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Table 1 An independent inquiry into inequalities in health - an example of the need for up-to-date systematic reviews to know what evidence there is

From: SUPPORT Tools for evidence-informed health Policymaking (STP) 17: Dealing with insufficient research evidence

In 1997, the incoming British Labour government was keen to reduce inequalities in health. To do this, it set about obtaining advice from the public health community about how to reduce inequalities, but clear limits were set about what advice it would find acceptable. The government wanted the advice quickly but stipulated that the advice had to be backed by evidence, in keeping with the government's expressed desire that public policy should be based on evidence [31]. The public health and other communities responded enthusiastically. A considerable amount of material was produced by, and for, the inquiry and many recommendations were made [32].

Subsequent reviews of the recommendations, however, found little evidence for the likely or actual effectiveness of many of the recommendations [32]. There was also a striking lack of adequate searches for relevant evidence or attempts to avoid bias in the way information was identified, appraised, and used.

This is not to suggest that governments cannot develop or implement policies that lack the support of unequivocal evidence. A lack of evidence does make it difficult, however, for them to decide on priorities. The readiness of researchers to recommend policies while knowing little about the likely effectiveness makes this more difficult still.

The task of this particular inquiry in the United Kingdom would have been easier if up-to-date systematic reviews had been available. Further, a system to ensure that the inquiry's recommendations would be reviewed regularly as new information and evidence emerged from updated systematic reviews, would have helped to ensure that adjustments in policies could have been made. This could also have helped to avoid similar future difficulties when similar inquiries were undertaken or similar policies considered in other jurisdictions. International networks such as The Cochrane Collaboration http://www.cochrane.org (which focuses on healthcare) and the Campbell Collaboration http://www.campbellcollaboration.org (which focuses on education, crime and justice, and social welfare) have structures for preparing and keeping systematic reviews up-to-date, and these can facilitate the more effective use of evidence.

The investment of public resources in primary research has been substantial and remains so. But the returns remain far less than might otherwise have been expected, and the results scattered rather than synthesised. People faced with tasks and timescales similar to those of the British inquiry would be assisted greatly if up-to-date systematic reviews were more readily available. In terms of developing health policies and programmes, there are no unequivocal answers to the question "What works?" A systematic review is the best starting point for finding out what is known.