title: Comparison of Estimates between Cohort and Case-Control Studies in Meta-Analyses of Therapeutic Interventions: A Meta-Epidemiological Study.
abstract: Observational studies are increasingly being used for assessing therapeutic interventions. Case-control studies are generally considered to have greater risk of bias than cohort studies, but we lack evidence of differences in effect estimates between the 2 study types. We aimed to compare estimates between cohort and case-control studies in meta-analyses of observational studies of therapeutic interventions by using a meta-epidemiological study.
  
  
  
  We used a random sample of meta-analyses of therapeutic interventions published in 2013 that included both cohort and case-control studies assessing a binary outcome. For each meta-analysis, the ratio of estimates (RE) was calculated by comparing the estimate in case-control studies to that in cohort studies. Then, we used random-effects meta-analysis to estimate a combined RE across meta-analyses. An RE < 1 indicated that case-control studies yielded larger estimates than cohort studies.
  
  
  
  The final analysis included 23 meta-analyses: 138 cohort and 133 case-control studies. Treatment effect estimates did not significantly differ between case-control and cohort studies (combined RE 0.97 [95% CI 0.86-1.09]). Heterogeneity was low, with between-meta-analysis variance τ2 = 0.0049. Estimates did not differ between case-control and prospective or retrospective cohort studies (RE = 1.05 [95% CI 0.96-1.15] and RE = 0.99 [95% CI, 0.83-1.19], respectively). Sensitivity analysis of studies reporting adjusted estimates also revealed no significant difference (RE = 1.03 [95% CI 0.91-1.16]). Heterogeneity was also low for these analyses.
  
  
  
  We found no significant difference in treatment effect estimates between case-control and cohort studies assessing therapeutic interventions.
authors.affiliation: Mailman School of Public Health, Columbia University, New York, United States of America.
authors.forename: Amy
authors.initials: A
authors.lastname: Lanza
authors.affiliation: Mailman School of Public Health, Columbia University, New York, United States of America.|INSERM U1153, Paris, France.|Université Paris Descartes - Sorbonne Paris Cité, Paris, France.|Assistance Publique-Hôpitaux de Paris, Hôpital Hôtel-Dieu, Centre d'Epidémiologie Clinique, Paris, France.|Cochrane France, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ravaud
authors.affiliation: INSERM U1153, Paris, France.|Assistance Publique-Hôpitaux de Paris, Hôpital Hôtel-Dieu, Centre d'Epidémiologie Clinique, Paris, France.
authors.forename: Carolina
authors.initials: C
authors.lastname: Riveros
authors.affiliation: INSERM U1153, Paris, France.|Université Paris Descartes - Sorbonne Paris Cité, Paris, France.|Assistance Publique-Hôpitaux de Paris, Hôpital Hôtel-Dieu, Centre d'Epidémiologie Clinique, Paris, France.|Cochrane France, Paris, France.
authors.forename: Agnes
authors.initials: A
authors.lastname: Dechartres
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D016021:Epidemiologic Studies; D006801:Humans; D015201:Meta-Analysis as Topic