The Cochrane Collaboration is a unique, worldwide not-for-profit organization 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.1 A decade ago, C. David Naylor referred to the Collaboration as the health services equivalent of the Human Genome Project.2 The present commentary reflects on progress to date and on remaining challenges.
The core business of the Cochrane Collaboration is to produce systematic reviews that are regularly updated and published quarterly (with other electronic resources) in the Cochrane Library. There were 2074 systematic reviews in the latest edition of the Cochrane Library (2004, issue 3). The coverage of Cochrane reviews is continually improving, and reviews now exist relevant to the top 10 causes of disability in both developed and developing countries. It has been demonstrated that Cochrane reviews are of comparable or better quality and are updated more often than reviews published in print journals.3 In addition, the Cochrane Library includes the Cochrane Central Register of Controlled Trials (CENTRAL), with over 415 000 references to completed and ongoing randomized controlled trials; the Cochrane Methodology Register, with over 5600 references to methodologic papers; and 3 other databases of systematic reviews, health technology assessment reports and economic evaluations.
These reviews are authored by about 7000 volunteers worldwide (researchers, health care professionals and consumers) and are supported by a range of Cochrane entities. This is the health services research equivalent of “distributed computing,”4 by which computationally intense activities are managed by sharing workload across networked computers to provide computing power equivalent to the fastest commercial supercomputers. The Cochrane Collaboration builds on the enthusiasm of individuals to undertake reviews, often within their own resources, using a standardized approach; this has led to the dramatic increase in Cochrane reviews with relatively little external funding (see Fig. 1). Cochrane authors make a commitment to update their reviews as new evidence becomes available and as comments and criticisms from users of the Cochrane Library are received. The Collaboration has promoted the involvement of consumers throughout the conduct of reviews, and reviews include consumer synopses written in lay language.
Through national licences, the Cochrane Library is available free of charge to users in Australia, Denmark, England, Finland, Ireland, Norway, Northern Ireland, South Afri ca, Spain and Wales. For users in countries classified by the World Bank as low- or middle-income the Cochrane Library is available through HINARI (the Health InterNetwork Access to Research Initiative). The Cochrane Library is published by John Wiley & Sons on CD-ROM and the Internet; on average, someone accesses this Web site every 37 seconds. Additional coverage is provided worldwide through partnerships with information aggregators such as Ovid Technologies and Silver Platter Information, which facilitate broader dissemination; for example, Ovid Technologies has over 5000 institutional customers worldwide with more than 2.5 million individual users.
Cochrane reviews have been used to develop a number of “knowledge translation” products for professionals, patients and policy-makers.5 Increasingly, these products are being labelled as having “Cochrane inside” (similar to the “Intel inside” label on personal computers). For example, Cochrane reviews provide the evidence base for the Reproductive Health Library, a WHO-sponsored electronic publication containing Cochrane reviews, guidelines and commentaries that is distributed free to over 34 000 professionals and health care organizations in low- and middle-income countries in both English and Spanish versions.6 Cochrane reviews are also an important source of evidence for Clinical Evidence, which is distributed free to over 50 000 professionals within the UK National Health Service, to professionals in the United States (BMJ Publishing, courtesy of the Unit Health Foundation) and via the Internet to over 100 low- and middle-income countries. All of these products are regularly updated using data from Cochrane reviews.
In Canada, Cochrane reviews are being used to support health technology reports prepared by the Coordinating Council of Health Technology Assessment and the work of the Therapeutics Initiative. They are consulted by the peer review panels of the Canadian Institutes of Health Research and are used in the preparation of clinical practice guidelines, such as those by the Canadian Paediatric Society.5
The work of the Cochrane Collaboration has also led to substantial methodologic advances. For example, an early product from the Collaboration led to the development of highly sensitive search strategies for randomized controlled trials.7 Cochrane reviews provided the data that demonstrated that failure to conceal randomization allocation was associated with bias.8The volume of Cochrane reviews produced using common methods within a standardized format9 ensures that the Cochrane Library is the best single resource for methodologic research and for developing the science of meta-epidemiology.