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The Cochrane Collaboration

Abstract

The Cochrane Collaboration is an international, not–for–profit organisation that aims to help people make well–informed decisions about health care by preparing, maintaining and promoting the accessibility of systematic reviews of the effects of health-care interventions. Cochrane systematic reviews are prepared according to predefined, explicit methodology, and published in The Cochrane Library. The abstracts and plain English summaries of the reviews are freely available on the Internet. All reviews are prepared and maintained under the editorial control of 50 Cochrane Collaborative Review Groups that focus on (groups of) health problems. The work of Collaborative Review Groups is supported, among others, by people working in Cochrane Fields. Cochrane Fields focus on dimensions of health care other than health problems. To date, the issue of nutrition has not been addressed sufficiently in The Cochrane Collaboration. Nutrition issues are very important for day-to-day health care and the initiatives to establish a new Cochrane Diet and Nutrition (Sub)Field will help to promote the preparation of systematic reviews of nutritional interventions by the variety of Collaborative Review Groups to whom such interventions are relevant. Many issues regarding nutritional interventions, however, are complex, and methodological challenges will have to be overcome. A Cochrane Diet and Nutrition (Sub)Field with experts on nutritional research can help fill this gap and make those reviews more possible.

Introduction

The Cochrane Collaboration is an international, not–for–profit organisation that aims to help people make well–informed decisions about health care by preparing, maintaining and promoting the accessibility of systematic reviews of the effects of health-care interventions.

The Cochrane Collaboration is named after the epidemiologist, Archie Cochrane (1909–1988), a British medical researcher who contributed greatly to the development of epidemiology as a science. In the 1970s, he made a strong plea for creating critical summaries of all relevant randomised controlled trials of the effect of healthc-are interventions (Cochrane, 1972). This idea of systematically reviewing the medical literature was adopted by Sir Iain Chalmers who, in 1993, started the first Cochrane Centre in the UK. In the next couple of years, he and others established the international Cochrane Collaboration.

Much information about The Cochrane Collaboration can be found in the Newcomers' Guide on www.cochrane.org/docs/newcomersguide.htm. In this article, we highlight various aspects of The Cochrane Collaboration, including the possible role of a new Cochrane Diet & Nutrition Field.

Cochrane reviews

Cochrane Reviews are systematic, up-to-date assessments of evidence of the effects of health-care interventions, intended to help people to make informed decisions about health care, their own or someone else's. A Cochrane systematic review is prepared according to predefined, explicit methodology. The methods to be used are described in a protocol that is refereed, approved by editors and published in The Cochrane Library. The protocol sets out how the review will be conducted, in particular the methods to be used to minimise bias in all parts of the process: identifying relevant studies, selecting them for inclusion, and collecting and combining their data. Studies for consideration for the review should be sought regardless of their results.

If the identified studies are sufficiently similar with respect to the participants, interventions and outcomes, study results can be combined into an overall estimate of the relative effect of one intervention compared to another. This statistical combination of the results of separate studies is called meta-analysis. A systematic review, however, does not need to contain a statistical synthesis of the results from the included studies. This might be impossible if the designs of the studies are too different for an average of their results to be meaningful or if the outcomes measured are not sufficiently similar.

Cochrane Protocols and the Cochrane Reviews that follow them are published in full in The Cochrane Database of Systematic Reviews, one of several databases in The Cochrane Library, published electronically by John Wiley and Sons (www.thecochranelibrary.com). These protocols and reviews of health-care interventions are prepared and maintained under the editorial control of the Cochrane Collaborative Review Groups. The Cochrane Database of Systematic Reviews includes a Comments and Criticisms System to enable users to help improve the quality of Cochrane Reviews. Abstracts and consumer summaries of Cochrane Reviews are freely available to everyone on the Internet on both The Cochrane Collaboration's website (www.cochrane.org/reviews/clibintro.htm#abstracts) and also within the free sections of The Cochrane Library (www.thecochranelibrary.com).

In addition to Cochrane Reviews, The Cochrane Library contains a number of additional databases among which are The Database of Abstracts of Reviews of Effects (DARE) and The Cochrane Central Register of Controlled Trials (CENTRAL) (www.thecochranelibrary.com). DARE is assembled and maintained by the Centre for Reviews and Dissemination in York, UK, and contains critical assessments and structured abstracts of other systematic reviews, conforming to explicit quality criteria. CENTRAL contains bibliographic information on hundreds of thousands of controlled trials, including reports published in conference proceedings and many other sources not currently listed in other bibliographic databases.

The Cochrane Collaboration's principles

The Cochrane Collaboration's work is based on key principles (www.cochrane.org/docs/tenprinciples.doc). The first of these is ‘Collaboration’. The enormous efforts of The Cochrane Collaboration cannot be achieved without people cooperating with each other, setting aside self-interest, and working together to provide evidence with which to improve health care. In addition, worldwide collaboration ensures the aims of The Cochrane Collaboration will be met in a very efficient way. The second principle is about ‘Building on the enthusiasm of individuals’. The organisation benefits from over 12 000 contributors in more than 90 countries, almost all of whom receive no payment for the work they do within the Collaboration. These people work collaboratively within one or more groups, called ‘Cochrane entities’ (see below) (Allen et al, 2004). The third principle concerns avoiding duplication of effort. Summarising existing evidence about the effect of health-care interventions is a huge task, and it would be a waste of time and resources if multiple members of the Collaboration sought to summarise the same body of evidence simultaneously but separately. By collaborating and working together on individual reviews or agreeing to work separately on reviews of different health-care topics, duplication of effort is prevented and the scarce resources can be used more efficiently.

Structure of The Cochrane Collaboration

The main work of The Cochrane Collaboration is done by 50 Collaborative Review Groups, with bases around the world, within which Cochrane Reviews are prepared and maintained. The members of these groups—researchers, health-care professionals, people using the health services (consumers), and others—have come together because they share an interest in generating reliable, up-to-date evidence relevant to the prevention, treatment and rehabilitation of particular health problems or groups of problems. These Collaborative Review Groups operate in a similar way to independent scientific journals: they have their own editorial board, which has responsibility for planning, coordinating and monitoring the Group's work (including the quality of the Cochrane Reviews), but they share a common goal of helping people make well-informed decisions about health care and use common techniques to do this.

The work of Collaborative Review Groups is supported by people working in Methods Groups, the Consumer Network, Cochrane Centres and Fields. Cochrane Methods Groups aim to improve the methods for reviewing, meta-analysis and other aspects of the evaluation of health care. The Cochrane Consumer Network provides information and a forum for networking among consumers involved in the Collaboration, and a liaison point for other consumer groups around the world. Cochrane Centres facilitate the review process in a variety of ways. They share responsibility for helping to co-ordinate and support members of the Collaboration in particular geographic areas through the provision of training, and they also promote the objectives of the Collaboration at national level. Finally, Cochrane Fields (or Networks) focus on dimensions of health care other than health problems. The work of Fields is described in more detail elsewhere in this issue (Lodge, 2005).

Nutrition and The Cochrane Collaboration

Many aspects of health care are covered adequately within the existing structure of the various Cochrane entities. However, to date the issue of nutrition has not been addressed sufficiently in The Cochrane Collaboration. Nutrition issues are very important for day-to-day health care and the initiatives of the Heelsum Group to establish either a new Cochrane Diet and Nutrition Field or a Subfield of an existing Field will help to promote the preparation of systematic reviews of nutritional interventions by the variety of Collaborative Review Groups to whom such interventions are relevant. These Groups include (amongst others) the Cochrane Heart Group (based in Bristol, UK), the Metabolic and Endocrine Disorders Group (Düsseldorf, Germany), the Colorectal Cancer Group and the Hepato-Biliary Group (Copenhagen, Denmark), the Hypertension Group (Vancouver, Canada), the Inflammatory Bowel Disease Group (London, Canada), the Stroke Group (Edinburgh, UK), the Upper Gastrointestinal and Pancreatic Diseases Group (Leeds, UK) and the Consumers and Communication Group (Melbourne, Australia). Many issues regarding nutritional interventions are complex, and methodological challenges will have to be overcome. A Cochrane Diet and Nutrition (Sub)Field with experts on nutritional research can help to fill this gap and make those reviews more possible.

References

  1. Allen C, Clarke M & Kitchener L (2004): International activity within collaborative review groups. Poster P-002, 12th annual Cochrane Colloquium, The Canadian Cochrane Network and Centre, Ottawa, Canada, 2–6 October, 2004.

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Correspondence to R J P M Scholten.

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Scholten, R., Clarke, M. & Hetherington, J. The Cochrane Collaboration. Eur J Clin Nutr 59, S147–S149 (2005). https://doi.org/10.1038/sj.ejcn.1602188

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