Several vaping papers may report one study: check before counting confirmations

A citation count answers the wrong first question

A webpage may list several references after one claim. The references might include an initial report, a later follow-up and an analysis of another outcome in the same participants. Each can contain useful information, but the number of documents does not establish how many independent groups were studied.

Cochrane’s study-selection guidance distinguishes reports from studies and says related reports should be linked rather than treated as separate studies. We use that methods principle for a reader’s citation check. This is not an assessment of a named vaping intervention or a shortcut for conducting a systematic review.

Cochrane: Cochrane Handbook, Chapter 4: Searching for and selecting studies

Make a report-to-study map

Create one row per document with its title, identifier, described participants and any statement connecting it to another publication. Look for a trial registration number when relevant, the recruitment setting and dates, and whether authors identify a follow-up or secondary analysis. Leave missing details blank.

A shared author list alone does not prove shared participants. Different authors or titles do not prove independence either. If the relationship remains unclear, record “study relationship not established.” You can ask for clarification without accusing anyone of duplicate publication or attempting to identify individual participants.

Use a hypothetical reading example

Imagine three papers: one describes an initial intervention comparison, a second follows the same group later, and a third examines a different reported outcome in that group. If the papers explicitly establish that connection, your map has three reports attached to one study. The later papers may add important information about time or outcomes.

Now imagine a fourth paper that describes separately recruited participants at another site. Do not merge it solely because it evaluates a similarly named program. Record the details that establish its relationship or independence. This example contains no actual study findings, sample sizes or success rates; it shows why neither automatic addition nor automatic deletion is a sound first step.

Preserve the value of the linked reports

Do not discard the follow-up as worthless because it shares participants. It may answer a question the first paper did not address. Cite the report you actually read for the specific outcome and time point, while keeping its connection visible. Avoid combining its percentage with an earlier percentage as if they came from different people.

This differs from checking a preprint against its later journal version: reports can be genuinely different publications and still share an underlying study. A more complex dataset may also contain partially overlapping samples. This small map cannot resolve every overlap or recalculate a pooled estimate.

State a narrower conclusion

You can say: “These references include several reports from one identified study; I have not established several independent confirmations.” If you cannot identify the relationships, leave the confirmation count unknown. Finding one linked set does not prove that all evidence on the subject has the same limitation.

For a health decision, bring the claim and the original documents to an appropriate professional rather than turning your map into a treatment ranking. For ordinary reading, stop when you can describe what the references represent and what remains uncertain. The useful output is a transparent source map, not a numerical verdict about whether you should use a product.