How many Cochrane reviews are needed? Too many

PubMed Trend is a neat way to assess time treds in the Medline database. The number of Randomized controlled trials published per year continues to rise and has broken through the 33,000 barrier.

A 2003 analysis, of 989 Cochrane reviews which included information on a total of 9,778 studies, found the number of studies per review ranged from 0–136, with a median of 6 (interquartile range 3 to 12).

At the time of this analysis the average Cochrane review included 6 studies, and it was estimated that 45 000 Cochrane reviews would be needed to cover the existing 300 000 references.

By 2012 the cumulative total of trials in PubMed is 454 000: the number of reviews currently required is 75,700.

In terms of modelling the growth of trials a steady state will probably be arrived at by 2021, when approximately 50,000 trials will be added to the PubMed database each year.

The scary fact is, that at current rates we can expect as many trials to be published in the next ten years as have ever been published. Now that’s a lot of Cochrane reviews to be done.