A review of data sharing statements in observational studies

In order to understand the current state of data sharing in observational research studies, we reviewed data sharing statements of observational studies published in a general medical journal, the British Medical Journal. We found that the majority (63%) of observational studies published between 2015 and 2017 included a statement that implied that data used in the study could not be shared. If the findings of our exploratory study are confirmed, room for improvement in the sharing of real-world or observational research data exists.


References Introduction
Over the recent years, a number of articles and movements have called for the sharing of clinical trial data 1-3 . However the access to and sharing of real-world/observational data receives little and arguably insufficient attention. In this study we sought to assess the current state of data sharing in published observational studies in a general medical journal, namely the British Medical Journal (BMJ). The BMJ was chosen as the journal does not enforce a commitment of data sharing for observational studies 4 , but all research articles are required to contain a data sharing statement 5 .

Methods
All observational research articles published in the BMJ between 1 st January 2015 and 31 st August 2017 were investigated. These dates were chosen as it provides a reasonable sample size for analysis and recent data post-dating some of the articles regarding clinical trial data sharing 2 . Observational research articles were defined as cohort, case-control and cross-sectional studies, as well as case series. Meta-analyses, systematic reviews, randomised controlled trials and genetic/Mendelian randomisation studies were excluded. The data sharing statements of these studies were reviewed. If the statement written was "no additional data available" 5 or that data was not publicly available, the study data was classed as not shared. Statements alluding to data being available from the corresponding author, or a referral to access policies of the data source the study data was classed as shared. Where statements alluded to code or technical appendix being available, but no reference to data specifically being available, the study data was classed as not shared.

Results
Two hundred and thirty seven observational studies were included. A review of the data sharing statements of these studies revealed that 149 (63%) studies had a statement implying that the data underlying the study could not be shared.

Conclusions
In our review of the data sharing statements of observational studies published in the BMJ, we identified that the majority of studies did not share data. Whilst there are likely many reasons for this, including patient confidentiality concerns and the access possibilities of the data source, the lack of data sharing in observational research is a potential cause for concern. The key limitation of our study was the scope of the data. We only reviewed the data sharing statements of one medical journal and therefore the generalisability of our results is unclear. Our analysis should be seen as exploratory rather than definitive. Further studies are needed, in greater depth, to confirm or refute our findings. If consistent findings are seen, the lack of sharing of observational research data is an area that warrants further attention.

Data availability
Dataset 1: Raw data showing the studies identified from the BMJ and whether the data sharing statements indicated data was not/were available. doi, 10.5256/f1000research.12673.d177871 6 Competing interests LM and SR are employees of Bristol-Myers Squibb Company. AS, AS, SG and RW are employees of Evidera Inc.

Grant information
The author(s) declared that no grants were involved in supporting this work.

Are sufficient details of methods and analysis provided to allow replication by others? Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility? Yes

Are the conclusions drawn adequately supported by the results? Yes
No competing interests were disclosed.

Competing Interests:
I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
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