title: Linear mixed model approach to network meta-analysis for continuous outcomes in periodontal research.
abstract: OBJECTIVE
  Analysing continuous outcomes for network meta-analysis by means of linear mixed models is a great challenge, as it requires statistical software packages to specify special patterns of model error variance and covariance structure. This article demonstrates a non-Bayesian approach to network meta-analysis for continuous outcomes in periodontal research with a special focus on the adjustment of data dependency.
  
  
  METHODS
  Seventeen studies on guided tissue regeneration were used to illustrate how the proposed linear mixed models for network meta-analysis of continuous outcomes.
  
  
  RESULTS
  Arm-based network meta-analysis use treatment arms from each study as the unit of analysis; when patients are randomly assigned to each arm, data are deemed independent and therefore no adjustment is required for multi-arm trials. Trial-based network meta-analysis use treatment contrasts as the unit of analysis, and therefore treatment contrasts within a multi-arm trial are not independent. This data dependency occurs also in split-mouth studies, and adjustments for data dependency are therefore required.
  
  
  CONCLUSIONS
  Arm-based analysis is the preferred approach to network meta-analysis, when all included studies use the parallel group design and some compare more than two treatment arms. When included studies used designs that yield dependent data, the trial-based analysis is the preferred approach.
authors.affiliation: Institute of Epidemiology & Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Kang
authors.initials: YK
authors.lastname: Tu
mesh_terms: D000465:Algorithms; D018865:Dental Research / Q000706:statistics & numerical data*; D016557:Guided Tissue Regeneration, Periodontal / Q000706:statistics & numerical data; D006801:Humans; D016014:Linear Models; D015201:Meta-Analysis as Topic; D010517:Periodontics / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D012107:Research Design / Q000706:statistics & numerical data; D012196:Review Literature as Topic; D016896:Treatment Outcome
keywords: guided tissue regeneration; linear mixed model; mixed treatments comparisons; network meta-analysis; randomized controlled trials