Search complete

The timeline in my proposal says today is the deadline for completing the search. Here’s what the proposal says about the search:

Databases searched for this study will be restricted to the Cochrane Central Register of Controlled Trials (CENTRAL). Since 1998, Cochrane review groups have completed 11 systematic reviews of vitamin D supplementation on pregnancy, infection prevention in children, management of asthma, treatment of chronic pain in adults, mortality (2), cancer prevention, fracture prevention, cystic fibrosis, bone mineral density in children, and corticosteroid-induced osteoporosis. The most recent study on mortality includes more trials than any other vitamin D systematic review ever published.

CENTRAL contains a record for every study examined in its own reviews. In addition, CENTRAL is updated monthly with records of new randomized controlled trials retrieved from Medline and EMBASE, from specialized registers created by Cochrane’s review groups, and from Cochrane’s hand search results register. Because of the comprehensive nature of CENTRAL’s database of randomized controlled trials, CENTRAL by itself can provide a systematic view of all relevant randomized controlled trials in both the primary and the grey literature. This avoids the additional work of stage 1 reviews finding duplicative results in additional databases that are a mix of randomized controlled trials and other types of publications, making this project feasible for a single author. Complete information on the contents of CENTRAL and how it is updated is available at

Any other vitamin D3 trials not discovered by this process may be included in the study. The discovery method of each trial will be recorded. CENTRAL will be notified of any trials missing from its database.

Search strategy. The CENTRAL search strategy will use the MeSH descriptor [Vitamin D] explode all trees. Adding additional vitamin D-related MeSH terms does not increase the number of records returned by CENTRAL. Adding additional vitamin-D related text terms vastly increases the number of records returned, but the author does not have the resources to review that many papers, particularly since almost all will fail stage 1 review anyhow (these are trials in which vitamin D is mentioned somewhere in the full text; the MeSH descriptor identifies trials that are actually about vitamin D). All trials returned by the MeSH search will be reviewed for eligibility without further limits. CENTRAL is limited to trials in humans by design. Based on preliminary testing of this strategy, CENTRAL will provide records for more than 2,750 journal articles.

At the Cochrane Central Register of Controlled Trials, I clicked on the Medical Terms (MeSH) tab, entered vitamin D, and clicked the Lookup button. A results summary appeared in the rightmost column on the page that appeared.

There are 2,707 results for your search on MeSH descriptor: [Vitamin D] explode all trees.

Of these, 2,470 are trials, 26 are Cochrane reviews, 147 are other reviews, and 64 are other types of documents.

Next I clicked on the View Results button and the first section of documents appeared at the bottom of the page. To their left was a set of radio buttons, where I selected Trials (2,470) – the only results I’m interested in. Then, just above the first result I clicked the words Export all. In the dialog that appeared, I selected my operating system and Citation and abstract, then clicked Export Citation. Finally I selected a folder on my own computer to save the file in.

After the download, I opened the file in Notebook (it’s too big to open in RStudio) and there were the 2,470 records with abstracts and PubMed ids. Search complete.

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