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Regular readers of In Brief will have noticed frequent references to Cochrane Reviews. Scientists invariably review the existing evidence on a topic as a prelude to new primary research, and sometimes seek to increase the power of research by considering the work of multiple researchers simultaneously. Cochrane Reviews are the gold standard for research reviews and meta-analyses. Cochrane commissions reviews of health research that adhere to rigorous standards to maximise their reliability, quality and authority.

In this article, we explain what Cochrane is, how it came about, how it operates, and its influence.

What is Cochrane?

Cochrane (initially the Cochrane Collaboration) is ‘a global independent network of researchers, professionals, patients, carers, and people interested in health’. It consists of 37 000 volunteer contributors – many of whom are leaders in their fields and work in the world’s most respected academic and medical institutions – from more than 130 countries.

Cochrane’s mission is to provide accessible, credible information to support informed decision-making. As the volume of health evidence and access to it increases, the risks of misinterpreting complex content increase correspondingly, and obtaining a complete and balanced picture becomes more difficult. Cochrane contributors’ evaluations of medical evidence inform health workers and researchers in many fields and underpin the drive to improve global health.

Cochrane’s history

Cochrane is named in honour of Archie Cochrane, a British medical researcher who contributed greatly to the development of epidemiology. He is best known for Effectiveness and Efficiency: Random reflections on health services (1972), in which he suggested that, since resources would always be limited, they should be used to ‘provide equitably those forms of health care which had been shown in properly designed evaluations to be effective’. In particular, he stressed the importance of using evidence from randomised controlled trials (RCTs) because they provide much more reliable information than other sources of evidence.

In 1979 Cochrane wrote ‘It is surely a great criticism of our profession that we have not organised a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomised controlled trials’. In the 1980s, in response to this challenge, an international collaboration developed the Oxford Database of Perinatal Trials.

In 1987, Cochrane called a systematic review of RCTs of care during pregnancy and childbirth ‘a real milestone in the history of randomized trials and in the evaluation of care’, and suggested that other specialties should copy its methods. Other researchers supported his views, and this led to the founding of the Cochrane Collaboration in 1993.

How Cochrane works

Contributors are organised into Cochrane groups: healthcare subject-related review groups, thematic networks, groups concerned with the methodology of systematic reviews, and regional centres. Contributors affiliate themselves to one or more groups based on their interests, expertise and/or geographical location.

Cochrane’s work is based on 10 key principles:

1 Collaboration by fostering global cooperation, teamwork, and open and transparent communication and decision-making
2 Building on the enthusiasm of individuals by involving, supporting and training people of different skills and backgrounds
3 Avoiding duplication of effort by good management, coordination and effective internal communications to maximise economy of effort
4 Minimising bias through a variety of approaches such as scientific rigour, ensuring broad participation, and avoiding conflicts of interest
5 Keeping up-to-date by a commitment to ensure that Cochrane Systematic Reviews are maintained through identification and incorporation of new evidence
6 Striving for relevance by promoting the assessment of health questions using outcomes that matter to people making choices in health and health care
7 Promoting access by wide dissemination of our outputs, taking advantage of strategic alliances, and by promoting appropriate access models and delivery solutions to meet the needs of users worldwide
8 Ensuring Quality by applying advances in methodology, developing systems for quality improvement, and being open and responsive to criticism
9 Continuity by ensuring that responsibility for reviews, editorial processes, and key functions is maintained and renewed
10 Enabling wide participation in our work by reducing barriers to contributing and by encouraging diversity

Cochrane and its contributors do not accept commercial or conflicted funding. This allows Cochrane to produce authoritative and reliable information free from any possible bias resulting from commercial or financial interests. Cochrane and its contributors do not accept commercial or conflicted funding. This allows Cochrane to produce authoritative and reliable information free from any possible bias resulting from commercial or financial interests.

Cochrane Review Groups

Cochrane’s primary function is the preparation and maintenance of systematic reviews. This is the responsibility of more than 50 Cochrane Review Groups (CRGs) worldwide, each focused on a specific topic of health research. Examples of CRGs are the Breast Cancer Group, Dementia and Cognitive Improvement Group, Drugs and Alcohol Group, HIV/AIDS Group, Incontinence Group, Neonatal Group, Oral Health Group, Stroke Group and the Wounds Group. A list of CRGs and links to their webpages is available here.

Cochrane systematic reviews

Cochrane’s reviews of primary research in health care and health policy are internationally recognised as the highest standard in evidence-based health care resources. There are five types of Cochrane Review.

  • Intervention reviews assess the benefits and harms of interventions used in healthcare and health policy.
  • Diagnostic test accuracy reviews assess how well a diagnostic test performs in diagnosing and detecting a particular disease.
  • Methodology reviews address issues relevant to how systematic reviews and clinical trials are conducted and reported.
  • Qualitative reviews synthesise qualitative evidence to address questions on aspects other than effectiveness.
  • Prognosis reviews address the probable course or future outcome(s) of people with a health problem.

Each systematic review addresses a clearly constructed question, such as ‘what is the effect of immunisation with influenza vaccines on preventing influenza A or B infections and influenza-like illness and its consequences in healthy adults?’

To answer a question, Cochrane Reviewers find and collate all the primary research on a topic that meets predefined eligibility criteria. The research is then assessed, using stringent guidelines, to establish whether there is conclusive evidence about a specific treatment.

Cochrane Reviewers reduce the impact of bias across the review process using methods including:

  • Identification of relevant studies from multiple sources (including unpublished sources)
  • Selection of studies for inclusion and evaluation of their strengths and limitations on the basis of clear, predefined criteria
  • Systematic collection of data and
  • Appropriate synthesis of data.

These methods are described in detail in the Cochrane Handbook for Systematic Reviews of Interventions and the Cochrane Handbook for Diagnostic Test Accuracy Reviews.

Cochrane Reviews are peer-reviewed and updated regularly to incorporate new research, so that healthcare decisions can be based on the most up-to-date and reliable evidence. Reviews are published online in the Cochrane Library. Plain-language summaries of Cochrane Reviews can be found here.

Cochrane also publishes the Cochrane Database of Systematic Reviews (CDSR), a journal that includes Cochrane systematic reviews, protocols for Cochrane Reviews, and editorials. The CDSR is updated regularly as Reviews are published.

In the past 12 months (issue 10 2016 to issue 9 2017), the CDRS published 379 new reviews and 334 updated reviews. Twenty-seven reviews were withdrawn, and in 104 the conclusions were changed as a result of new evidence.

Cochrane’s influence on health

Cochrane’s independence, methodological rigour and focus on international collaboration mean that its evidence is universally regarded as highly authoritative, and therefore is frequently used to guide health interventions and shape health policy.


A Cochrane Review published in 1998 found that bednets impregnated with insecticide reduced child deaths by about one-fifth in malarial areas in Africa. Since then, the Cochrane Infectious Diseases Group malaria portfolio has expanded to over 70 reviews, assessing the evidence related mainly to malaria chemoprevention and chemotherapy. Fourteen Cochrane Reviews were used in formulating recommendations in the World Health Organization’s Guidelines for the Treatment of Malaria.


In 2015, the Cochrane Public Health Group published a Review containing evidence that people consume more food or non-alcoholic drinks when offered larger sized portions or when they use larger items of tableware. The evidence from this Review was one of the most cited public health stories of 2015, informing Public Health England’s report on sugar reduction and continuing to influence the debate on tackling obesity.

Catheters in hospital patients

Many hospital patients receive fluids or medications via an intravenous catheter. A Cochrane Review initially published in 2010 and updated in 2013 and 2015 produced significant evidence that routinely changing or replacing peripheral venous catheters is no better than replacing them when clinically indicated. It was estimated that acting on this evidence would a save the UK’s National Health Service £40 million over a five-year period.

  • About the author: Campbell Aitken
  • Dr Campbell Aitken is a freelance editor and a senior research fellow at the Burnet Institute.

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