| Date | Event | Description |
|---|---|---|
| 17 March 2009 | New search has been performed | Updated, new studies included, tables & figures updated |
| 30 October 2008 | Amended | Converted to new review format. |
| 10 January 2006 | Amended | Minor update |
| 21 December 2005 | Amended | New studies found and included or excluded (seven abstracts reviewed ‐ five excluded (see characteristics of excluded studies) and two awaiting further details (see studies awaiting assessment)) |
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