title: Longitudinal average attributable fraction as a method for studying time-varying conditions and treatments on recurrent self-rated health: the case of medications in older adults with multiple chronic conditions.
abstract: OBJECTIVE
  The objective is to modify the longitudinal extension of the average attributable fraction (LE-AAF) for recurrent outcomes with time-varying exposures and control for covariates.
  
  
  METHODS
  We included Medicare Current Beneficiary Survey participants with two or more chronic conditions enrolled from 2005 to 2009 with follow-up through 2011. Nine time-varying medications indicated for nine time-varying common chronic conditions and 14 of 18 forward-selected participant characteristics were used as control variables in the generalized estimating equations step of the LE-AAF to estimate associations with the recurrent universal health outcome self-rated health (SRH). Modifications of the LE-AAF were made to accommodate these indicated medication-condition interactions and covariates. Variability was empirically estimated by bias-corrected and accelerated bootstrapping.
  
  
  RESULTS
  In the adjusted LE-AAF, thiazide, warfarin, and clopidogrel had significant contributions of 1.2%, 0.4%, 0.2%, respectively, to low (poor or fair) SRH; whereas there were no significant contributions of the other medications to SRH. Hyperlipidemia significantly contributed 4.6% to high SRH. All the other conditions except atrial fibrillation contributed significantly to low SRH.
  
  
  CONCLUSIONS
  Our modifications to the LE-AAF method apply to a recurrent binary outcome with time-varying factors accounting for covariates.
authors.affiliation: Section of Geriatrics, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, CT; Department of Biostatistics, Yale School of Public Health, Yale University, New Haven, CT. Electronic address: Heather.Allore@Yale.edu.
authors.forename: Heather G
authors.initials: HG
authors.lastname: Allore
authors.affiliation: Department of Biostatistics, Yale School of Public Health, Yale University, New Haven, CT.
authors.forename: Yilei
authors.initials: Y
authors.lastname: Zhan
authors.affiliation: Section of Geriatrics, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, CT; Department of Chronic Disease, Yale School of Public Health, Yale University, New Haven, CT.
authors.forename: Mary
authors.initials: M
authors.lastname: Tinetti
authors.affiliation: Section of Geriatrics, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, CT.
authors.forename: Mark
authors.initials: M
authors.lastname: Trentalange
authors.affiliation: Section of Geriatrics, Department of Internal Medicine, Yale School of Medicine, Yale University, New Haven, CT.
authors.forename: Gail
authors.initials: G
authors.lastname: McAvay
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000367:Age Factors; D000368:Aged; D002908:Chronic Disease / Q000188:drug therapy*; D005260:Female; D006304:Health Status; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D055118:Medication Adherence; D015233:Models, Statistical; D057566:Self Report; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: Aged; Chronic disease; Epidemiologic methods; Longitudinal study