In 1995, the first edition of The Cochrane Database of Systematic Reviews included a few dozen Cochrane reviews. It has grown greatly since then and when the fourth and final issue of The Cochrane Library for 2009 was published in October, the Database saw the arrival of the 4000th full Cochrane review. These reviews are available in full at http://www.TheCochraneLibrary.com. The Issue includes nearly 250 Cochrane reviews that are either appearing in full for the first time or have been updated since the last edition in July. Each review contains full information on the methods used to prepare it, details and critical appraisal of the eligible research, results of the included studies and the conclusions of the Cochrane researchers on the implications for practice and research of their findings.
The new and updated Cochrane reviews investigate a wide range of health issues and a wide variety of interventions. They are accompanied by a large collection of Evidence Pods. These short audio recordings by the authors of the reviews, summarise what they did and what they found. They are all available in English, free of charge, on http://www.cochrane.org/podcasts and several of them have been translated into other languages, including Dutch, French, German and Italian. A summary for Issue 4 is also available on YouTube at http://www.youtube.com/watch?v=LBS-ZZZLWco.
The new reviews include a cluster from the Cochrane Musculoskeletal Group looking at a variety of treatments for arthritis. This includes one of the first Cochrane overviews of reviews which draws on six separate Cochrane reviews of a class of drugs called biologics, to provide an evidence base for comparing and contrasting these drugs in rheumatoid arthritis (1). This overview is also the feature of the first Cochrane Journal Club (http://www.cochranejournalclub.com). Within The Cochrane Library and the Evidence Pods, it is accompanied by new or updated reviews of exercise programmes for people with rheumatoid arthritis (2), and opioids (3) and transcutaneous electrostimulation, or TENS, for osteoarthritis of the knee (4). Another updated review presents the latest evidence on physical fitness training for people who have had a stroke (5). Among the large amount of new evidence on drug treatments, there is an updated review on antiviral treatment for Bell's palsy (6) and a new review of homocysteine lowering interventions for preventing cardiovascular events (7). Other new or updated reviews look at surgery for urinary incontinence in women (8), traffic calming for preventing traffic related injuries (9), and Chinese herbal medicines for people with impaired glucose tolerance (10). Two of the early Cochrane reviews from the 1990s have also been updated, providing up-to-date accounts of research into the drug treatment of hypertension in the elderly (11) and psychological treatments for bulimia nervosa (12).
After the first 50 full Cochrane reviews had appeared by 1996, there were 500 in 1999, 1000 in 2001, 2000 in 2004 and 3000 in 2007 (13). There are now 4000, through a tremendous global effort (14) which is continuing, producing new reviews and striving to keep the existing ones up to date and relevant. In the following section, some of the Cochrane authors who recorded podcasts for earlier issues of The Cochrane Library tell us about their reviews.