title: [Cohort studies].
abstract: This article about cohort studies is part of a methods series about study designs and their critical evaluation by the Ludwig Boltzmann Institute for Health Technology assessment. This article aims to describe the theoretical concept of cohort studies and their typical characteristics. Furthermore, it strives to highlight advantages and disadvantages of this study type and to make suggestions for the critical evaluation of the significance and validity of cohort studies. The article gives an account about characteristics due to the observational design and ways of acquiring control groups. Problems of blurring results by selection bias and confounding are also discussed. Cohort studies are applied in situations where the effects of environmental exposures are measured and rare side effects are identified but randomised controlled studies did not show significant results because of limitations. They are also used to assess the incidence of a disease or a condition.
authors.affiliation: Ludwig Boltzmann Institut für Health Technology Assessment, Wien, Austria. stefan.mathis@hta.lbg.ac.at
authors.forename: Stefan
authors.initials: S
authors.lastname: Mathis
authors.forename: Gerald
authors.initials: G
authors.lastname: Gartlehner
mesh_terms: D020811:Biomedical Technology / Q000592:standards; D016022:Case-Control Studies; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D003625:Data Collection; D003627:Data Interpretation, Statistical; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D015983:Selection Bias