An important question that is as relevant to Q&A as to systematic reviews. This Annals of Internal Medicine article (click here) attempts to answer this question. The important bit, for me was this:
“This survival analysis of 100 meta-analyses indexed in ACP Journal Club from 1995 to 2005 found new evidence that substantively changed conclusions about the effectiveness or harms of therapies occurred frequently within relatively short time periods. The median survival time without substantive new evidence for the meta-analyses was 5.5 years. Significant new evidence was already available for 7% of the reviews at the time of publication and became available for 23% within 2 years.”
Trip Database Blog 
August 1, 2007 at 3:00 pm
Quite improtant work – and somehow frightening! Clinical guidelines don’t age that fast: http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=11572738&dopt=AbstractPlusMartin
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August 9, 2007 at 4:45 am
Hi Martin,Thanks for that an interesting paper from AHRQ. For the Q&A work we do we warn people about how dated the answers are after 2 years. It was an arbitary decision at the time, but seems fairly reasonable, in light of the paper I posted and the one you’ve highlighted.Best wishesjon
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August 10, 2007 at 11:06 am
We http://www.hta.uni-bremen.de disucussed both: one should be aware of the diffenence between a guideline’s recommendation and the conclusion of a systematic review. The first is usually much more conservative and therefore living longer, while the latter is often very focussed thus being more sensitive to new pieces of information. Q&A are somewhere inbetween. At http://www.klinpharm-bremen.de we do Q&A works as well, but on a more individual, less generalizable level. I can only guess, but your 2years margin seems conservative.Martin
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