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1、Dynamicpathanalysis-AusefultooltoinvestigatemediationprocessesinclinicalsurvivaltrialsSusanneStrohmaier,KjetilRøysland,RuneHoff,ØrnulfBorgan,TerjeRPedersen,OddO.AalenApril27,2015AbstractWhenitcomestoclinicalsurvivaltrials,regulatoryrestrictionsusuallyrequiretheapplicati
2、onofmethodsthatsolelyutilizebaselinecovariatesandtheintention-to-treatprinciple.Therebyalotofpotentiallyusefulinformationislost,ascollectionoftime-to-eventdataoftengoeshandinhandwithcollectionofinformationonbiomarkersandotherinternaltime-dependentcovari-ates.However,th
3、erearetoolstoincorporateinformationfromrepeatedmeasurementsinausefulmannerthatcanhelptoshedmorelightontheunderlyingtreatmentmechanisms.Weconsiderdynamicpathanalysis,amodelformediationanalysisinthepresenceofatime-to-eventoutcomeandtime-dependentcovariatestoinvestigatedi
4、rectandindirecteffectsinastudyofdifferentlipidloweringtreatmentsinpatientswithpreviousmyocardialinfarctions.Further,weaddressthequestionwhethersurvivalinitselfmayproduceassociationsbetweenthetreatmentandthemediatorindynamicpathanalysisandgiveanargumentthat,duetolinearity
5、oftheassumedadditivehazardmodel,thisisnotthecase.Wefurtherelaborateonourviewthat,whenstudyingmediation,weareactuallydealingwithunderlyingprocessesratherthansinglevariablesmea-suredonlyonceduringthestudyperiod.Thisbecomesapparentinresultsfromvariousmodelsappliedtothestu
6、dyoflipidloweringtreatmentsaswellasouradditionallyconductedsimulationstudy,whereweclearlyobserve,thatdiscardinginformationonrepeatedmeasurementscanleadtopotentiallyerroneousconclusions.1IntroductionSurvivalandeventhistoryanalysishasbecomeacentralinterestinclinicalbiost
7、atistics,asmanyclini-caltrialsaredesignedtoinvestigatetheeffectofcertaintreatmentsonthetimeuntiltheoccurrenceofaparticulareventofinterest,suchasdeathordiseaseprogression.Asrequiredbyregulatoryauthori-ties,typicalapproachestoassesstheseeffectscompriseofKaplan-Meierplotsal
8、ongwithlog-ranktestsarXiv:1504.06506v1[stat.ME]24Apr2015orofemployingaCoxregressionmodelincludingtreatmentandbaseline
