Assessing causality in epidemiology: revisiting Bradford Hill to incorporate developments in causal thinking

Shimonovich, M., Pearce, A. , Thomson, H. , Keyes, K. and Katikireddi, S. V. (2021) Assessing causality in epidemiology: revisiting Bradford Hill to incorporate developments in causal thinking. European Journal of Epidemiology, 36(9), pp. 873-887. (doi: 10.1007/s10654-020-00703-7) (PMID:33324996) (PMCID:PMC8206235)

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The nine Bradford Hill (BH) viewpoints (sometimes referred to as criteria) are commonly used to assess causality within epidemiology. However, causal thinking has since developed, with three of the most prominent approaches implicitly or explicitly building on the potential outcomes framework: directed acyclic graphs (DAGs), sufficient-component cause models (SCC models, also referred to as ‘causal pies’) and the grading of recommendations, assessment, development and evaluation (GRADE) methodology. This paper explores how these approaches relate to BH’s viewpoints and considers implications for improving causal assessment. We mapped the three approaches above against each BH viewpoint. We found overlap across the approaches and BH viewpoints, underscoring BH viewpoints’ enduring importance. Mapping the approaches helped elucidate the theoretical underpinning of each viewpoint and articulate the conditions when the viewpoint would be relevant. Our comparisons identified commonality on four viewpoints: strength of association (including analysis of plausible confounding); temporality; plausibility (encoded by DAGs or SCC models to articulate mediation and interaction, respectively); and experiments (including implications of study design on exchangeability). Consistency may be more usefully operationalised by considering an effect size’s transportability to a different population or unexplained inconsistency in effect sizes (statistical heterogeneity). Because specificity rarely occurs, falsification exposures or outcomes (i.e., negative controls) may be more useful. The presence of a dose-response relationship may be less than widely perceived as it can easily arise from confounding. We found limited utility for coherence and analogy. This study highlights a need for greater clarity on BH viewpoints to improve causal assessment.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Shimonovich, Ms Michal and Pearce, Dr Anna and Katikireddi, Professor Vittal and Thomson, Dr Hilary
Authors: Shimonovich, M., Pearce, A., Thomson, H., Keyes, K., and Katikireddi, S. V.
College/School:College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > MRC/CSO SPHSU
University Services > Learning and Teaching Services Division
Journal Name:European Journal of Epidemiology
ISSN (Online):1573-7284
Published Online:16 December 2020
Copyright Holders:Copyright © 2020 The Authors
First Published:First published in European Journal of Epidemiology 36(9): 873-887
Publisher Policy:Reproduced under a Creative Commons licence

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
727651SPHSU Core Renewal: Measuring and Analysing Socioeconomic Inequalities in Health Research ProgrammeAlastair LeylandMedical Research Council (MRC)MC_UU_12017/13IHW - MRC/CSO SPHU
Chief Scientist Office (CSO)SPHSU13
727671SPHSU Core Renewal: Informing Healthy Public Policy Research ProgrammePeter CraigMedical Research Council (MRC)MC_UU_12017/15IHW - MRC/CSO SPHU
Chief Scientist Office (CSO)SPHSU15