Why do we want to know the years of coverage?
It is helpful to know which publication years have been searched, particularly in the context of systematic reviews. This is an indication of the completeness of a search.
The 2020 PRISMA Statement advises researchers to include the years of coverage of databases searched, where provided. It suggests including a table of database coverage.
We suggest you don't copy the dates of coverage from the sample table in PRISMA 2020, as some of the dates are incorrect or may refer to something else.
It is a common misunderstanding that names of databases that include dates reflect their years of coverage, but this is rarely the case. Older content is often added retrospectively and pre-print publications are often added in advance. This means years of coverage are fluid - constantly changing.
For example, in the database Ovid MEDLINE(R) ALL 1946 to August 28, 2023:
"But the official Medline Database Guide shows coverage from 1946!"
Unfortunately publisher sites can sometimes be confusing, and in the case of the Medline 2022 Database Guide this probably relates to their definition of "Years of coverage". Rather than the publication years of CONTENT, these "years of coverage" seem to refer to versions of the database or catalogue, which HOLD the content, or perhaps the date a record was indexed. Just be aware that these are quite different things to publication dates.
Need some proof about date ranges?
Try a little experiment in Ovid Medline ALL which is often described as covering 1946 to the present.
Method 1: Scroll the drop down year limits to find the oldest year you can limit to eg 1860.
Method 2: Search using the Year of Publication field (.yr) to find the oldest year where you get results eg 17*.yr. will retrieve records from the 1700s (over 600 results in Medline).
The oldest publication will probably be on the last page like this:
Years of coverage are constantly changing in most databases, and old publications are often added retrospectively. This is the best indication of coverage that we have been able to research, as at 29 July 2022. We checked official database guides and also ran tests in each database, including checking provided year limits. Please note that there appears to be no definitive answer.
Ovid MEDLINE(R) ALL 1946 to present
Embase 1974 to present (Ovid)
Ovid Emcare 1995 to present
Ovid Nursing Database 1946 to present
APA PsycINFO (Ovid)
CINAHL (EBSCOhost)
Cochrane Library
If coverage constantly changes, how do we accurately record what we searched?
For many bibliographic databases it is not possible to accurately define the years of coverage. That is why we keep these records for systematic reviews:
If you need to add a table of database of years of coverage (as per PRISMA 2020)
"If bibliographic databases were searched, specify for each database its name (such as MEDLINE, CINAHL), the interface or platform through which the database was searched (such as Ovid, EBSCOhost), and the dates of coverage (where this information is provided).
From Page M J, Moher D, Bossuyt P M, Boutron I, Hoffmann T C, Mulrow C D et al. PRISMA 2020 explanation and elaboration: updated guidance and exemplars for reporting systematic reviews BMJ 2021; 372 :n160 doi:10.1136/bmj.n160
There are a few options around how to respond to this requirement from PRISMA 2020. One is to decide whether the dates of coverage have actually been provided. If not, then you can simply provide the complete name of the databases eg Ovid MEDLINE(R) ALL 1946 to July 27, 2022. If the database name doesn't include the platform then just add it in brackets at the end eg Embase 1974 to 2022 July 27 (Ovid). Both of these show exactly what you searched.
If you want to create a table more like the example provided in PRISMA 2020, and try to explain years of coverage, then it might look something like this:
| Full name of database | Platform | Years of coverage |
| Ovid MEDLINE(R) ALL 1946 to July 27, 2022 | Ovid | Indexed retrospectively from 1946 to present, including pre-prints, with publications dating back to 1781. The range of publication dates is fluid and does not indicate complete journal coverage for all years. |
| Embase 1974 to 2022 July 27 | Ovid | Indexed retrospectively from 1974 to present, including pre-prints, with publications dating back to 1883. The range of publication dates is fluid and does not indicate complete journal coverage for all years. |
Or, if you want to include more data at the same time, all of which relates to dates, you might do something like this:
| Full name of database | Platform | Years of coverage in database | Date limits applied in search, if any | Date searched | Number of results | Date range of retrieved publications* |
| Ovid MEDLINE(R) ALL 1946 to July 27, 2022 | Ovid | Indexed retrospectively from 1946 to present, including pre-prints, with publications dating back to 1781. The range of publication dates is fluid and does not indicate complete journal coverage for all years. | No date limits applied | 29 July 2022 | 457 | 1976 - 2023 |
| Embase 1974 to 2022 July 27 | Ovid | Indexed retrospectively from 1974 to present, including pre-prints, with publications dating back to 1883. The range of publication dates is fluid and does not indicate complete journal coverage for all years. | No date limits applied | 29 July 2022 | 650 | 1971 - 2022 |
*This is not a PRISMA requirement, but could be interesting if you can easily work out the date range from records exported to EndNote before deduping.