idea is: when we condition on a common effect of a pair of variables, then a spurious association between such pair is likely. The implications of these ideas are potentially vast. A substantial number of apparent paradoxes may simply be the result of collider biases, a source of selection bias that is common not just in epidemiologic research, but in many types of research in the health, life, and social sciences. The new approaches develop a new framework of concepts and methods, as collider, instrumental variables, d-separation, backdoor path and, notably, Directed Acyclic Graphs (DAGs). The current theoretical and methodological renewal—or, perhaps, “revolution”—may be changing deeply how clinical and epidemiological research is conceived and performed, how we assess the validity and relevance of findings, and how causal inferences are made. Clinical and basic researchers, among others, should get acquainted with DAGs and related concepts.

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Acknowledgments

We thank Julia del Amo, Arnaud Chiolero, Cesar Victora and three anonymous reviewers for insightful comments to earlier versions of the manuscript. The work was supported in part by research Grants from Instituto de Salud Carlos III—FEDER (FIS PI13/00020 and CIBER de Epidemiología y Salud Pública—CIBERESP), Government of Spain; Fundació La Marató de TV3 (20132910); and Government of Catalonia (2014 SGR 1012).

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Authors and Affiliations

  1. Hospital del Mar Institute of Medical Research (IMIM), Universitat Autònoma de Barcelona, Carrer del Dr. Aiguader, 88, 08003, Barcelona, Catalonia, Spain

    Miquel Porta

  2. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA

    Miquel Porta

  3. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain

    Miquel Porta & Francisco Bolúmar

  4. MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College, London, UK

    Paolo Vineis

  5. Human Genetics Foundation (HuGeF), Turin, Italy

    Paolo Vineis

  6. Faculty of Medicine, University of Alcalá, Alcalá de Henares, Madrid, Spain

    Francisco Bolúmar

  7. City University of New York School of Public Health at Hunter College, New York, NY, USA

    Francisco Bolúmar

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  1. Miquel Porta
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  2. Paolo Vineis
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Correspondence to Miquel Porta.

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Porta, M., Vineis, P. & Bolúmar, F. The current deconstruction of paradoxes: one sign of the ongoing methodological “revolution”. Eur J Epidemiol 30, 1079–1087 (2015). https://doi.org/10.1007/s10654-015-0068-8

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