MEDLINE data changes for 2008 are explained in a recent National Library of Medicine Technical Bulletin, including information on changes made to MEDLINE during the annual NLM maintenance known as Year-End Processing (YEP).
MEDLINE/PubMed Year-End Processing (YEP) Activities. NLM Tech Bull. 2007 Sep-Oct;(358):e10 also explains how the current maintenance effort affects the NLM schedule for adding indexed MEDLINE citations to PubMed.
This article links to two additional resources: Annual MEDLINE/PubMed Year-End Processing (YEP): Impact on Searching During Fall 2007 and Annual MEDLINE/PubMed Year-End Processing (YEP): Background Information, which has examples of the typical changes that take place for MEDLINE citations during year-end processing.
In other MEDLINE news, beginning December 28, 2007, 55,557 citations from the 1949 Current List of Medical Literature (CLML) were added to the OLDMEDLINE subset in PubMed. These citations have not yet been mapped to current MeSH. To search PubMed for citations originating from OLDMEDLINE data, use jsubsetom.