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Dr Rachael Hughes

Dr Rachael Hughes

Dr Rachael Hughes
MSc, PhD(Bristol)

Senior Research Fellow

Office OS10
Oakfield House,
Oakfield Grove, Clifton BS8 2BN
(See a map)

+44 (0) 117 3310093


I am a research fellow in Medical Statistics within the MRC Integrative Epidemiology Unit. My main research interests are longitudinal modelling in life-course epidemiology, analysis in the presence of missing data, causal inference, instrumental variable analysis, longitudinal modelling of disease biomarkers, analysis in the presence of non-random selection into a study, and clinical epidemiology of HIV and AIDS in the era of antiretroviral therapy.

My research aspirations are to work at the interface of methodological development and application. I enjoy explaining complex statistical methods and interpreting their results to other researchers, evaluating and comparing statistical methods using simulation studies in real-world contexts, and providing user-friendly software to implement statistical methods unavailable to non-specialist researchers.

Activities / Findings

Publications in press

In a paper soon to be published in Epidemiology, we use directed acyclic graphs (DAGs) to depict assumptions about the selection mechanism (factors affecting selection) and show how DAGs can be used to determine when a two-stage least squares IV analysis is biased by different selection mechanisms. Via simulations, we show that selection can result in a biased IV estimate with substantial confi dence interval undercoverage, and the level of bias can differ between instrument strengths, a linear and nonlinear exposure-instrument association, and a causal and noncausal exposure effect.

Latest oral presentations at conferences

Invited seminar at the Bristol School of Mathematics. Selection bias when estimating average treatment effects using one-sample instrumental variable analysis, 15th February 2019.

Discussant for invited session Methods & Theory: Multilevel models: imputing level-2 missing data. From theory to practice at the Royal Statistical Society 2018 International Conference, Cardiff, September 2018.

Royal Statistical Society 2018 International Conference, Cardiff, September 2018.  “Selection bias in Instrumental Variable (IV) analyses” presented by Hughes RA; co-authors Davies NM, Davey Smith G, Tilling K. 

Joint International Society for Clinical Biostatistics and Australian Statistical Conference (ISCB ASC), Melbourne, August 2018. “Selection bias in Instrumental Variable (IV) analyses” presented by Hughes RA; co-authors Davies NM, Davey Smith G, Tilling K. 

External research positions

 I am associate editor for Biometrical Journal, and I am on the scientific conference board for the Royal Statistical Society.

Internal research positions

Currently, I am leading the missing data and non-random selection theme of the Integrative Epidemiology Unit 3 programme.

PhD Supervision

I co-supervise three PhD students. Satpal Sandhu is investigating multilevel modelling of repeated measures of growth of the maxilla (upper jaw) and the mandible (lower jaw). Elinor Curnow is looking at modelling event history after allogeneic haematopoietic stem cell transplantation in the presence of missing data. And, Matthew Tudball is investigating detecting and adjusting for selection bias within a Mendelian randomisation study.

Recent publications

View complete publications list in the University of Bristol publications system

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