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dc.contributor.authorGoldsmith, KAen_US
dc.contributor.authorChalder, Ten_US
dc.contributor.authorWhite, PDen_US
dc.contributor.authorSharpe, Men_US
dc.contributor.authorPickles, Aen_US
dc.date.accessioned2016-10-03T13:27:55Z
dc.date.issued2018-06en_US
dc.date.submitted2016-10-02T09:36:39.509Z
dc.identifier.urihttp://qmro.qmul.ac.uk/xmlui/handle/123456789/15687
dc.description.abstractClinical trials are expensive and time-consuming and so should also be used to study how treatments work, allowing for the evaluation of theoretical treatment models and refinement and improvement of treatments. These treatment processes can be studied using mediation analysis. Randomised treatment makes some of the assumptions of mediation models plausible, but the mediator-outcome relationship could remain subject to bias. In addition, mediation is assumed to be a temporally ordered longitudinal process, but estimation in most mediation studies to date has been cross-sectional and unable to explore this assumption. This study used longitudinal structural equation modelling of mediator and outcome measurements from the PACE trial of rehabilitative treatments for chronic fatigue syndrome (ISRCTN 54285094) to address these issues. In particular, autoregressive and simplex models were used to study measurement error in the mediator, different time lags in the mediator-outcome relationship, unmeasured confounding of the mediator and outcome, and the assumption of a constant mediator-outcome relationship over time. Results showed that allowing for measurement error and unmeasured confounding were important. Contemporaneous rather than lagged mediator-outcome effects were more consistent with the data, possibly due to the wide spacing of measurements. Assuming a constant mediator-outcome relationship over time increased precision.en_US
dc.description.sponsorshipFunding for the PACE trial was provided by the Medical Research Council, Department for Health for England, The Scottish Chief Scientist Office, and the Department for Work and Pensions. TC, AP and KG were in part supported by the National Institute for Health Research (NIHR) Biomedical Research Centre for Mental Health at the South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, Psychology & Neuroscience, Kings College London. KG was also funded by an NIHR Doctoral Fellowship, DRF-2011-04-061en_US
dc.format.extent1615 - 1633en_US
dc.languageengen_US
dc.relation.ispartofStat Methods Med Resen_US
dc.rights(c) The Author(s) 2016
dc.subjectMediationen_US
dc.subjectchronic fatigue syndromeen_US
dc.subjectclinical trialsen_US
dc.subjectlongitudinal mediation modelsen_US
dc.subjectmeasurement erroren_US
dc.subjectstructural equation modelsen_US
dc.titleMeasurement error, time lag, unmeasured confounding: Considerations for longitudinal estimation of the effect of a mediator in randomised clinical trials.en_US
dc.typeArticle
dc.identifier.doi10.1177/0962280216666111en_US
pubs.author-urlhttps://www.ncbi.nlm.nih.gov/pubmed/27647810en_US
pubs.issue6en_US
pubs.notesNot knownen_US
pubs.organisational-group/Queen Mary University of London
pubs.organisational-group/Queen Mary University of London/Faculty of Medicine & Dentistry
pubs.organisational-group/Queen Mary University of London/Faculty of Medicine & Dentistry/Wolfson Institute of Preventive Medicine
pubs.organisational-group/Queen Mary University of London/Faculty of Medicine & Dentistry/Wolfson Institute of Preventive Medicine/Psychiatry
pubs.organisational-group/Queen Mary University of London/REF
pubs.organisational-group/Queen Mary University of London/REF/Ref - UoA 02
pubs.publication-statusPublisheden_US
pubs.volume27en_US
qmul.funderThe PACE trial; A RCT of CBT, graded exercise, adaptive pacing and usual medical care for the chronic fatigue syndrome::Medical Research Councilen_US


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