Structured abstracts contain distinct labeled sections (e.g., “RESULTS”). The MEDLINE/PubMed database incorporates English-language abstracts that appear in the journals that the US National Library of Medicine (NLM) indexes. If English-language structured abstracts appear in a journal that is indexed, the labels in these abstracts usually appear in all uppercase letters, generally followed by a colon, in MEDLINE/PubMed citations .
Several years after formats for more informative abstracts were proposed [2–,5], NLM studied the structured abstracts that appeared in MEDLINE from 1989–1991 as an initial step in exploring their utility in enhancing bibliographic retrieval . This early study showed that structured abstracts were an emerging, but rapidly growing phenomenon; that MEDLINE records with structured abstracts tended to have more access points (Medical Subject Headings [MeSH] terms and text words) than MEDLINE records as a whole; and that there was significant variation in the structured abstract formats that different journals prescribed.
Implementation of structured abstracts by biomedical journals has been examined on a small scale in the clinical medicine domain [7, 8], but no large-scale examination across all of MEDLINE has occurred since the first exploratory study by NLM. Hence, the objective of this study was to conduct a retrospective cohort study to measure and characterize the growth in structured abstracts in MEDLINE since 1991, with a view, again, toward exploring their utility in enhancing information display and retrieval.