title: The Effectiveness of Blended Learning in Health Professions: Systematic Review and Meta-Analysis.
abstract: BACKGROUND
  Blended learning, defined as the combination of traditional face-to-face learning and asynchronous or synchronous e-learning, has grown rapidly and is now widely used in education. Concerns about the effectiveness of blended learning have led to an increasing number of studies on this topic. However, there has yet to be a quantitative synthesis evaluating the effectiveness of blended learning on knowledge acquisition in health professions.
  
  
  OBJECTIVE
  We aimed to assess the effectiveness of blended learning for health professional learners compared with no intervention and with nonblended learning. We also aimed to explore factors that could explain differences in learning effects across study designs, participants, country socioeconomic status, intervention durations, randomization, and quality score for each of these questions.
  
  
  METHODS
  We conducted a search of citations in Medline, CINAHL, Science Direct, Ovid Embase, Web of Science, CENTRAL, and ERIC through September 2014. Studies in any language that compared blended learning with no intervention or nonblended learning among health professional learners and assessed knowledge acquisition were included. Two reviewers independently evaluated study quality and abstracted information including characteristics of learners and intervention (study design, exercises, interactivity, peer discussion, and outcome assessment).
  
  
  RESULTS
  We identified 56 eligible articles. Heterogeneity across studies was large (I(2) ≥93.3) in all analyses. For studies comparing knowledge gained from blended learning versus no intervention, the pooled effect size was 1.40 (95% CI 1.04-1.77; P<.001; n=20 interventions) with no significant publication bias, and exclusion of any single study did not change the overall result. For studies comparing blended learning with nonblended learning (pure e-learning or pure traditional face-to-face learning), the pooled effect size was 0.81 (95% CI 0.57-1.05; P<.001; n=56 interventions), and exclusion of any single study did not change the overall result. Although significant publication bias was found, the trim and fill method showed that the effect size changed to 0.26 (95% CI -0.01 to 0.54) after adjustment. In the subgroup analyses, pre-posttest study design, presence of exercises, and objective outcome assessment yielded larger effect sizes.
  
  
  CONCLUSIONS
  Blended learning appears to have a consistent positive effect in comparison with no intervention, and to be more effective than or at least as effective as nonblended instruction for knowledge acquisition in health professions. Due to the large heterogeneity, the conclusion should be treated with caution.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tongji Medical College of Huazhong University of Science &Technology, Wuhan, China.
authors.forename: Qian
authors.identifier: http://orcid.org/0000-0003-0646-7245
authors.initials: Q
authors.lastname: Liu
authors.forename: Weijun
authors.identifier: http://orcid.org/0000-0003-3407-6882
authors.initials: W
authors.lastname: Peng
authors.forename: Fan
authors.identifier: http://orcid.org/0000-0002-5995-7953
authors.initials: F
authors.lastname: Zhang
authors.forename: Rong
authors.identifier: http://orcid.org/0000-0002-0946-7286
authors.initials: R
authors.lastname: Hu
authors.forename: Yingxue
authors.identifier: http://orcid.org/0000-0002-1986-9406
authors.initials: Y
authors.lastname: Li
authors.forename: Weirong
authors.identifier: http://orcid.org/0000-0003-0533-4555
authors.initials: W
authors.lastname: Yan
mesh_terms: D020375:Education, Distance; D004517:Education, Professional / Q000379:methods*; D006281:Health Occupations / Q000193:education*; D006801:Humans
keywords: blended learning; effectiveness; health professions; knowledge; meta-analysis