title: Associated Factors and Consequences of Risk of Bias in Randomized Controlled Trials of Yoga: A Systematic Review.
abstract: BACKGROUND
  Bias in randomized controlled trials (RCTs) of complementary therapy interventions seems to be associated with specific factors and to potentially distort the studies' conclusions. This systematic review assessed associated factors of risk of bias and consequences for the studies' conclusions in RCTs of yoga as one of the most commonly used complementary therapies.
  
  
  METHODS
  Medline/PubMed, Scopus, IndMED and the Cochrane Library were searched through February 2014 for yoga RCTs. Risk of selection bias was assessed using the Cochrane tool and regressed to a) publication year; b) country of origin; c) journal type; and d) impact factor using multiple logistic regression analysis. Likewise, the authors' conclusions were regressed to risk of bias.
  
  
  RESULTS
  A total of 312 RCTs were included. Impact factor ranged from 0.0 to 39.2 (median = 1.3); 60 RCT (19.2%) had a low risk of selection bias, and 252 (80.8%) had a high or unclear risk of selection bias. Only publication year and impact factor significantly predicted low risk of bias; RCTs published after 2001 (adjusted odds ratio (OR) = 12.6; 95% confidence interval (CI) = 1.7, 94.0; p<0.001) and those published in journals with impact factor (adjusted OR = 2.6; 95%CI = 1.4, 4.9; p = 0.004) were more likely to have low risk of bias. The authors' conclusions were not associated with risk of bias.
  
  
  CONCLUSIONS
  Risk of selection bias was generally high in RCTs of yoga; although the situation has improved since the publication of the revised CONSORT statement 2001. Pre-CONSORT RCTs and those published in journals without impact factor should be handled with increased care; although risk of bias is unlikely to distort the RCTs' conclusions.
authors.affiliation: Department of Internal and Integrative Medicine, Kliniken Essen-Mitte, Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.|Australian Research Centre in Complementary and Integrative Medicine (ARCCIM), University of Technology Sydney, Sydney, Australia.
authors.forename: Holger
authors.initials: H
authors.lastname: Cramer
authors.affiliation: Department of Internal and Integrative Medicine, Kliniken Essen-Mitte, Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.
authors.forename: Jost
authors.initials: J
authors.lastname: Langhorst
authors.affiliation: Department of Internal and Integrative Medicine, Kliniken Essen-Mitte, Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.
authors.forename: Gustav
authors.initials: G
authors.lastname: Dobos
authors.affiliation: Department of Internal and Integrative Medicine, Kliniken Essen-Mitte, Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.|Australian Research Centre in Complementary and Integrative Medicine (ARCCIM), University of Technology Sydney, Sydney, Australia.
authors.forename: Romy
authors.initials: R
authors.lastname: Lauche
mesh_terms: D000529:Complementary Therapies / Q000379:methods; D006801:Humans; D016015:Logistic Models; D019122:Meditation / Q000523:psychology; D016032:Randomized Controlled Trials as Topic; D012306:Risk; D015983:Selection Bias; D015013:Yoga / Q000523:psychology*